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  • 1.
    Alling, Björn
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Steneget, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Tholander, Christopher
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Configurational disorder effects on adatom mobilities on Ti1-xAlxN(001) surfaces from first principles2012In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 24, p. 245422-Article in journal (Refereed)
    Abstract [en]

    We use metastable NaCl-structure Ti0.5Al0.5N alloys to probe effects of configurational disorder on adatom surface diffusion dynamics which control phase stability and nanostructural evolution during film growth. First-principles calculations were employed to obtain energy potential maps of Ti and Al adsorption on an ordered TiN(001) reference surface and a disordered Ti0.5Al0.5N(001) solid-solution surface. The energetics of adatom migration on these surfaces are determined and compared to isolate effects of configurational disorder. The results show that alloy surface disorder dramatically reduces Ti adatom mobilities. Al adatoms, in sharp contrast, experience only small disorder-induced differences in migration dynamics.

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  • 2.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dorri, Samira
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kooijman, Agnieszka
    Department of Materials Science and Engineering, Delft University of Technology, Delft, the Netherlands.
    Wu, Zhengtao
    School of Electromechanical Engineering, Guangdong University of Technology, Guangzhou, China.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mol, Johannes M.C.
    Department of Materials Science and Engineering, Delft University of Technology, Delft, the Netherlands.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana, IL, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan .
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana, IL, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan .
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Multifunctional ZrB2-rich Zr1-xCrxBy thin films with enhanced mechanical, oxidation, and corrosion properties2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 185, article id 109990Article in journal (Refereed)
    Abstract [en]

    Refractory transition-metal (TM) diborides have high melting points, excellent hardness, and good  chemical  stability.  However, these properties are not sufficient for applications involving extreme  environments that require high mechanical strength as well as oxidation and corrosion resistance. Here, we study the effect of Cr addition on the properties of ZrB2-rich Zr1-xCrxBy thin films grown by hybrid high-power impulse and dc magnetron co-sputtering (Cr-HiPIMS/ZrB2-DCMS) with a 100-V Cr-metal-ion synchronized potential. Cr metal fraction, x = Cr/(Zr+Cr), is increased from 0.23 to 0.44 by decreasing the power Pzrb2 applied to the DCMS ZrB2 target from 4000 to 2000 W, while the average power, pulse width, and frequency applied to the HiPIMS Cr target are maintained constant. In addition, y decreases from 2.18 to 1.11 as a function of Pzrb2, as a result of supplying Cr to the growing film and preferential B resputtering caused by the pulsed Cr-ion flux. ZrB2.18, Zr0.77Cr0.23B1.52, Zr0.71Cr0.29B1.42, and Zr0.68Cr0.32B1.38 2 films have hexagonal AlB2 crystal structure with a columnar nanostructure, while Zr0.64Cr0.36B1.30 and Zr0.56Cr0.44B1.11 are  amorphous. All films show hardness above 30 GPa. Zr0.56Cr0.44B1.11 alloys exhibit much better toughness, wear, oxidation, and corrosion resistance than ZrB2.18. This combination of properties   makes Zr0.56Cr0.44B1.11 ideal candidates for numerous strategic applications.

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  • 3.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dorri, Samira
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kosari, Ali
    Delft Univ Technol, Netherlands.
    Mol, Arjan
    Delft Univ Technol, Netherlands.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci & Technol, Taiwan.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Microstructure, mechanical, and corrosion properties of Zr1-xCrxBy diboride alloy thin films grown by hybrid high power impulse/DC magnetron co-sputtering2022In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 591, article id 153164Article in journal (Refereed)
    Abstract [en]

    We study microstructure, mechanical, and corrosion properties of Zr1-xCrxBy coatings deposited by hybrid high power impulse/DC magnetron co-sputtering (CrB2-HiPIMS/ZrB2-DCMS). Cr/(Zr + Cr) ratio, x, increases from 0.13 to 0.9, while B/(Zr + Cr) ratio, y, decreases from 2.92 to 1.81. As reference, ZrB2.18 and CrB1.81 layers are grown at 4000 W DCMS. ZrB2.18 and CrB1.81 columns are continual from near substrate toward the surface with open column boundaries. We find that the critical growth parameter to achieve dense films is the ratio of Cr+- dominated ion flux and the (Zr + B) neutral flux from the ZrB2 target. Thus, the alloys are categorized in two groups: films with x < 0.32 (low Cr+/(Zr + B) ratios) that have continuous columnar growth, rough surfaces, and open column boundaries, and films with x >= 0.32 (high Cr+/(Zr + B) ratios) that Cr+-dominated ion fluxes are sufficient to interrupt continuous columns, resulting in smooth surface and dense fine-grain microstructure. The pulsed metal-ion irradiation is more effective in film densification than continuous Ar+ bombardment. Dense Zr0.46Cr0.54B2.40 and Zr0.10Cr0.90B1.81 alloys are hard (> 30 GPa) and almost stress-free with relative nano indentation toughness of 1.3 MPa root m and 2.3 MPa root m, respectively, and remarkedly low corrosion rates (~& nbsp;1.0 x 10(-6) mA/cm(2) for Zr0.46Cr0.54B2.40 and~& nbsp; 2.1 x 10(-6) mA/cm(2) for Zr0.10Cr0.90B1.81).

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  • 4.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Engberg, David
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Strategy for simultaneously increasing both hardness and toughness in ZrB2-rich Zr1-xTaxBy thin films2019In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 3, article id 031506Article in journal (Refereed)
    Abstract [en]

    Refractory transition-metal diborides exhibit inherent hardness. However, this is not always sufficient to prevent failure in applications involving high mechanical and thermal stress, since hardness is typically accompanied by brittleness leading to crack formation and propagation. Toughness, the combination of hardness and ductility, is required to avoid brittle fracture. Here, the authors demonstrate a strategy for simultaneously enhancing both hardness and ductility of ZrB2-rich thin films grown in pure Ar on Al2O3(0001) and Si(001) substrates at 475 degrees C. ZrB2.4 layers are deposited by dc magnetron sputtering (DCMS) from a ZrB2 target, while Zr1-xTaxBy alloy films are grown, thus varying the B/metal ratio as a function of x, by adding pulsed high-power impulse magnetron sputtering (HiPIMS) from a Ta target to deposit Zr1-xTaxBy alloy films using hybrid Ta-HiPIMS/ZrB2-DCMS sputtering with a substrate bias synchronized to the metal-rich portion of each HiPIMS pulse. The average power P-Ta (and pulse frequency) applied to the HiPIMS Ta target is varied from 0 to 1800W (0 to 300 Hz) in increments of 600W (100 Hz). The resulting boron-to-metal ratio, y = B/(Zr+Ta), in as-deposited Zr1-xTaxBy films decreases from 2.4 to 1.5 as P-Ta is increased from 0 to 1800W, while x increases from 0 to 0.3. A combination of x-ray diffraction (XRD), glancing-angle XRD, transmission electron microscopy (TEM), analytical Z-contrast scanning TEM, electron energy-loss spectroscopy, energy-dispersive x-ray spectroscopy, x-ray photoelectron spectroscopy, and atom-probe tomography reveals that all films have the hexagonal AlB2 crystal structure with a columnar nanostructure, in which the column boundaries of layers with 0 amp;lt;= x amp;lt; 0.2 are B-rich, whereas those with x amp;gt;= 0.2 are Ta-rich. The nanostructural transition, combined with changes in average column widths, results in an similar to 20% increase in hardness, from 35 to 42 GPa, with a simultaneous increase of similar to 30% in nanoindentation toughness, from 4.0 to 5.2MPa root m. Published by the AVS.

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  • 5.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mráz, Stanislav
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schneider, Jochen M.
    Materials Chemistry, RWTH Aachen University, Aachen, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana, IL, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dense Ti0.67Hf0.33B1.7 thin films grown by hybrid HfB2-HiPIMS/TiB2-DCMS co-sputtering without external heating2021In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 186, article id 110057Article in journal (Refereed)
    Abstract [en]

    There is a need for developing synthesis techniques that allow the growth of high-quality functional films at low substrate temperatures to minimize energy consumption and enable coating temperature-sensitive substrates. A typical shortcoming of conventional low-temperature growth strategies is insufficient atomic mobility, which leads to porous microstructures with impurity incorporation due to atmosphere exposure, and, in turn, poor mechanical properties. Here, we report the synthesis of dense Ti0.67Hf0.33B1.7 thin films with a hardness of ∼41.0 GPa grown without external heating (substrate temperature below ∼100 °C) by hybrid high-power impulse and dc magnetron co-sputtering (HfB2-HiPIMS/TiB2-DCMS) in pure Ar on Al2O3(0001) substrates. A substrate bias potential of −300 V is synchronized to the target-ion-rich portion of each HiPIMS pulse. The limited atomic mobility inherent to such desired low-temperature deposition is compensated for by heavy-mass ion (Hf+) irradiation promoting the growth of dense Ti0.67Hf0.33B1.7.

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  • 6.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O.Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Rosen, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana IL 61801, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, Urbana IL 61801, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taipei 10607, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Self-organized columnar Zr0.7Ta0.3B1.5 core/shell-nanostructure thin films2020In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 401, article id 126237Article in journal (Refereed)
    Abstract [en]

    We recently showed that Zr1−xTaxBy thin films have columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. Layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we determine the atomic-scale nanostructure of sputter-deposited columnar Zr0.7Ta0.3B1.5 thin films. The columns, 95 ± 17 Å, are core/shell nanostructures in which 80 ± 15-Å cores are crystalline hexagonal-AlB2-structure Zr-rich stoichiometric Zr1−xTaxB2. The shell structure is a narrow dense, disordered region that is Ta-rich and highly B-deficient. The cores are formed under intense ion mixing via preferential Ta segregation, due to the lower formation enthalpy of TaB2 than ZrB2, in response to the chemical driving force to form a stoichiometric compound. The films with unique combination of nanosized crystalline cores and dense metallic-glass-like shells provide excellent mechanical properties.

