liu.seSearch for publications in DiVA
Change search
Link to record
Permanent link

Direct link
BETA
Greene, Joseph E
Alternative names
Publications (10 of 48) Show all publications
Greczynski, G., Zhirkov, I., Petrov, I., Greene, J. E. & Rosén, J. (2017). Gas rarefaction effects during high power pulsed magnetron sputtering of groups IVb and VIb transition metals in Ar. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 35(6), Article ID 060601.
Open this publication in new window or tab >>Gas rarefaction effects during high power pulsed magnetron sputtering of groups IVb and VIb transition metals in Ar
Show others...
2017 (English)In: 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) Published
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. 

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2017
Keywords
Time of flight mass spectrometry, Metalloids, Wave mechanics, Physical vapor deposition, Semiconductor device fabrication
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-143365 (URN)10.1116/1.4989674 (DOI)000415685300001 ()2-s2.0-85024128172 (Scopus ID)
Note

Funding Agencies|Swedish Research Council VR [2014-5790]; Aforsk Foundation [16-359]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [2009 00971]; Knut and Alice Wallenberg Foundation [KAW 2015.0043]

Available from: 2017-12-05 Created: 2017-12-05 Last updated: 2018-01-10Bibliographically approved
Sangiovanni, D., Mei, A. B., Hultman, L., Chirita, V., Petrov, I. & Greene, J. E. (2016). Ab Initio Molecular Dynamics Simulations of Nitrogen/VN(001) Surface Reactions: Vacancy-Catalyzed N-2 Dissociative Chemisorption, N Adatom Migration, and N-2 Desorption. The Journal of Physical Chemistry C, 120(23), 12503-12516
Open this publication in new window or tab >>Ab Initio Molecular Dynamics Simulations of Nitrogen/VN(001) Surface Reactions: Vacancy-Catalyzed N-2 Dissociative Chemisorption, N Adatom Migration, and N-2 Desorption
Show others...
2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 23, p. 12503-12516Article in journal (Refereed) Published
Abstract [en]

We use density-functional ab initio molecular dynamics to investigate the kinetics of N/VN(001) surface reactions at temperatures ranging from 1600 to 2300 K. N adatoms (N-ad) on VN(001) favor epitaxial atop-V positions and diffuse among them by transiting through 4-fold hollow (FFH) sites, at which they are surrounded by two V and two N surface atoms. After several atop-V -amp;gt; FFH -amp;gt; atop-V jumps, isolated N adatoms bond strongly with an underlying N surface (N-surf) atom. Frequent N-ad/N-surf pair exchange reactions lead to N-2 desorption, which results in the formation of an anion surface vacancy. N vacancies rapidly migrate via in-plane (110) jumps and act as efficient catalysts for the dissociative chemisorption of incident N-2 molecules. During exposure of VN(001) to incident atomic N gas atoms, N-ad/N-ad recombination and desorption is never observed, despite a continuously high N monomer surface coverage. Instead, N-2 desorption is always initiated by a N adatom removing a N surface atom or by energetic N gas atoms colliding with N-ad or N-surf atoms. Similarities and differences between: N/VN(001) vs. previous N/TiN(001) results, discussed on the basis of temperature-dependent ab initio electronic structures and chemical bonding, provide insights for controlling the reactivity of NaCl-structure transition-metal nitride (001) surfaces via electron-concentration tuning.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2016
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:liu:diva-130283 (URN)10.1021/acs.jpcc.6b02652 (DOI)000378196200021 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation (Isotope Project) [2011.0094]; Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2014-5790, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials (through Swedens innovation agency VINNOVA) [MatLiU 2009-00971]

Available from: 2016-08-01 Created: 2016-07-28 Last updated: 2019-06-28
Sangiovanni, D., Hultman, L., Chirita, V., Petrov, I. & Greene, J. E. (2016). Effects of phase stability, lattice ordering, and electron density on plastic deformation in cubic TiWN pseudobinary transition-metal nitride alloys. Acta Materialia, 103, 823-835
Open this publication in new window or tab >>Effects of phase stability, lattice ordering, and electron density on plastic deformation in cubic TiWN pseudobinary transition-metal nitride alloys
Show others...
2016 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 103, p. 823-835Article in journal (Refereed) Published
Abstract [en]