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  • 7.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Thörnberg, Jimmy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci & Technol, Taiwan.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci & Technol, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Improving the high-temperature oxidation resistance of TiB2 thin films by alloying with Al2020In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 196, p. 677-689Article in journal (Refereed)
    Abstract [en]

    Refractory transition-metal diborides (TMB2) are candidates for extreme environments due to melting points above 3000 degrees C, excellent hardness, good chemical stability, and thermal and electrical conductivity. However, they typically suffer from rapid high-temperature oxidation. Here, we study the effect of Al addition on the oxidation properties of sputter-deposited TiB2-rich Ti1-xAlxBy thin films and demonstrate that alloying the films with Al significantly increases the oxidation resistance with a slight decrease in hardness. TiB2.4 layers are deposited by dc magnetron sputtering (DCMS) from a TiB2 target, while Ti1-xAlxBy alloy films are grown by hybrid high-power impulse and dc magnetron co-sputtering (Al-HiPIMS/TiB2-DCMS). All as-deposited films exhibit columnar structure. The column boundaries of TiB2.4 are B-rich, while Ti0.68Al0.32B1.35 alloys have Ti-rich columns surrounded by a Ti(1-x)Al(x)By tissue phase which is predominantly Al rich. Air-annealing TiB2.4 at temperatures above 500 degrees C leads to the formation of oxide scales that do not contain B and mostly consist of a rutile-TiO2 (s) phase. The resulting oxidation products are highly porous due to the evaporation of B2O3 (g) phase as well as the coarsening of TiO2 crystallites. This poor oxidation resistance is significantly improved by alloying with Al. While air-annealing at 800 degrees C for 0.5 h results in the formation of an similar to 1900-nm oxide scale on TiB2.4, the thickness of the scale formed on the Ti0.68Al0.32B1.35 alloys is similar to 470 nm. The enhanced oxidation resistance is attributed to the formation of a dense, protective Al-containing oxide scale that considerably decreases the oxygen diffusion rate by suppressing the oxide-crystallites coarsening. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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  • 8.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Wu, Zhengtao
    School of Electromechanical Engineering, Guangdong University of Technology, China.
    Sortica, Mauritio A.
    Applied Nuclear Physics, Department of Physics and Astronomy, Uppsala University, Sweden.
    Primetzhofer, Daniel
    Applied Nuclear Physics, Department of Physics and Astronomy, Uppsala University, Sweden.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taiwan.
    Greene, Joseph E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Research Laboratory and Department of Materials Science, University of Illinois, USA; Department of Materials Science and Engineering, National Taiwan University of Science and Technology, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Age hardening in superhard ZrB2-rich Zr1-xTaxBy thin films2021In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 191, p. 120-125Article in journal (Refereed)
    Abstract [en]

    We recently showed that sputter-deposited Zr1-xTaxBy thin films have hexagonal AlB2-type columnar nanostructure in which column boundaries are B-rich for x < 0.2, while Ta-rich for x ≥ 0.2. As-deposited layers with x ≥ 0.2 exhibit higher hardness and, simultaneously, enhanced toughness. Here, we study the mechanical properties of ZrB2.4, Zr0.8Ta0.2B1.8, and Zr0.7Ta0.3B1.5 films annealed in Ar atmosphere as a function of annealing temperature Ta up to 1200 °C. In-situ and ex-situ nanoindentation analyses reveal that all films undergo age hardening up to Ta = 800 °C, with the highest hardness achieved for Zr0.8Ta0.2B1.8 (45.5±1.0 GPa). The age hardening, which occurs without any phase separation or decomposition, can be explained by point-defect recovery that enhances chemical bond density. Although hardness decreases at Ta > 800 °C due mainly to recrystallization, column coarsening, and planar defect annihilation, all layers show hardness values above 34 GPa over the entire Ta range.

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  • 9.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Controlling the B/Ti ratio of TiBx thin films grown by high-power impulse magnetron sputtering2018In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 36, no 3, article id 030604Article in journal (Refereed)
    Abstract [en]

    TiBx thin films grown from compound TiB2 targets by magnetron sputter deposition are typically highly over-stoichiometric, with x ranging from 3.5 to 2.4, due to differences in Ti and B preferential-ejection angles and gas-phase scattering during transport from the target to the substrate. Here, the authors demonstrate that stoichiometric TiB2 films can be obtained using highpower impulse magnetron sputtering (HiPIMS) operated in power-controlled mode. The B/Ti ratio x of films sputter-deposited in Ar is controllably varied from 2.08 to 1.83 by adjusting the length of HiPIMS pulses t(on) between 100 and 30 mu s, while maintaining average power and pulse frequency constant. This results in peak current densities J(T), peak ranging from 0.27 to 0.88 A/cm(2). Energy- and time-resolved mass spectrometry analyses of the ion fluxes incident at the substrate position show that the density of metal ions increases with decreasing t(on) due to a dramatic increase in J(T, peak) resulting in the strong gas rarefaction. With t(on)amp;lt;60 mu s (J(T),(peak)amp;gt; 0.4 A/cm(2)), film growth is increasingly controlled by ions incident at the substrate, rather than neutrals, as a result of the higher plasma dencity and, hence, electron-impact ionization probablity. Thus, since sputter- ejected Ti atoms have a higher probability of being ionized than B atoms, due to their lower first-ionization potential and larger ionization cross-section, the Ti concentration in as-deposited films increases with decreasing ton (increasing J(T,peak)) as ionized sputtered species are steered to the substrate by the plasma in order to maintain charge neutrality. Published by the AVS.

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  • 10.
    Bakhit, Babak
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Primetzhofer, Daniel
    Uppsala University, Sweden.
    Pitthan, Eduardo
    Uppsala University, Sweden.
    Sortica, Mauricio A.
    Uppsala University, Sweden.
    Ntemou, Eleni
    Uppsala University, Sweden.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, USA; National Taiwan University of Science and Technology, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Systematic compositional analysis of sputter-deposited boron-containing thin films2021In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 39, no 6, article id 063408Article in journal (Refereed)
    Abstract [en]

    Boron-containing materials exhibit a unique combination of ceramic and metallic properties that are sensitively dependent on their given chemical bonding and elemental compositions. However, determining the composition, let alone bonding, with sufficient accuracy is cumbersome with respect to boron, being a light element that bonds in various coordinations. Here, we report on the comprehensive compositional analysis of transition-metal diboride (TMBx) thin films (TM = Ti, Zr, and Hf) by energy-dispersive x-ray spectroscopy (EDX), x-ray photoelectron spectroscopy (XPS), time-of-flight elastic recoil detection analysis (ToF-ERDA), Rutherford backscattering spectrometry (RBS), and nuclear reaction analysis (NRA). The films are grown on Si and C substrates by dc magnetron sputtering from stoichiometric TMB2 targets and have hexagonal AlB2-type columnar structures. EDX considerably overestimates B/TM ratios, x, compared to the other techniques, particularly for ZrBx. The B concentrations obtained by XPS strongly depend on the energy of Ar+ ions used for removing surface oxides and contaminants prior to analyses and are more reliable for 0.5 keV Ar+. ToF-ERDA, RBS, and NRA yield consistent compositions in TiBx. They also prove TiBx and ZrBx films to be homogeneous with comparable B/TM ratios for each film. However, ToF-ERDA, employing a 36-MeV 127I8+ beam, exhibits challenges in depth resolution and quantification of HfBx due to plural and multiple scattering and associated energy loss straggling effects. Compared to ToF-ERDA, RBS (for the film grown on C substrates) and NRA provide more reliable B/Hf ratios. Overall, a combination of methods is recommended for accurately pinpointing the compositions of borides that contain heavy transition metals.

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  • 11.
    Chipatecua Godoy, Yuri
    et al.
    CINVESTAV, Mexico.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Olaya Florez, Jairo
    Univ Nacl Colombia, Colombia.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Bustos, Erika
    CIDETEQ, Mexico.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Herrera-Gomez, Alberto
    CINVESTAV, Mexico.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Corrosion Resistant TiTaN and TiTaAlN Thin Films Grown by Hybrid HiPIMS/DCMS Using Synchronized Pulsed Substrate Bias with No External Substrate Heating2019In: Coatings, ISSN 2079-6412, COATINGS, Vol. 9, no 12, article id 841Article in journal (Refereed)
    Abstract [en]

    Ti0.92Ta0.08N and Ti0.41Al0.51Ta0.08N thin films grown on stainless-steel substrates, with no external heating, by hybrid high-power impulse and dc magnetron sputtering (HiPIMS/DCMS), were investigated for corrosion resistance. The Ta target was operated in HiPIMS mode to supply pulsed Ta-ion fluxes, while two Ti (or Ti and Al) targets were operated in DCSM mode in order to provide a high deposition rate. Corrosion resistance was investigated using potentiodynamic polarization and electrochemical impedance spectroscopy employing a 3.5% NaCl solution at room temperature. The 300-nm-thick transition-metal nitride coatings exhibited good corrosion resistance due to film densification resulting from pulsed heavy Ta-ion irradiation during film growth. Corrosion protective efficiencies were above 99.8% for both Ti0.41Al0.51Ta0.08N and Ti0.92Ta0.08N, and pore resistance was apparently four orders of magnitude higher than for bare 304 stainless-steel substrates.

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  • 12.
    Dorri, Megan
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Thörnberg, Jimmy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hellgren, Niklas
    Messiah Univ, PA 17055 USA.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petruhins, Andrejs
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Klimashin, Fedor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci & Technol, Taiwan.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Synthesis and characterization of CrB 2 thin films grown by DC magnetron sputtering2021In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 200, article id 113915Article in journal (Refereed)
    Abstract [en]

    CrB x thin films with 1.90 &lt; x &lt; 2.08 have been deposited by direct-current magnetron sputtering (DCMS) from a stoichiometric CrB 2 target at 5 and 20 mTorr (0.67 and 2.67 Pa) Ar pressure onto sapphire (0 0 01) substrates. All films, irrespective of deposition conditions, exhibit a (0 0 01) texture. Attesting to the achievement of close-to-stoichiometric composition, epitaxial film growth is observed at 900 ?C, while film growth at 500 ?C yields (0001) fiber texture. Film composition does not depend on substrate temperature but exhibits slightly reduced B content with increasing pressure for samples deposited at 900 ?C. Excess B in the overstoichiometric epitaxial CrB 2.08 films segregates to form B-rich inclusions. Understoichiometry in CrB 1.90 films is accommodated by Cr-rich stacking faults on { 1 1? 00 } prismatic planes. ? 2021 The Author(s). Published by Elsevier Ltd on behalf of Acta Materialia Inc. This is an open access article under the CC BY license ( http://creativecommons.org/licenses/by/4.0/ )

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  • 13.
    Dorri, Samira
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois at Urbana-Champaign, USA; National Taiwan University of Science and Technology, Taiwan.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Oxidation kinetics of overstoichiometric TiB2 thin films grown by DC magnetron sputtering2022In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 206, article id 110493Article in journal (Refereed)
    Abstract [en]

    We systematically study the oxidation properties of sputter-deposited TiB2.5 coatings up to 700 °C. Oxide-scale thickness dox increases linearly with time ta for 300, 400, 500, and 700 °C, while an oxidation-protective behavior occurs with dox=250∙ta0.2 at 600 °C. Oxide-layer’s structure changes from amorphous to rutile/anatase-TiO2 at temperatures ≥ 500 °C. Abnormally low oxidation rate at 600 °C is attributed to a highly dense columnar TiO2-sublayer growing near oxide/film interface with a top-amorphous thin layer, suppressing oxygen diffusion. A model is proposed to explain the oxide-scale evolution at 600 °C. Decreasing heating rate to 1.0 °C/min plays a noticeable role in the TiB2.5 oxidation.

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  • 14.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Orebro Univ, Sweden.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr Univ Bochum, Germany.
    Landälv, Ludvig
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Sandvik Coromant AB, Sweden.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mechanical properties of VMoNO as a function of oxygen concentration: Toward development of hard and tough refractory oxynitrides2019In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 6, article id 061508Article in journal (Refereed)
    Abstract [en]

    Improved toughness is a central goal in the development of wear-resistant refractory ceramic coatings. Extensive theoretical and experimental research has revealed that NaCl-structure VMoN alloys exhibit surprisingly high ductility combined with high hardness and toughness. However, during operation, protective coatings inevitably oxidize, a problem that may compromise material properties and performance. Here, the authors explore the role of oxidation in altering VMoN properties. Density functional theory and theoretical intrinsic hardness models are used to investigate the mechanical behavior of cubic V0.5Mo0.5N1-xOx solid solutions as a function of the oxygen concentration x. Elastic constant and intrinsic hardness calculations show that oxidation does not degrade the mechanical properties of V0.5Mo0.5N. Electronic structure analyses indicate that the presence of oxygen reduces the covalent bond character, which slightly lowers the alloy strength and intrinsic hardness. Nevertheless, the character of metallic d-d states, which are crucial for allowing plastic deformation and enhancing toughness, remains unaffected. Overall, the authors results suggest that VMoNO oxynitrides, with oxygen concentrations as high as 50%, possess high intrinsic hardness, while still being ductile. Published by the AVS.

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  • 15.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Ti and N adatom descent pathways to the terrace from atop two-dimensional TiN/TiN(001) islands2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 558, p. 37-46Article in journal (Refereed)
    Abstract [en]

    We use classical molecular dynamics and the modified embedded atom method to determine residence times and descent pathways of Ti and N adatoms on square, single-atom-high, TiN islands on TiN(001). Simulations are carried out at 1000 K, which is within the optimal range for TiN(001) epitaxial growth. Results show that the frequency of descent events, and overall adatom residence times, depend strongly on both the TiN(001) diffusion barrier for each species as well as the adatom island-edge location immediately prior to descent. Ti adatoms, with a low diffusion barrier, rapidly move toward the island periphery, via funneling, where they diffuse along upper island edges. The primary descent mechanism for Ti adatoms is via push-out/exchange with Ti island-edge atoms, a process in which the adatom replaces an island edge atom by moving down while pushing the edge atom out onto the terrace to occupy an epitaxial position along the island edge. Double push-out events are also observed for Ti adatoms descending at N corner positions. N adatoms, with a considerably higher diffusion barrier on TiN(001), require much longer times to reach island edges and, consequently, have significantly longer residence times. N adatoms are found to descend onto the terrace by direct hopping over island edges and corner atoms, as well as by concerted push-out/exchange with N atoms adjacent to Ti corners. For both adspecies, we also observe several complex adatom/island interactions, before and after descent onto the terrace, including two instances of Ti islandatom ascent onto the island surface.

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    Ti and N adatom descent pathways to the terrace from atop two-dimensional TiN/TiN(001) islands
  • 16.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    The dynamics of TiNx (x = 1 – 3) admolecule interlayer and intralayer transport on TiN/TiN(001) islands2015In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 589, p. 133-144Article in journal (Refereed)
    Abstract [en]

    It has been shown both experimentally and by density functional theory calculations that the primary diffusing species during the epitaxial growth of TiN/TiN(001) are Ti and N adatoms together with TiNx complexes (x = 1, 2, 3), in which the dominant N-containing admolecule species depends upon the incident N/Ti flux ratio. Here, we employ classical molecular dynamics (CMD) simulations to probe the dynamics of TiNx (x = 1–3) admolecules on 8 × 8 atom square, single-atom-high TiN islands on TiN(001), as well as pathways for descent over island edges. The simulations are carried out at 1000 K, a reasonable epitaxial growth temperature. We find that despite their lower mobility on infinite TiN(001) terraces, both TiN and TiN2 admolecules funnel toward descending steps and are incorporated into island edges more rapidly than Ti adatoms. On islands, TiN diffuses primarily via concerted translations, but rotation is the preferred diffusion mechanism on infinite terraces. TiN2 migration is initiated primarily by rotation about one of the N admolecule atoms anchored at an epitaxial site. TiN admolecules descend from islands by direct hopping over edges and by edge exchange reactions, while TiN2 trimers descend exclusively by hopping. In contrast, TiN3 admolecules are essentially stationary and serve as initiators for local island growth. Ti adatoms are the fastest diffusing species on infinite TiN(001) terraces, but on small TiN/TiN(001) islands, TiN dimers provide more efficient mass transport. The overall results reveal the effect of the N/Ti precursor flux ratio on TiN(001) surface morphological evolution and growth modes.

  • 17.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr University of Bochum, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Effects of incident N atom kinetic energy on TiN/TiN(001) film growth dynamics: A molecular dynamics investigation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 2, article id 025302Article in journal (Refereed)
    Abstract [en]

    Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200 K, a temperature within the optimal range for epitaxial TiN growth, with an incident N-to-Ti flux ratio of four, are carried out using incident N energies E-N = 2 and 10 eV and incident Ti energy E-Ti = 2 eV. To further highlight the effect of E-N, we grow a bilayer film with E-N = 2 eV initially and then switch to E-N = 10 eV. As-deposited layers are analyzed as a function of composition, island-size distribution, island-edge orientation, and vacancy formation. Results show that growth with E-N = 2 eV results in films that are globally overstoichiometric with islands bounded by N-terminated polar 110 edges, whereas films grown with E-N = 10 eV are flatter and closer to stoichiometric. However, E-N = 10 eV layers exhibit local N deficiency leading to the formation of isolated 111-oriented islands. Films grown by changing the incident energy from 2 to 10 eV during growth are more compact than those grown entirely with E-N = 2 eV and exhibit greatly reduced concentrations of upper-layer adatoms, admolecules, and small clusters. Islands with 110 edges formed during growth with E-N = 2 eV transform to islands with 100 edges as E-N is switched to 10 eV. Published by AIP Publishing.

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  • 18.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr Univ Bochum, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Elastic properties and plastic deformation of TiC- and VC-based alloys2018In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 144, p. 376-385Article in journal (Refereed)
    Abstract [en]

    Transition-metal (TM) carbides are an important class of hard, protective coating materials; however, their brittleness often limits potential applications. We use density functional theory to investigate the possibility of improving ductility by forming pseudobinary cubic (MMC)-M-1-C-2 alloys, for which M-1 = Ti or V and M-2 = W or Mo. The alloying elements are chosen based on previous results showing improved ductility of the corresponding pseudobinary nitride alloys with respect to their parent compounds. While commonly-used empirical criteria do not indicate enhanced ductility in the carbide alloys, calculated stress/strain curves along known slip systems, supported by electronic structure analyses, indicate ductile behavior for VMoC. As VMoC layers are sheared along the 1 (1) over bar0 direction on {111} planes, the stress initially increases linearly up to a yield point where the accumulated stress is partially dissipated. With further increase in strain, the stress increases again until fracture occurs. A similar mechanical behavior is observed for the corresponding TM nitride VMoN, known to be a ductile ceramic material [1]. Thus, our results show that VMoC is a TM carbide alloy which may be both hard and ductile, i.e. tough. (C) 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

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  • 19.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth2016In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 34, no 4, p. 041509-1-041509-9Article in journal (Refereed)
    Abstract [en]

    Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200K are carried out using incident flux ratios N/Ti -1, 2, and 4. The films are analyzed as a function of composition, island size distribution, island edge orientation, and vacancy formation. Results show that N/Ti-1 films are globally understoichiometric with dispersed Ti-rich surface regions which serve as traps to nucleate 111-oriented islands, leading to local epitaxial breakdown. Films grown with N/Ti=2 are approximately stoichiometric and the growth mode is closer to layer-by-layer, while N/Ti-4 films are stoichiometric with N-rich surfaces. As N/Ti is increased from 1 to 4, island edges are increasingly polar, i. e., 110-oriented, and N-terminated to accommodate the excess N flux, some of which is lost by reflection of incident N atoms. N vacancies are produced in the surface layer during film deposition with N/Ti-1 due to the formation and subsequent desorption of N-2 molecules composed of a N adatom and a N surface atom, as well as itinerant Ti adatoms pulling up N surface atoms. The N vacancy concentration is significantly reduced as N/Ti is increased to 2; with N/Ti-4, Ti vacancies dominate. Overall, our results show that an insufficient N/Ti ratio leads to surface roughening via nucleation of small dispersed 111 islands, whereas high N/Ti ratios result in surface roughening due to more rapid upper-layer nucleation and mound formation. The growth mode of N/Ti-2 films, which have smoother surfaces, is closer to layer-by-layer. (C) 2016 American Vacuum Society.

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  • 20.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Orebro Univ, Sweden.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr Univ Bochum, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    TiN film growth on misoriented TiN grains with simultaneous low-energy bombardment: Restructuring leading to epitaxy2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 688, article id 137380Article in journal (Refereed)
    Abstract [en]

    We perform large-scale molecular dynamics simulations of TiN deposition at 1200 K on TiN substrates consisting of under-stoichiometric (N/Ti = 0.86) misoriented grains. The energy of incoming Ti atoms is 2 eV and that of incoming N atoms is 10 eV. The simulations show that misoriented grains are reoriented during the early stages of growth, after which the film grows 001 epitaxially and is nearly stoichiometric. The grain reorientation coincides with an increase in film N/Ti ratio. As the grains reorient, additional nitrogen can no longer be accommodated, and the film composition becomes stoichiometric as the overlayer grows epitaxially.

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  • 21.
    Eriksson, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Si incorporation in Ti1-xSixN films grown on TiN(001) and (001)-faceted TiN(111) columns2014In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 257, p. 121-128Article in journal (Refereed)
    Abstract [en]

    Thin films consisting of TiN nanocrystallites encapsulated in a fully percolated SiNy tissue phase are archetypes for hard and superhard nanocomposites. Here, we investigate metastable SiNy solid solubility in TiN and probe the effects of surface segregation during the growth of TiSiN films onto substrates that are either flat TiN(001)/MgO(001) epitaxial buffer layers or TiN(001) facets of length 1-5 nm terminating epitaxial TiN(111) nanocolumns, separated by voids, deposited on epitaxial TiN(111)/MgO(111) buffer layers. Using reactive magnetron sputter deposition, the TiSiN layers were grown at 550 degrees C and the TiN buffer layers at 900 degrees C On TiN(001), the films are NaCl-structure single-phase metastable Ti1-xSixN(001) with N/(Ti + Si) = 1 and 0 less than= x less than= 0.19. These alloys remain single-crystalline to critical thicknesses h(c) ranging from 100 +/- 30 nm with x = 0.13 to 40 +/- 10 nm with x = 0.19. At thicknesses h greater than h(c), the epitaxial growth front breaks down locally to form V-shaped polycrystalline columns with an underdense feather-like nanostructure. In contrast, the voided epitaxial TiN(111) columnar surfaces, as well as the TiN(001) facets, act as sinks for SiNy. For Ti1-xSixN layers with global average composition values less than x greater than = 0.16, the local x value in the middle of Ti1-xSixN columns increases from 0.08 for columns with radius r similar or equal to 2 nm to x = 0.14 with r similar or equal to 4 nm. The average out-of-plane lattice parameter of epitaxial nanocolumns encapsulated in SiNy decreases monotonically with increasing Si fraction less than x greater than, indicating the formation of metastable (Ti,Si)N solid solutions under growth conditions similar to those of superhard nanocomposites for which the faceted surfaces of nanograins also provide sinks for SiNy.