We carry out density functional theory calculations to compare the energetics of layer glide, as well as stress vs. strain curves, for cubic Ti0.5W0.5N pseudobinary alloys and reference B1-structure TiN. Irrespective of the degree of ordering on the metal sublattice, the hardness and stiffness of Ti0.5W0.5, as estimated by stress strain results and resistance to layer glide, are comparable to that of the parent binary TiN, while ductility is considerably enhanced. After an initial elastic response to an applied load, the pseudobinary alloy deforms plastically, thus releasing accumulated mechanical stress. In contrast, stress continues to increase linearly with strain in TiN. Layer glide in Ti0.5W0.5N is promoted by a high valence-electron concentration which enables the formation of strong metallic bonds within the slip direction upon deformation. [1111-oriented Ti0.5W0.5N layers characterized by high local metal-sublattice ordering exhibit low resistance to slip along < 110 > directions due to energetically favored formation of (111) hexagonal stacking faults. This is consistent with the positive formation energy of < 111 >-ordered Tio.5W0.5N with respect to mixing of cubic-BI TiN and hexagonal WC-structure WN. In the cubic pseudobinary alloy, slip occurs parallel, as well as orthogonal, to the resolved applied stress at the interface between layers with the lowest friction. We suggest that analogous structural metastability (mixing cubic and hexagonal TM nitride binary phases) and electronic (high valence electron concentration) effects are responsible for the enhanced toughness recently demonstrated experimentally for cubic single-crystal pseudobinary V0.5W0.5N and V0.5MocoN epitaxial layers. (c) 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
PERGAMON-ELSEVIER SCIENCE LTD, 2016
Keywords
Nitrides; Toughness Phase stability; Density functional theory (DFT); Electronic structure
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-124462 (URN)10.1016/j.actamat.2015.10.039 (DOI)000367630500081 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2011.0094]; Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2014-5790, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials through Swedens innovation agency VINNOVA [2009-00971]

Available from: 2016-02-02 Created: 2016-02-01 Last updated: 2019-06-28
Edström, D., Sangiovanni, D., Hultman, L., Petrov, I., Greene, J. E. & Chirita, V. (2016). Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 34(4), 041509-1-041509-9
Open this publication in new window or tab >>Large-scale molecular dynamics simulations of TiN/TiN(001) epitaxial film growth
Show others...
2016 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
AMER INST PHYSICS, 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-130405 (URN)10.1116/1.4953404 (DOI)000379588000027 ()
Note

Funding Agencies|Swedish Research Council (VR) Linkoping Linnaeus Initiative LiLi-NFM [2008-6572, 2009-00971, 2013-4018, 2014-5790]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials; Knut and Alice Wallenberg Foundation (Isotope Project)

Available from: 2016-08-15 Created: 2016-08-05 Last updated: 2019-06-28
Sangiovanni, D., Tasnadi, F., Hultman, L., Petrov, I., Greene, J. E. & Chirita, V. (2016). N and Ti adatom dynamics on stoichiometric polar TiN(111) surfaces. Surface Science, 649, 72-79
Open this publication in new window or tab >>N and Ti adatom dynamics on stoichiometric polar TiN(111) surfaces
Show others...
2016 (English)In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 649, p. 72-79Article in journal (Refereed) Published
Abstract [en]