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  • 22.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Andersson, J. M.
    Seco Tools AB, SE-737 82 Fagersta, Sweden.
    Mei, A.R.B.
    Frederick Seitz Materials Research Laboratory and Materials Science Department, University of Illinois, USA.
    Howe, B.M.
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, Ohio, USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Growth and Properties of Amorphous Hf1−x−yAlxSiyN (0≤x≤0.2; 0≤y≤0.2) and a-Hf0.6Al0.2Si0.2N/nc-HfN Multilayers by DC Reactive Magnetron Sputtering from a Single Hf0.60Al0.20Si0.20 TargetManuscript (preprint) (Other academic)
    Abstract [en]

    Amorphous (a) and nanocrystalline (nc) Hf1−x−yAlxSiyN and multilayer a-Hf0.6Al0.2Si0.2N/nc-HfN films are grown on Si(001) at temperatures Ts = 100-450 ◦C using ultrahigh vacuum magnetically-unbalanced reactive magnetron sputtering from a single Hf0.60Al0.20Si0.20 target in a 5%-N2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1−x−yAlxSiyN is controlled during growth by independently varying the ion energy (Ei) and the ion-to-metal flux ratio (Ji/JMe) incident at the film surface. With Ji/JMe = 8, the composition and nanostructure of the films ranges from x-ray amorphous with 1-x-y = 0.60 at Ei = 15 eV, to an amorphous matrix with encapsulated nanocrystals with 1-x-y = 0.66-0.84 at Ei = 25-35 eV, to nanocrystalline with 1-x-y = 0.96-1.00 at Ei = 45-65 eV. Varying Ji/JMe with Ei = 13 eV yields amorphous alloy films at Ts = 100 ◦C. a-Hf0.6Al0.6Si0.6N/nc-HfN multilayers with periods Λ = 2-20 nm exhibit enhanced fracture toughness compared to polycrystalline VN, TiN, and Ti0.5Al0.5N reference samples; multilayer hardness values increase monotonically from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm.

  • 23.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Howe, B.M.
    Air Force Research Laboratory, Materials and Manufacturing Directorate, Wright-Patterson AFB, Ohio, USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mei, A. R. B.
    Frederick Seitz Materials Research Laboratory and Materials Science Department, University of Illinois, USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, J.E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hf-Al-Si-N multilayers deposited by reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target using high-flux, low-energy modulated substrate bias: film growth and properties2014Manuscript (preprint) (Other academic)
    Abstract [en]

    Hf1−x−yAlxSiyN (0≤x≤0.14, 0≤y≤0.13) single layers and multilayer films are grown on Si(001) at a substrate temperature Ts=250 °C using ultrahigh vacuum magnetically-unbalanced reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target in a 5%-N2/Ar atmosphere at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1−x−yAlxSiyN is controlled during growth by varying the ion energy (Ei) of the ions incident at the film surface, keeping the ion-to-metal flux ratio (Ji/JMe) constant at 8. By sequentially switching Ei between 10 and 40 eV, Hf0.77Al0.10Si0.13N/Hf0.78Al0.14Si0.08N multilayers with bilayer periods Λ = 2-20 nm are grown, in which the Si2p bonding state changes from predominantly Si-Si bonds for films grown at Ei = 10 eV, to mainly Si-N bonds at Ei = 40 eV. Multilayer hardness values increase monotonically from 20 GPa with Λ = 20 nm to 27 GPa with Λ = 2 nm, while multilayer fracture toughness increases with increasing Λ. Multilayers with Λ = 10 nm have the optimized property combination of being bothrelatively hard, H∼24 GPa, and fracture tough.

  • 24.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Howe, Brandon M.
    US Air Force, OH 45433 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mei, A. B.
    University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film2015In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 33, no 5, p. 05E103-1-05E103-9Article in journal (Refereed)
    Abstract [en]

    Hf1-x-yAlxSiyN (0 less than= x less than= 0.14, 0 less than= y less than= 0.12) single layer and multilayer films are grown on Si(001) at 250 degrees C using ultrahigh vacuum magnetically unbalanced reactive magnetron sputtering from a single Hf0.6Al0.2Si0.2 target in mixed 5%-N-2/Ar atmospheres at a total pressure of 20 mTorr (2.67 Pa). The composition and nanostructure of Hf1-x-yAlxSiyN films are controlled by varying the energy Ei of the ions incident at the film growth surface while maintaining the ion-to-metal flux ratio constant at eight. Switching E-i between 10 and 40 eV allows the growth of Hf0.78Al0.10Si0.12N/Hf0.78Al0.14Si0.08N multilayers with similar layer compositions, but in which the Si bonding state changes from predominantly Si-Si/Si-Hf for films grown with E-i = 10 eV, to primarily Si-N with E-i = 40 eV. Multilayer hardness values, which vary inversely with bilayer period Lambda, range from 20 GPa with Lambda = 20 nm to 27 GPa with Lambda = 2 nm, while fracture toughness increases directly with Lambda. Multilayers with Lambda = 10nm combine relatively high hardness, H similar to 24GPa, with good fracture toughness. (C) 2015 American Vacuum Society.

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  • 25.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bolz, S.
    CemeCon AG, Germany.
    Mesic, B.
    CemeCon AG, Germany.
    Koelker, W.
    CemeCon AG, Germany.
    Schiffers, Ch.
    CemeCon AG, Germany.
    Lemmer, O.
    CemeCon AG, Germany.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Low-temperature growth of dense and hard Ti0.41Al0.51Ta0.08N films via hybrid HIPIMS/DC magnetron co-sputtering with synchronized metal-ion irradiation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171902Article in journal (Refereed)
    Abstract [en]

    Hard Ti1-xAlxN thin films are of importance for metal-cutting applications. The hardness, thermal stability, and oxidation resistance of these coatings can be further enhanced by alloying with TaN. We use a hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) technique to grow dense and hard Ti0.41Al0.51Ta0.08N alloys without external heating (T-s amp;lt; 150 degrees C). Separate Ti and Al targets operating in the DCMS mode maintain a deposition rate of similar to 50 nm/min, while irradiation of the growing film by heavy Ta+/Ta2+ ions from the HIPIMS-powered Ta target, using dc bias synchronized to the metal-ion-rich part of each HIPIMS pulse, provides effective near-surface atomic mixing resulting in densification. The substrate is maintained at floating potential between the short bias pulses to minimize Ar+ bombardment, which typically leads to high compressive stress. Transmission and scanning electron microscopy analyses reveal dramatic differences in the microstructure of the co-sputtered HIPIMS/DCMS films (Ta-HIPIMS) compared to films with the same composition grown at floating potential with all targets in the DCMS mode (Ta-DCMS). The Ta-DCMS alloy films are only similar to 70% dense due to both inter-and intra-columnar porosity. In contrast, the Ta-HIPIMS layers exhibit no inter-columnar porosity and are essentially fully dense. The mechanical properties of Ta-HIPIMS films are significantly improved with hardness and elastic modulus values of 28.0 and 328 GPa compared to 15.3 and 289 GPa for reference Ta-DCMS films. Published by AIP Publishing.

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  • 26.
    Gangaprasad Rao, Smita
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Illgner, Pascal Manuel
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Nagy, Gyula
    Uppsala Univ, Sweden.
    Djemia, Philippe
    Univ Sorbonne Paris Nord, France.
    Primetzhofer, Daniel
    Uppsala Univ, Sweden.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Le Febvrier, Arnaud
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eklund, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Low temperature epitaxial growth of Cantor-nitride thin films by magnetic field assisted magnetron sputtering2023In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 41, no 5, article id 053415Article in journal (Refereed)
    Abstract [en]

    Low-temperature epitaxial growth of multicomponent alloy-based thin films remains an outstanding challenge in materials science and is important for established fundamental properties of these complex materials. Here, Cantor nitride (CrMnFeCoNi)N thin films were epitaxially grown on MgO(100) substrates at low deposition temperature by magnetic-field-assisted dc-magnetron sputtering, a technique where a magnetic field is applied to steer the dense plasma to the substrate thereby influencing the flux of Ar-ions bombarding the film during growth. Without ion bombardment, the film displayed textured growth. As the ion flux was increased, the films exhibited epitaxial growth. The epitaxial relationship between film and substrate was found to be cube on cube (001)film parallel to(001)MgO, [100]film parallel to[100]MgO. The epitaxy was retained up to a thickness of approximately similar to 100 nm after which the growth becomes textured with a 002 out-of-plane orientation. The elastic constants determined by Brillouin inelastic light scattering were found to be C-11 = 320 GPa, C-12 = 125 GPa, and C-44 = 66 GPa, from which the polycrystalline Youngs modulus was calculated as 204 GPa and Poissons ratio = 0.32, whereas available elastic properties still remained very scarce. (c) 2023 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

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  • 27.
    Ghafoor, Naureen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Johnson, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Klenov, Dmitri
    FEI Company, Eindhoven, The Netherlands.
    Demeulemeester, Jelly
    École Polytechnique de Montréal, Canada.
    Desjardins, Patrick
    École Polytechnique de Montréal, Canada.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Nanolabyrinthine ZrAlN thin films by self-organization of interwoven single-crystal cubic and hexagonal phases2013In: APL Materials, E-ISSN 2166-532X, Vol. 1, no 2, p. 022105-1-022105-6Article in journal (Refereed)
    Abstract [en]

    Self-organization on the nanometer scale is a trend in materials research. Thermodynamic driving forces may, for example, yield chessboard patterns in metal alloys[Y. Ni and A. G. Khachaturyan, Nature Mater. 8, 410–414 (2009)] or nitrides [P. H.Mayrhofer, A. Horling, L. Karlsson, J. Sj ¨ ol¨ en, T. Larsson, and C. Mitterer, Appl. ´Phys. Lett. 83, 2049 (2003)] during spinodal decomposition. Here, we explore theZrN-AlN system, which has one of the largest positive enthalpies of mixing amongthe transition metal aluminum nitrides [D. Holec, R. Rachbauer, L. Chen, L. Wang,D. Luefa, and P. H. Mayrhofer, Surf. Coat. Technol. 206, 1698–1704 (2011); B.Alling, A. Karimi, and I. Abrikosov, Surf. Coat. Technol. 203, 883–886 (2008)].Surprisingly, a highly regular superhard (36 GPa) two-dimensional nanolabyrinthinestructure of two intergrown single crystal phases evolves during magnetron sputter thin film synthesis of Zr0.64Al0.36N/MgO(001). The self-organization is surfacedriven and the synergistic result of kinetic limitations, where the enthalpy reductionbalances both investments in interfacial and elastic energies.

  • 28.
    Ghafoor, Naureen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Holec, D.
    Univ Leoben, Austria.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Self-structuring in Zr1-xAlxN films as a function of composition and growth temperature2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 16327Article in journal (Refereed)
    Abstract [en]

    Nanostructure formation via surface-diffusion-mediated segregation of ZrN and AIN in Zr1-xAlxN films during high mobility growth conditions is investigated for 0 amp;lt;= x amp;lt;= 1. The large immiscibility combined with interfacial surface and strain energy balance resulted in a hard nanolabyrinthine lamellar structure with well-defined (semi) coherent c-ZrN and w-AlN domains of sub-nm to similar to 4 nm in 0.2 amp;lt;= x amp;lt;= 0.4 films, as controlled by atom mobility. For high AlN contents (x amp;gt; 0.49) Al-rich ZrN domains attain wurtzite structure within fine equiaxed nanocomposite wurtzite lattice. Slow diffusion in wurtzite films points towards crystal structure dependent driving force for decomposition. The findings of unlikelihood of isostructural decomposition in c-Zr1-xAlxN, and stability of w-Zr1-xAlxN (in large x films) is complemented with first principles calculations.