We use molecular dynamics (MD) based on the modified embedded atom method (MEAM) to determine diffusion coefficients and migration pathways for Ti and N adatoms (Ti-ad and N-ad) on TiN(111). The reliability of the classical model-potential is verified by comparison with density functional theory (DFT) results at 0 K. MD simulations carried out at temperatures between 600 and 1800 K show that both Ti-ad and N-ad favor fcc surface sites and migrate among them by passing through metastable hcp positions. We find that N-ad species are considerably more mobile than Ti-ad on TiN(111); contrary to our previous results on TiN(001). In addition, we show that lattice vibrations at finite temperatures strongly modify the potential energy landscape and result in smaller adatom migration energies, E-a = 1.03 for Ti-ad and 0.61 eV for N-ad, compared to 0 K values E-aOK = 1.55 (Ti-ad) and 0.79 eV (N-ad). We also demonstrate that the inclusion of dipole corrections, neglected in previous DFT calculations, is necessary in order to obtain the correct formation energies for polar surfaces such as TiN(111). (C) 2016 Elsevier B.V. All rights reserved.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE BV, 2016
Keywords
Surface diffusion; Nitrides; Molecular dynamics; Density functional theory; Polar surfaces
National Category
Theoretical Chemistry
Identifiers
urn:nbn:se:liu:diva-130423 (URN)10.1016/j.susc.2016.01.031 (DOI)000379097000012 ()
Note

Funding Agencies|Knut and Alice Wallenberg Foundation [2011.0094]; Swedish Research Council (VR) [2014-5790]; Linkoping Linnaeus Initiative LiLi-NFM [2008-6572]; Swedish Government Strategic Research Area Grant in Materials Science on Advanced Functional Materials through Swedens innovation agency VINNOVA [MatLiU 2009-00971]

Available from: 2016-08-07 Created: 2016-08-05 Last updated: 2019-06-28
Greczynski, G., Lu, J., Tengstrand, O., Petrov, I., Greene, J. E. & Hultman, L. (2016). Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity. Scripta Materialia, 122, 40-44
Open this publication in new window or tab >>Nitrogen-doped bcc-Cr films: Combining ceramic hardness with metallic toughness and conductivity
Show others...
2016 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 122, p. 40-44Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Elsevier Ltd, 2016
Keywords
CrN, HIPIMS, Ion mass spectrometry, Magnetron sputtering, Resistivity, Thin films, Toughness, Transition-metal nitrides
National Category
Materials Chemistry
Identifiers
urn:nbn:se:liu:diva-129248 (URN)10.1016/j.scriptamat.2016.05.011 (DOI)2-s2.0-84971328580 (Scopus ID)
Note

Funding Agencies|#2011.0143, Swedish Research Council; 2013-4018, Swedish Research Council; 2014-5790, Swedish Research Council

Available from: 2016-06-14 Created: 2016-06-14 Last updated: 2017-11-28
Greczynski, G., Petrov, I., Greene, J. E. & Hultman, L. (2015). Al capping layers for non-destructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 33, 05E101-1-05E101-9, Article ID 05E101.
Open this publication in new window or tab >>Al capping layers for non-destructive x-ray photoelectron spectroscopy analyses of transition-metal nitride thin films
2015 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
American Vacuum Society, 2015
Keywords
XPS; TiN; capping layers; oxidation protection; sputtering; surface passivation
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-118598 (URN)10.1116/1.4916239 (DOI)000361229000001 ()
Funder
VINNOVA, 2005-02666EU, European Research Council, 227754Knut and Alice Wallenberg Foundation, 2011.0143Swedish Research Council, 2014-5790
Available from: 2015-06-02 Created: 2015-06-02 Last updated: 2017-12-04Bibliographically approved
Greczynski, G., Patscheider, J., Lu, J., Alling, B., Ektarawong, A., Jensen, J., . . . Hultman, L. (2015). Control of Ti1-xSixN nanostructure via tunable metal-ion momentum transfer during HIPIMS/DCMS co-deposition. Surface & Coatings Technology, 280, 174-184
Open this publication in new window or tab >>Control of Ti1-xSixN nanostructure via tunable metal-ion momentum transfer during HIPIMS/DCMS co-deposition
Show others...
2015 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 280, p. 174-184Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2015
Keywords
HIPIMS; HPPMS; TiSiN; Magnetron sputtering; Ionized PVD
National Category
Materials Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-122787 (URN)10.1016/j.surfcoat.2015.09.001 (DOI)000363825100021 ()
Note

Funding Agencies|European Research Council (ERC) [227754]; VINN Excellence Center Functional Nanoscale Materials (FunMat) Grant [2005-02666]; Knut and Alice Wallenberg Foundation Grant [2011.0143]; Swedish Government Strategic Faculty Grant in Materials Science; Swedish Research Council (VR) Project [2014-5790, 621-2011-4417, 330-2014-6336]

Available from: 2015-11-23 Created: 2015-11-23 Last updated: 2018-08-14
Mei, A. B., Hellman, O., Wireklint, N., Schlepuetz, C. M., Sangiovanni, D., Alling, B., . . . Greene, J. E. (2015). Dynamic and structural stability of cubic vanadium nitride. Physical Review B. Condensed Matter and Materials Physics, 91(5), 054101
Open this publication in new window or tab >>Dynamic and structural stability of cubic vanadium nitride
Show others...
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 91, no 5, p. 054101-Article in journal (Refereed) Published
Abstract [en]

Structural phase transitions in epitaxial stoichiometric VN/MgO(011) thin films are investigated using temperature-dependent synchrotron x-ray diffraction (XRD), selected-area electron diffraction (SAED), resistivity measurements, high-resolution cross-sectional transmission electron microscopy, and ab initio molecular dynamics (AIMD). At room temperature, VN has the B1 NaCl structure. However, below T-c = 250 K, XRD and SAED results reveal forbidden (00l) reflections of mixed parity associated with a noncentrosymmetric tetragonal structure. The intensities of the forbidden reflections increase with decreasing temperature following the scaling behavior I proportional to (T-c - T)(1/2). Resistivity measurements between 300 and 4 K consist of two linear regimes resulting from different electron/phonon coupling strengths in the cubic and tetragonal-VN phases. The VN transport Eliashberg spectral function alpha F-2(tr)(h omega), the product of the phonon density of states F(h omega) and the transport electron/phonon coupling strength alpha(2)(tr)(h omega), is determined and used in combination with AIMD renormalized phonon dispersion relations to show that anharmonic vibrations stabilize the NaCl structure at T greater than T-c. Free-energy contributions due to vibrational entropy, often neglected in theoretical modeling, are essential for understanding the room-temperature stability of NaCl-structure VN, and of strongly anharmonic systems in general.

Place, publisher, year, edition, pages
American Physical Society, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:liu:diva-114566 (URN)10.1103/PhysRevB.91.054101 (DOI)000348872600001 ()
Note

Funding Agencies|Swedish Research Council (VR) program [637-2013-7296, 2014-5790, 2009-00971, 2013-4018]; Swedish Government Strategic Research Area Grant in Materials Science [SFO Mat-LiU 2009-00971]; DOE Office of Science by Argonne National Laboratory [DE-AC02-06CH11357]

Available from: 2015-03-02 Created: 2015-02-26 Last updated: 2019-06-28
Fager, H., Howe, B. M., Greczynski, G., Jensen, J., Mei, A. B., Lu, J., . . . Petrov, I. (2015). Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, 33(5), 05E103-1-05E103-9
Open this publication in new window or tab >>Novel hard, tough HfAlSiN multilayers, defined by alternating Si bond structure, deposited using modulated high-flux, low-energy ion irradiation of the growing film
Show others...
2015 (English)In: 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) Published
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.

Place, publisher, year, edition, pages
A V S AMER INST PHYSICS, 2015
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:liu:diva-121905 (URN)10.1116/1.4920980 (DOI)000361229000003 ()
Note

Funding Agencies|U.S. Department of Energy [DE-FG02-07ER46453, DE-FG02-07ER46471]; Swedish Foundation for Strategic Research project Designed Multicomponent Coatings, MultiFil; U.S. Department of Defense Science, Mathematics, and Research for Transformation program; Swedish Government Strategic Research Area Grant (SFO MAT-LiU) on Advanced Functional Materials; Swedish Research Council (VR) [2009-00971]

Available from: 2015-10-13 Created: 2015-10-12 Last updated: 2017-12-01
Organisations

Search in DiVA

Show all publications