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  • 29.
    Ghafoor, Naureen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Klenov, Dmitri O.
    FEI Co, Netherlands.
    Freitag, Bert
    FEI Co, Netherlands.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Self-organized anisotropic (Zr1-xSix)N-y nanocomposites grown by reactive sputter deposition2015In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 82, p. 179-189Article in journal (Refereed)
    Abstract [en]

    The physical properties of hard and superhard nanocomposite thin films are strongly dependent on their nanostructure. Here, we present the results of an investigation of nanostructural evolution and the resulting mechanical properties of (Zr1-xSix)N-y films, with 0 less than= x less than= 1 and 1 less than= y less than= 1.27, grown on MgO(0 0 1) and Al2O3(0 0 0 1) substrates at temperatures T-s = 500-900 degrees C by reactive magnetron sputter deposition from Zr and Si targets. X-ray diffraction and transmission electron microscopy (TEM) results show that there is a T-s/composition window in which stoichiometric Zr-Si-N and amorphous a-Si3N4 phases mutually segregate and self-organize into encapsulated 3-5 um wide ZrN-rich (Zr1-xSix)N columns which extend along the growth direction with a strong (002) texture. Lattice-resolved scanning TEM and energy-dispersive X-ray spectroscopy reveal that the (Zr1-xSix)N-y nanocolumns are separated by a bilayer tissue phase consisting of a thin crystalline SiNy-rich (Zr1-xSix)N-y layer with an a-Si3N4 overlayer. Incorporation of metastable SiN into NaCl-structure ZrN leads to an enhanced nanoindentation hardness H which is a function of T-s and film composition. For nanocomposites with composition (Zr(0.8)Sio(0.2))N-1.14 (10 at.% Si) H, increases from 26 GPa at 500 degrees C to 37 GPa at 900 degrees C. For comparison, the hardness of epitaxial ZrN/MgO(0 0 1) layers grown at T-s = 800 degrees C is 24 GPa. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  • 30.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Towards lowering energy consumption during magnetron sputtering: Benefits of high-mass metal ion irradiation2023In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 134, no 14, article id 140901Article in journal (Refereed)
    Abstract [en]

    The quest for lowering energy consumption during thin film growth by magnetron sputtering techniques becomes of particular importance in view of sustainable development goals. As large fraction of the process energy is consumed in substrate heating for the purpose of providing high adatom mobility necessary to grow dense films, the most straightforward strategy toward more environment-friendly processing is to find alternatives to thermally activated surface diffusion. One possibility is offered by high mass metal ion irradiation of the growing film surface, which has been recently shown to be very effective in densification of transition metal nitride layers grown with no external heating, such that Zone 2 microstructures of the structure-zone model are obtained in the substrate temperature T-s range otherwise typical for Zone 1 growth. The large mass difference between the incident ion and the atoms constituting the film results in effective creation of low energy recoils, which leads to film densification at low T-s. Due to their high mass, metal ions become incorporated at lattice sites beyond the near-surface region of intense recoil generation leading to further densification, while preventing the buildup of residual stress. The practical implementation of this technique discussed in this Perspective employs heavy metal targets operating in the high-power impulse magnetron sputtering (HiPIMS) mode to provide periodic metal-ion fluxes that are accelerated in the electric field of the substrate to irradiate layers deposited from direct current magnetron sputtering (DCMS) sources. A key feature of this hybrid HiPIMS/DCMS configuration is the substrate bias that is synchronized with heavy metal ion fluxes for selective control of their energy and momentum. As a consequence, the major fraction of process energy is used at sputtering sources and for film densification, rather than for heating of the entire vacuum vessel. Model material systems include TiN and metastable NaCl-structure Ti1-yAlyN films, which are well-known for challenges in stoichiometry and phase stability control, respectively, and are of high relevance for industrial applications. This Perspective provides a comprehensive overview of the novel film growth method. After presenting basic concepts, time-resolved measurements of ion fluxes at the substrate plane, essential for selective control of metal ion energy and momentum, are discussed. The role of metal ion mass, energy, momentum, and concentration is described in more detail. As some applications require substrate rotation for conformal coating, a section is devoted to the related complexity in the implementation of metal-ion-synchronized growth under industrial conditions.

  • 31.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    X-ray photoelectron spectroscopy analyses of the electronic structure of polycrystalline Ti1-xAlxN thin films with 0 < x < 0.962014In: Surface Science Spectra, ISSN 1055-5269, E-ISSN 1520-8575, Vol. 21, p. 35-49Article in journal (Refereed)
    Abstract [en]

    Metastable Ti1-xAlxN (0 <  x <  0.96) alloy thin films are grown by reactive magnetron sputter deposition using a combination of high-power pulsed magnetron (HIPIMS) and dc magnetron sputtering (DCMS). Layers are deposited from elemental Ti and Al targets onto Si(001) substrates at 500 °C. All Ti1 xAlxN film surfaces are analyzed by x-ray photoelectron spectroscopy (XPS) employing monochromatic Al Ka radiation (hn = 1486.6 eV). Prior to spectra acquisition, TiAlN surfaces are sputter-cleaned in-situ with 4 keV Ar+ ions incident at an angle of 70° with respect to the surface normal. XPS results reveal satellite structures on the high binding energy side of the Ti2p, Ti3s, and Ti3p core-level signals. The intensities of the primary Ti features (Ti2p, Ti3s, and Ti3p) decrease with increasing AlN concentration such that the satellite peaks dominate spectra from films with x < 0.67. The density-of-states at the Fermi level also decrease with increasing x indicating that the satellite peaks are due to screening of core holes created by the photoionization event. Film compositions, obtained using XPS sensitivity factors, agree to within ±3% with values determined by time-of-flight elastic recoil detection analyses.

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  • 32.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kindlund, Hanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    University of Illinois, Urbana, Illinois, USA.
    Greene, Joseph E
    University of Illinois, Urbana, Illinois.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sputter-cleaned Epitaxial VxMo(1-x)Ny/MgO(001) Thin Films Analyzed by X-ray Photoelectron Spectroscopy: 2. Single-crystal V0.47Mo0.53N0.922013In: Surface Science Spectra, ISSN 1055-5269, E-ISSN 1520-8575, Vol. 20, p. 74-79Article in journal (Refereed)
    Abstract [en]

    Epitaxial Vx Mo (1-x)Ny thin films grown by ultrahigh vacuum reactive magnetron sputter deposition on MgO(001) substrates are analyzed by x-ray photoelectron spectroscopy (XPS). This contribution presents analytical results for 300-nm-thick single-crystal V0.47 Mo 0.53N0.92/MgO(001) films deposited by reactive cosputtering from V (99.95% purity) and Mo (99.95% purity) targets. Film growth is carried out in a UHV chamber with base pressure 2 × 10−9 Torr at 700 °C in mixed Ar/N2 atmospheres at a total pressure of 5 mTorr, with a N2 partial pressure of 3.2 mTorr; a bias of −30 V is applied to the substrate. Films composition is determined by Rutherford backscattering spectrometry (RBS). XPS measurements employ monochromatic Al K α radiation (hν = 1486.6 eV) to analyze V0.47 Mo 0.53N0.92(001) surfaces sputter-cleaned in-situ with 4 keV Ar+ ions incident at an angle of 70° with respect to the surface normal. XPS results show that the ion-etched sample surfaces have no measurable oxygen or carbon contamination; film composition, obtained using XPS sensitivity factors, is V0.34 Mo 0.66N0.81. All core level peaks, including the nearby Mo 3p3/2 (binding energy of 394.1 eV) and N 1s (at 397.5 eV) peaks, are well-resolved. Comparison to the V0.48 Mo 0.52N0.64 single-crystal film, submitted separately to Surface Science Spectra, indicates that with decreasing growth temperature from 900 to 700 °C (and increasing nitrogen concentration in Vx Mo (1-x)Ny from y = 0.64 to 0.81) the N 1s core level peak shifts towards lower binding energy by 0.1 eV while all metal atom peaks move in the opposite direction by the same amount.

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  • 33.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kindlund, Hanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    University of Illinois, Materials Science Department and Frederick Seitz Materials Research.
    Greene, Joseph E
    University of Illinois, Materials Science Department and Frederick Seitz Materials Research.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sputter-cleaned Epitaxial VxMo(1-x)Ny/MgO(001)Thin Films Analyzed by X-ray PhotoelectronSpectroscopy: 3. Polycrystalline V0.49Mo0.51N1.022013In: Surface Science Spectra, ISSN 1055-5269, E-ISSN 1520-8575, Vol. 20, p. 80-85Article in journal (Refereed)
    Abstract [en]

    Vx Mo (1-x)Ny thin films grown by ultrahigh vacuum reactive magnetron sputter deposition on MgO(001) substrates are analyzed by x-ray photoelectron spectroscopy (XPS). This contribution presents analytical results for 300-nm-thick 002-textured polycrystalline V0.49 Mo 0.51N1.02 films deposited by reactive cosputtering from V (99.95 % purity) and Mo (99.95 % purity) targets. Film growth is carried out at 500 °C in mixed Ar/N2 atmospheres at a total pressure of 5 mTorr, with a N2 partial pressure of 3.2 mTorr; a bias of −30 V is applied to the substrate. Films composition is determined by Rutherford backscattering spectrometry (RBS). XPS measurements employ monochromatic Al K α radiation (hν = 1486.6 eV) to analyze V0.49 Mo 0.51N1.02 surface sputter-cleaned in-situ with 4 keV Ar+ ions incident at an angle of 70° with respect to the surface normal. XPS results show that the ion-etched sample surfaces have no measurable oxygen or carbon contamination; film composition, obtained using XPS sensitivity factors, is V0.34 Mo 0.66N1.00. All core level peaks, including the nearby Mo 3p3/2 (binding energy of 394.3 eV) and N 1s (at 397.4 eV) peaks, are well-resolved. Comparison to V0.33 Mo 0.67N0.64 and V0.34 Mo 0.66N0.81 single-crystal film surfaces, submitted separately to Surface Science Spectra, indicates that with decreasing growth temperature from 900 to 700 and 500 °C (and increasing nitrogen concentration in Vx Mo (1-x)Ny from y = 0.64 to 0.81 and 1.00) the N 1s core level peak shifts from 397.6 eV to 397.5 eV to 397.4 eV while metal atom peaks move towards higher binding energy by 0.2-0.4 eV.

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  • 34.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Kindlund, Hanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. Department of Materials Science and the Fredrick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sputter-cleaned Epitaxial VxMo(1-x)Ny/MgO(001)Thin Films Analyzed by X-ray PhotoelectronSpectroscopy: 1. Single-crystal V0.48Mo0.52N0.642013In: Surface Science Spectra, ISSN 1055-5269, E-ISSN 1520-8575, Vol. 20, no 1, p. 68-73Article in journal (Refereed)
    Abstract [en]

    Epitaxial VxMo(1-x)Ny thin films grown by ultrahigh vacuum reactive magnetron sputter deposition on Mg(001) substrates are analyzed by x-ray photoelectron spectroscopy (XPS). This contribution presents analytical results for 300-nm-thick single-crystal V0.48Mo0.52N0.64 films deposited by reactive cosputtering from V (99.95 % purity) and Mo (99.95 % purity) targets. Film growth is carried out at 900 °C in mixed Ar/N2 atmospheres at a total pressure of 5 mTorr, with a N2 partial pressure of 3.2 mTorr; a bias of −30 V is applied to the substrate. Films composition is determined by Rutherford backscattering spectrometry (RBS). XPS measurements employ monochromatic Al K α radiation (hν = 1486.6 eV) to analyze V0.48Mo0.52N0.64(001) surfaces sputter-cleaned in-situ with 4 keV Ar+ ions incident at an angle of 70° with respect to the surface normal. XPS results show that the ion-etched sample surfaces have no measurable oxygen or carbon contamination; film composition, obtained using XPS sensitivity factors, is V0.33Mo0.67N0.64. All core level peaks, including the nearby Mo 3p3/2 (binding energy of 394.0 eV) and N 1s (at 397.6 eV) peaks, are well-resolved.

  • 35.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bolz, Stephan
    CemeCon AG, Wűrselen, Germany.
    Koelker, Werner
    CemeCon AG, Wűrselen, Germany.
    Schiffers, Christoph
    CemeCon AG, Wűrselen, Germany.
    Lemmer, Oliver
    CemeCon AG, Wűrselen, Germany.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA .
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Illinois, Urbana, USA .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Novel strategy for low-temperature, high-rate growth of dense, hard, and stress-free refractory ceramic thin films2014In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 32, no 4, p. 041515-Article in journal (Refereed)
    Abstract [en]

    Growth of fully dense refractory thin films by means of physical vapor deposition (PVD) requires elevated temperatures T-s to ensure sufficient adatom mobilities. Films grown with no external heating are underdense, as demonstrated by the open voids visible in cross-sectional transmission electron microscopy images and by x-ray reflectivity results; thus, the layers exhibit low nanoindentation hardness and elastic modulus values. Ion bombardment of the growing film surface is often used to enhance densification; however, the required ion energies typically extract a steep price in the form of residual rare-gas-ion-induced compressive stress. Here, the authors propose a PVD strategy for the growth of dense, hard, and stress-free refractory thin films at low temperatures; that is, with no external heating. The authors use TiN as a model ceramic materials system and employ hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS and DCMS) in Ar/N-2 mixtures to grow dilute Ti1-xTaxN alloys on Si(001) substrates. The Ta target driven by HIPIMS serves as a pulsed source of energetic Ta+/Ta2+ metal-ions, characterized by in-situ mass and energy spectroscopy, while the Ti target operates in DCMS mode (Ta-HIPIMS/Ti-DCMS) providing a continuous flux of metal atoms to sustain a high deposition rate. Substrate bias V-s is applied in synchronous with the Ta-ion portion of each HIPIMS pulse in order to provide film densification by heavy-ion irradiation (m(Ta) = 180.95 amu versus m(Ti) = 47.88 amu) while minimizing Ar+ bombardment and subsequent trapping in interstitial sites. Since Ta is a film constituent, primarily residing on cation sublattice sites, film stress remains low. Dense Ti0.92Ta0.08N alloy films, 1.8 mu m thick, grown with T-s less than= 120 degrees C (due to plasma heating) and synchronized bias, V-s = 160 V, exhibit nanoindentation hardness H = 25.9 GPa and elastic modulus E = 497 GPa compared to 13.8 and 318 GPa for underdense Ti-HIPIMS/Ti-DCMS TiN reference layers (T-s less than 120 degrees C) grown with the same V-s, and 7.8 and 248 GPa for DCMS TiN films grown with no applied bias (T-s less than 120 degrees C). Ti0.92Ta0.08N residual stress is low, sigma = -0.7 GPa, and essentially equal to that of Ti-HIPIMS/Ti-DCMS TiN films grown with the same substrate bias.

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  • 36.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bolz, S.
    CemeCon AG, Germany .
    Koelker, W.
    CemeCon AG, Germany .
    Schiffers, Ch.
    CemeCon AG, Germany .
    Lemmer, O.
    CemeCon AG, Germany .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Strain-free, single-phase metastable Ti0.38Al0.62N alloys with high hardness: metal-ion energy vs. momentum effects during film growth by hybrid high-power pulsed/dc magnetron cosputtering2014In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 556, p. 87-98Article in journal (Refereed)
    Abstract [en]

    A hybrid deposition process consisting of reactive high-power pulsed and dc magnetron cosputtering (HIPIMS and DCMS) from Ti and Al targets is used to grow Ti1-xAlxN alloys, with x similar to 0.6, on Si(001) at 500 degrees C. Two series of films are deposited in which the energy and momentum of metal ions incident at the growing film are individually varied. In both sets of experiments, a negative bias V-s ranging from 20 to 280 V is applied to the substrate in synchronous, as determined by in-situ mass spectrometry, with the metal-ion-rich part of the HIPIMS pulse. Ion momentum is varied by switching the HIPIMS and dc power supplies to change the mass m and average charge of the primary metal ion. Al-HIPIMS/Ti-DCMS layers grown under Al+ (m(Al) = 26.98 amu) bombardment with 20 less than= V-s less than= 160 V are single-phase NaCl-structure alloys, while films deposited with V-s greater than 160 V are two-phase, cubic plus wurtzite. The corresponding critical average metal-ion momentum transfer per deposited atom for phase separation is less than p(d)*greater than greater than= 135 [eV-amu](1/2). In distinct contrast, layers deposited in the Ti-HIPIMS/Al-DCMS configuration with Ti+/Ti2+ (m(Ti) = 47.88 amu) ion irradiation are two-phase even with the lowest bias, V-s = 20 V, for which less than p(d)*greater than greater than 135 [eV-amu](1/2). Precipitation of wurtzite-structure AlN is primarily determined by the average metal-ion momentum transfer to the growing film, rather than by the deposited metal-ion energy. Ti-HIPIMS/Al-DCMS layers grown with V-s= 20 V are two-phase with compressive stress sigma= -2 GPa which increases to -6.2 GPa at V-s= 120 V; hardness H values range from 17.5 to 27 GPa and are directly correlated with sigma. However, for Al-HIPIMS/Ti-DCMS, the relatively low mass and single charge of the Al+ ion permits tuning properties of metastable cubic Ti0.38Al0.62 N by adjusting V-s to vary, for example, the hardness from 12 to 31 GPa while maintaining sigma similar to 0.

  • 37.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bolz, Stephan
    CemeCon AG, Germany .
    Koelker, Werner
    CemeCon AG, Germany .
    Schiffers, Christoph
    CemeCon AG, Germany .
    Lemmer, Oliver
    CemeCon AG, Germany .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Metal versus rare-gas ion irradiation during Ti1-xAlxN film growth by hybrid high power pulsed magnetron/dc magnetron co-sputtering using synchronized pulsed substrate bias2012In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 30, no 6Article in journal (Refereed)
    Abstract [en]

    Metastable NaCl-structure Ti1-xAlxN is employed as a model system to probe the effects of metal versus rare-gas ion irradiation during film growth using reactive high-power pulsed magnetron sputtering (HIPIMS) of Al and dc magnetron sputtering of Ti. The alloy film composition is chosen to be x = 0.61, near the kinetic solubility limit at the growth temperature of 500 degrees C. Three sets of experiments are carried out: a -60V substrate bias is applied either continuously, in synchronous with the full HIPIMS pulse, or in synchronous only with the metal-rich-plasma portion of the HIPIMS pulse. Alloy films grown under continuous dc bias exhibit a thickness-invariant small-grain, two-phase nanostructure (wurtzite AlN and cubic Ti1-xAlxN) with random orientation, due primarily to intense Ar+ irradiation leading to Ar incorporation (0.2 at. %), high compressive stress (-4.6 GPa), and material loss by resputtering. Synchronizing the bias with the full HIPIMS pulse results in films that exhibit much lower stress levels (-1.8GPa) with no measureable Ar incorporation, larger grains elongated in the growth direction, a very small volume fraction of wurtzite AlN, and random orientation. By synchronizing the bias with the metal-plasma phase of the HIPIMS pulses, energetic Ar+ ion bombardment is greatly reduced in favor of irradiation predominantly by Al+ ions. The resulting films are single phase with a dense competitive columnar structure, strong 111 orientation, no measureable trapped Ar concentration, and even lower stress (-0.9 GPa). Thus, switching from Ar+ to Al+ bombardment, while maintaining the same integrated incident ion/metal ratio, eliminates phase separation, minimizes renucleation during growth, and reduces the high concentration of residual point defects, which give rise to compressive stress.

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  • 38.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Johansson, M
    Seco Tools AB.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Selection of metal ion irradiation for controlling Ti1-xAlxN alloy growth via hybrid HIPIMS/magnetron co-sputtering2012In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 8, p. 1036-1040Article in journal (Refereed)
    Abstract [en]

    We demonstrate, for the first time, the growth of metastable single-phase NaCl-structure high-AlN-content Ti1-xAlxN alloys (x andlt;= 0.64) which simultaneously possess high hardness and low residual stress. The films are grown using a hybrid approach combining high-power pulsed magnetron (HPPMS/HIPIMS) and dc magnetron sputtering of opposing metal targets. With HIPIMS applied to the Al target, Aln+ ion irradiation (dominated by Aln+) of the growing film results in alloys 0.55 andlt;= x andlt;= 0.60 which exhibit hardness H similar to 30 GPa and low stress sigma = 0.2-0.7 GPa, tensile. In sharp contrast, films with corresponding AlN concentrations grown with HIPIMS applied to the Ti target, giving rise to Tin+ ion irradiation (with a significant Ti2+ component), are two-phase - cubic (Ti,Al)N and hexagonal AlN - with low hardness, H = 18-19 GPa, and high compressive stress ranging up to 2.7 GPa. Annealing alloys grown with HIPIMS applied to the Al target results in age hardening due to spinodal decomposition; the hardness of Ti0.41Al0.59N increases from 30 to 33 GPa following a 900 degrees C anneal.

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  • 39.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Johansson, M.P.
    Sweden Seco Tools AB, Sweden .
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Role of Tin+ and Aln+ ion irradiation (n=1, 2) during Ti1-xAlxN alloy film growth in a hybrid HIPIMS/magnetron mode2012In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, no 19-20, p. 4202-4211Article in journal (Refereed)
    Abstract [en]

    Metastable Ti1-xAlxN (0.4 less than= x less than= 0.76) films are grown using a hybrid approach in which high-power pulsed magnetron sputtering (HIPIMS) is combined with dc magnetron sputtering (DCMS). Elemental Al and Ti metal targets are co-sputtered with one operated in HIPIMS mode and the other target in DCMS; the positions of the targets are then switched for the next set of experiments. In both cases, the AlN concentration in the co-sputtered films, deposited at T-s = 500 degrees C with R = 1.5-5.3 angstrom/s, is controlled by adjusting the average DCMS target power. Resulting films are analyzed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, elastic recoil detection analysis, and nanoindentation. Mass spectroscopy is used to determine ion energy distribution functions at the substrate. The distinctly different flux distributions obtained from targets driven in HIPIMS vs. DCMS modes allow the effects of Aln+ and Tin+ (n = 1, 2) ion irradiation on film growth kinetics, and resulting properties, to be investigated separately. Bombardment with Aln+ ions (primarily Al+ in the Al-HIPIMS/Ti-DCMS configuration) during film growth leads to NaCl-structure Ti1-xAlxN (0.53 less than= x less than= 0.60) films which exhibit high hardness (greater than30 GPa) with low stress (0.2-0.7 GPa tensile). In contrast, films with corresponding AlN concentrations grown under Tin+ metal ion irradiation (with a significant Ti2+ component) in the Ti-HIPIMS/Al-DCMS mode have much lower hardness, 18-19 GPa, and high compressive stress ranging up to 2.7 GPa. The surprisingly large variation in mechanical properties results from the fact that the kinetic AlN solubility limit x(max) in Ti1-xAlxN depends strongly on, in addition to T-s and R, the target power configuration during growth and hence the composition of the ion flux. AlN with x(max)similar to 64 mol% can be accommodated in the NaCl structure under Aln+ ion flux, compared with similar to 40 mol% for growth with Tin+ flux. The strong asymmetry in film growth reaction paths is due primarily to the fact that the doubly-ionized metal ion flux is approximately two orders of magnitude higher from the Ti target, than from Al, powered with HIPIMS. This asymmetry becomes decisive upon application of a moderate substrate bias voltage, -60 V, applied synchronously with HIPIMS pulses, during growth.

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  • 40.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science and Physics Departments, Frederick Seitz Materials Research Laboratory, University of of Illinois, Urbana, IL, United States.
    Greene, Joseph E.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science and Physics Departments, Frederick Seitz Materials Research Laboratory, University of of Illinois, Urbana, IL, United States.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity2016In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 122, p. 40-44Article in journal (Refereed)
    Abstract [en]

    We report the first results on nanostructured N-doped bcc-Cr films exhibiting the unique combination of ceramic hardness with metallic toughness and electrical conductivity at unexpectedly low N concentrations, ~ 5 at.%. The Cr:N films are deposited at 200 C in N2/Ar mixtures by high-power pulsed magnetron sputtering using tunable time-domain control of Cr+ and Cr2+ ion fluxes incident at the film growth surface. Subplanted N atoms impede annealing of metal-ion induced point defects and hinder bcc-Cr grain growth, resulting in a material with a nearly isotropic nanostructure and atomically smooth surface, rather than typical Cr:N solid solutions consisting of faceted microcolumns. © 2016 Elsevier Ltd.

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  • 41.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Patscheider, J.
    Empa, Switzerland.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Max Planck Institute Eisenforsch GmbH, Germany.
    Ektarawong, Annop
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Control of Ti1-xSixN nanostructure via tunable metal-ion momentum transfer during HIPIMS/DCMS co-deposition2015In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 280, p. 174-184Article in journal (Refereed)
    Abstract [en]

    Ti1-xSixN (0 less than= x less than= 0.26) thin films are grown in mixed Ar/N-2 discharges using hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS). In the first set of experiments, the Si target is powered in HIPIMS mode and the Ti target in DCMS; the positions of the targets are then switched for the second set. In both cases, the Si concentration in co-sputtered films, deposited at T-s = 500 degrees C, is controlled by adjusting the average DCMS target power. A pulsed substrate bias of -60 V is applied in synchronous with the HIPIMS pulse. Depending on the type of pulsed metal-ion irradiation incident at the growing film, Ti+/Ti2+ vs. Si+/Si2+, completely different nanostructures are obtained. Ti+/Ti2+ irradiation during Ti-HIPIMS/Si-DCMS deposition leads to a phase-segregated nanocolumnar structure with TiN-rich grains encapsulated in a SiNz tissue phase, while Si+/Si2+ ion irradiation in the Si-HIPIMS/Ti-DCMS mode results in the formation of Ti1-xSixN solid solutions with x less than= 024. Film properties, including hardness, modulus of elasticity, and residual stress exhibit a dramatic dependence on the choice of target powered by HIPIMS. Ti-HIPIMS/Si-DCMS TiSiN nanocomposite films are superhard over a composition range of 0.04 less than= x less than= 0.26, which is significantly wider than previously reported. The hardness H of films with 0.13 less than= x less than= 0.26 is similar to 42 GPa; however, the compressive stress is also high, ranging from -6.7 to -8.5 GPa. Si-HIPIMS/Ti-DCMS films are softer at H similar to 14 GPa with 0.03 less than= x less than= 0.24, and essentially stress-free (sigma similar to 0.5 GPa). Mass spectroscopy analyses at the substrate position reveal that the doubly-to-singly ionized metal-ion flux ratio during HIPIMS pulses is 0.05 for Si and 029 for Ti due to the difference between the second ionization potentials of Si and Ti vs. the first ionization potential of the sputtering gas. The average momentum transfer to the film growth surface per deposited atom per pulse less than p(d)greater than is similar to 20 x higher during Ti-HIPIMS/Si-DCMS, which results in significantly higher adatom mean-free paths (mfps) leading, in turn, to a phase-segregated nanocolumnar structure. In contrast, relatively low less than p(d)greater than values during Si-HIPIMS/Ti-DCMS provide near-surface mixing with lower adatom mfps to form Ti1-xSixN solid solutions over a very wide composition range with x up to 0.24. Relaxed lattice constants decrease linearly, in agreement with ab-initio calculations for random Ti1-xSixN alloys, with increasing x. (C) 2015 Elsevier B.V. All rights reserved.

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  • 42.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Al capping layers for non-destructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films2015In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 33, p. 05E101-1-05E101-9, article id 05E101Article in journal (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) compositional analyses of materials that have been air exposed typically require ion etching in order to remove contaminated surface layers. However, the etching step can lead to changes in sample surface and near-surface compositions due to preferential elemental sputter ejection and forward recoil implantation; this is a particular problem for metal/gas compounds and alloys such as nitrides and oxides. Here, we use TiN as a model system and compare XPS analysis results from three sets of polycrystalline TiN/Si(001) films deposited by reactive magnetron sputtering in a separate vacuum chamber. The films are either (a) air-exposed for ? 10 min prior to insertion into the ultra-high-vacuum (UHV) XPS system; (b) air-exposed and subject to ion etching, using different ion energies and beam incidence angles, in the XPS chamber prior to analysis; or (c) Al-capped in-situ in the deposition system prior to air-exposure and loading into the XPS instrument.We show that thin, 1.5-6.0 nm, Al capping layers provide effective barriers to oxidation and contamination of TiN surfaces, thus allowing non-destructive acquisition of high-resolution core-level spectra representative of clean samples, and, hence, correct bonding assignments. The Ti 2p and N 1s satellite features, which are sensitive to ion bombardment, exhibit high intensities comparable to those obtained from single-crystal TiN/MgO(001) films grown and analyzed in-situ in a UHV XPS system and there is no indication of Al/TiN interfacial reactions. XPS-determined N/Ti concentrations acquired from Al/TiN samples agree very well with Rutherford backscattering and elastic recoil analysis results while ion-etched air-exposed samples exhibit strong N loss due to preferential resputtering. The intensities and shapes of the Ti 2p and N 1s core level signals from Al/TiN/Si(001) samples do not change following long-term (up to 70 days) exposure to ambient conditions indicating that the thin Al capping layers provide stable surface passivation without spallation.

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  • 43.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Paradigm shift in thin-film growth by magnetron sputtering: From gas-ion to metal-ion irradiation of the growing film2019In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 37, no 6, article id 060801Article in journal (Refereed)
    Abstract [en]

    Ion refractory ceramic thin films grown at low temperatures by magnetron sputtering. However, in contrast to gas-ion bombardment, the effects of metal-ion irradiation on properties of refractory ceramic thin films have not been extensively studied due to (i) low metal-ion concentrations (a few percents) during standard direct-current magnetron sputtering (DCMS) and (ii) difficulties in separating metal-ion from gas-ion fluxes. Recently, the situation has changed dramatically, thanks to the development of highpower impulse magnetron sputtering (HiPIMS), which provides highly-ionized metal-ion plasmas. In addition, careful choice of sputtering conditions allows exploitation of gas-rarefaction effects such that the charge state, energy, and momentum of metal ions incident at the growing film surface can be tuned. This is possible via the use of pulsed substrate bias, synchronized to the metal-ion-rich portion of each HiPIMS pulse. In this review, the authors begin by summarizing the results of time-resolved mass spectrometry analyses performed at the substrate position during HiPIMS and HiPIMS/DCMS cosputtering of transition-metal (TM) targets in Ar and Ar/N-2 atmospheres. Knowledge of the temporal evolution of metal- and gas-ion fluxes is essential for precise control of the incident metal-ion energy and for minimizing the role of gas-ion irradiation. Next, the authors review results on the growth of binary, pseudobinary, and pseudoternary TM nitride alloys by metal-ion-synchronized HiPIMS. In contrast to gas ions, a fraction of which are trapped at interstitial sites, metal ions are primarily incorporated at lattice sites resulting in much lower compressive stresses. In addition, the closer mass match with the film-forming species results in more efficient momentum transfer and provides the recoil density and energy necessary to eliminate film porosity at low deposition temperatures. Several novel film-growth pathways have been demonstrated: (i) nanostructured N-doped bcc-CrN0.05 films combining properties typically associated with both metals and ceramics, (ii) fully-dense, hard, and stress-free Ti0.39Al0.61N, (iii) single-phase cubic Ti1-xSixN with the highest reported SiN concentrations, (iv) unprecedented AlN supersaturation in single-phase NaCl-structure V1-xAlxN, and (v) a dramatic increase in the hardness, due to selective heavy-metal ion bombardment during growth, of dense Ti0.92Ta0.08N films deposited with no external heating. (C) 2019 Author(s).

  • 44.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Materials Science Department and Frederick Seitz Materials Research Laboratory, University of Illinois, Urbana, USA; Department of Physics, University of Illinois, Urbana, USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Strategy for tuning the average charge state of metal ions incident at the growing film during HIPIMS deposition2015In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 116, p. 36-41Article in journal (Refereed)
    Abstract [en]

    Energy and time-dependent mass spectrometry is used to determine the relative number density of singly- and multiply-charged metal-ion fluxes incident at the substrate during high-power pulsed magnetron sputtering (HIPIMS) as a function of the average noble-gas ionization potential. Ti is selected as the sputtering target since the microstructure, phase composition, properties, and stress-state of Ti-based ceramic thin films grown by HIPIMS are known to be strongly dependent on the charge state of Tin+ (n = 1, 2, …) ions incident at the film growth surface. We find that the flux of Tin+ with n > 2 is insignificant; thus, we measure the Ti2+/Ti+ integrated flux ratio JTi2+ =JTi+ at the substrate position as a function of the choice of noble gase Ne, Ar, Kr, Xe, as well as Ne/Ar, Kr/Ar, and Xe/Ar mixtures – supporting the plasma. We demonstrate that by changing noble-gas mixtures, JTi2+ varies by more than two orders of magnitude with only a small change in JTi+ . This allows the ratio JTi2+ =JTi+ to be continuously tuned from less than 0.01 with Xe, which has a low first-ionization potential IP1, to 0.62 with Ne which has a high IP1. The value for Xe, IP1Xe= 12.16 eV, is larger than the first ionization potential of Ti, IP1Ti= 6.85 eV, but less than the second Ti ionization potential, IP2Ti= 13.62 eV. For Ne, however, IP1Ne= 21.63 eV is greater than both IP1Ti and IP2Ti. Therefore, the high-energy tail of the plasma-electron energy distribution can be systematically adjusted, allowing JTi2+/JTi+ to be controllably varied over a very wide range.

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  • 45.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhirkov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Control of the metal/gas ion ratio incident at the substrate plane during high-power impulse magnetron sputtering of transition metals in Ar2017In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 642, p. 36-40Article in journal (Refereed)
    Abstract [en]

    High-power impulse magnetron sputtering (HiPIMS) of materials systems with metal/gas-atom mass ratios m(Me)/m(g) near, or less than, unity presents a challenge for precise timing of synchronous substrate-bias pulses to select metal-ion irradiation of the film and, thus, reduce stress while increasing layer density during low-temperature growth. The problem stems from high gas-ion fluxes Fg+(t) at the substrate, which overlap with metal-ion fluxes FMe+(t). We use energy-and time-dependent mass spectrometry to analyze FMe+(t) and Fg+(t) for Group IVb transition-metal targets in Ar and show that the time-and energy-integrated metal/gas ion ratio NMe+/NAr+ at the substrate can be controlled over a wide range by adjusting the HiPIMS pulse length tau(ON), while maintaining the peak target current density J(T,peak) constant. The effect is a consequence of severe gas rarefaction which scales with J(T)(t). For Ti-HiPIMS, terminating the discharge at the maximum J(T)(t), corresponding to tau(ON) = 30 mu s, there is an essentially complete loss of Ar+ ion intensity, yielding NTi+/NAr+ similar to 60. With increasing tau(ON),J(T)(t) decreases and NTi+/NAr+ gradually decays, due to Ar refill, to similar to 1 with tau(ON) = 120 s. Time-resolved ion-energy distribution functions confirm that the degree of rarefaction depends on tau(ON): for shorter pulses, tau ONHTC/SUBTAG amp;lt; FORTITLEHTC_RETAIN 60 [rs, the original sputtered-atom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, which is in distinct contrast to longer pulses, tau(ON) amp;gt;= 60 mu s, for which the energy distributions collapse into narrow ther-malized peaks. Thus, optimizing the HiPIMS pulse width minimizes the gas-ion flux to the substrate independent of m(Me)/m(g).

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  • 46.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhirkov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Gas rarefaction effects during high power pulsed magnetron sputtering of groups IVb and VIb transition metals in Ar2017In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 35, no 6, article id 060601Article in journal (Refereed)
    Abstract [en]

    The authors use energy- and time-dependent mass spectrometry to analyze the evolution of metal- and gas-ion fluxes incident at the substrate during high-power pulsed magnetron sputtering (HiPIMS) of groups IVb and VIb transition-metal (TM) targets in Ar. For all TMs, the time-and energy-integrated metal/gas-ion ratio at the substrate plane NMe+/NAr+ increases with increasing peak target current density J(T,peak) due to rarefaction. In addition, NMe+/NAr+ exhibits a strong dependence on metal/gas-atom mass ratio m(Me)/m(g) and varies from similar to 1 for Ti (m(Ti)/m(Ar) = 1.20) to similar to 100 for W (m(W)/m(Ar) = 4.60), with J(T,peak) maintained constant at 1 A/cm(2). Time-resolved ion-energy distribution functions confirm that the degree of rarefaction scales with m(Me)/m(g): for heavier TMs, the original sputtered-atom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, which is in distinct contrast to lighter metals for which the energy distributions collapse into a narrow thermalized peak. Hence, precise timing of synchronous substrate-bias pulses, applied in order to reduce film stress while increasing densification, is critical for metal/gas combinations with m(Me)/m(g) near unity, while with m(Me)/m(g) amp;gt;amp;gt; 1, the width of the synchronous bias pulse is essentially controlled by the metal-ion time of flight. The good agreement between results obtained in an industrial system employing 440 cm(2) cathodes and a laboratory-scale system with a 20 cm(2) target is indicative of the fundamental nature of the phenomena. 

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  • 47.
    Greczynski, Grzegorz
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhirkov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Time evolution of ion fluxes incident at the substrate plane during reactive high-power impulse magnetron sputtering of groups IVb and VIb transition metals in Ar/N-22018In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 36, no 2, article id 020602Article in journal (Refereed)
    Abstract [en]

    Reactive transition-metal (TM) nitride film growth employing bias-synchronized high power impulse magnetron sputtering (HiPIMS) requires a detailed knowledge of the time evolution of metal-and gas-ion fluxes incident at the substrate plane in order to precisely tune momentum transfer and, hence, provide the recoil density and energy necessary to eliminate film porosity at low deposition temperatures without introducing significant film stress. Here, the authors use energy- and time-dependent mass spectrometry to analyze the evolution of metal-and gas-ion fluxes at the substrate plane during reactive HiPIMS sputtering of groups IVb and VIb TM targets in Ar/N-2 atmospheres. The time-and energy-integrated metal/gas ion ratio NMe+/Ng+ incident at the substrate is significantly lower for group IVb TMs (ranging from 0.2 for Ti to 0.9 for Hf), due to high N-2 reactivity which results in severely reduced target sputtering rates and, hence, decreased rarefaction. In contrast, for less reactive group VIb metals, sputtering rates are similar to those in pure Ar as a result of significant gas heating and high NMe+/Ng+ ratios, ranging from 2.3 for Cr to 98.1 for W. In both sets of experiments, the peak target current density is maintained constant at 1 A/cm(2). Within each TM group, NMe+/N(g+)scales with increasing metal-ion mass. For the group-VIb elements, sputtered-atom Sigmund-Thompson energy distributions are preserved long after the HiPIMS pulse, in contradistinction to group-IVb TMs for which the energy distributions collapse into narrow thermalized peaks. For all TMs, the N+ flux dominates that of N-2(+) ions, as the molecular ions are collisionally dissociated at the target, and N+ exhibits ion energy distribution functions resembling those of metal ions. The latter result implies that both N+ and Me+ species originate from the target. High-energy Ar+ tails, assigned to ionized reflected-Ar neutrals, are observed with heavier TM targets. Published by the AVS.

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  • 48.
    Hellgren, Niklas
    et al.
    Messiah Univ, PA 17055 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sortica, Mauricio A.
    Uppsala Univ, Sweden.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci & Technol, Taiwan.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    X-ray photoelectron spectroscopy analysis of TiBx (1.3 <= x <= 3.0) thin films2021In: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 39, no 2, article id 023403Article in journal (Refereed)
    Abstract [en]

    We report on a comprehensive analysis of titanium boride thin films by x-ray photoelectron spectroscopy (XPS). Films were grown by both direct current magnetron sputtering and high- power impulse magnetron sputtering from a compound TiB2 target in Ar discharge. By varying the deposition parameters, the film composition could be tuned over the wide range 1:3 &B/Ti &3:0, as determined by elastic recoil detection analysis and Rutherford backscattering spectrometry. By comparing spectra over this wide range of compositions, we can draw original conclusions about how to interpret XPS spectra of TiBx. By careful spectra deconvolution, the signals from Ti-Ti and B-B bonds can be resolved from those corresponding to stoichiometric TiB2. The intensities of the off-stoichiometric signals can be directly related to the B/Ti ratio of the films. Furthermore, we demonstrate a way to obtain consistent and quantum-mechanically accurate peak deconvolution of the whole Ti 2p envelope, including the plasmons, for both oxidized and sputter-cleaned samples. Due to preferential sputtering of Ti over B, the film B/Ti ratio is best determined without sputter etching of the sample surface. This allows accurate compositional determination, assuming that extensive levels of oxygen are not present in the sample. Fully dense films can be accurately quantified for at least a year after deposition, while underdense samples do not give reliable data if the O/Ti ratio on the unsputtered surface is *3:5. Titanium suboxides detected after sputter etching is further indicative of oxygen penetrating the sample, and quantification by XPS should not be trusted.

  • 49.
    Hellgren, Niklas
    et al.
    Messiah Coll, PA 17055 USA.
    Haasch, Richard T.
    University of Illinois, IL 61801 USA.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Interpretation of X-ray photoelectron spectra of carbon-nitride thin films: New insights from in situ XPS2016In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 108, p. 242-252Article in journal (Refereed)
    Abstract [en]

    We report on angular-resolved x-ray photoelectron spectroscopy (XPS) studies of magnetron sputtered CNx thin films, first in situ (without air exposure), then after air exposure (for time periods ranging from minutes to several years), and finally after Ar ion etching using ion energies ranging from 500 eV to 4 keV. The as-deposited films typically exhibit two strong N1s peaks corresponding to pyridine-like, and graphite-like, at similar to 398.2 eV and similar to 400.7 eV, respectively. Comparison between in situ and air-exposed samples suggests that the peak component at similar to 402-403 eV is due only to quaternary nitrogen and not oxidized nitrogen. Furthermore, peak components in the similar to 399-400 eV range cannot only be ascribed to nitriles or pyrrolic nitrogen as is commonly done. We propose that it can also be due to a polarization shift in pyridinic N, induced by surface water or hydroxides. Argon ion etching readily removes surface oxygen, but results also in a strong preferential sputtering of nitrogen and can cause amorphization of the film surface. The best methods for evaluating and interpreting the CNx film structure and composition with ex-situ XPS are discussed. (C) 2016 Elsevier Ltd. All rights reserved.

  • 50.
    Hellgren, Niklas
    et al.
    Messiah Coll, PA 17055 USA.
    Thörnberg, Jimmy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Zhirkov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sortica, Maurico A.
    Uppsala Univ, Sweden.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Univ Illinois, IL 61801 USA; Natl Taiwan Univ Sci and Technol, Taiwan.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rosén, Johanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    High-power impulse magnetron sputter deposition of TiBx thin films: Effects of pressure and growth temperature2019In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 169, article id UNSP 108884Article in journal (Refereed)
    Abstract [en]

    Titanium boride, TiBx thin films are grown in pure Ar discharges by high-power impulse magnetron sputtering (HiPIMS) from a compound TiB2 target Film compositions are determined by time-of-flight elastic recoil detection analysis and Rutherford backscattering spectrometry as a function of deposition temperature (T-s = 25-900 degrees C) and Ar pressure (p(Ar) = 0.67-2.67 Pa, 5-20 mTorr). For reference, films are also grown by direct current magnetron sputtering (dcMS) under similar conditions. The HiPIMS waveform, average target power P-T, and resulting film compositions are strongly dependent not only on P-Ar, but also on T-s. At high pressures the effect of varying T-s on P-T is minimal, while at lower P-Ar the effect of T-s is more pronounced, due to substrate-temperature-induced gas rarefaction. Films grown by HiPIMS at 0.67 Pa are understoichiometric, with B/Ti = 1.4-1.5, while at 2.67 Pa, B/Ti decreases from 2.4 to 1.4 as T-s increases from 25 to 900 degrees C. dcMS-deposited films are overstoichiometric (B/Ti similar or equal to 3) when grown at low pressures, and near-stoichiometric (B/Ti similar or equal to r 1.9-2.2) for higher P-Ar. All experimental results are explained by differences in the ionization potentials of sputtered Ti and B atoms, together with P-Ar- and T-s-dependent gas-phase scattering.

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