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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.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hall-Wilton, R.
    European Spallat Source ESS AB.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mixing thermodynamics of TM(1-x)Gd(x)N (TM=Ti, Zr, Hf) from first principles2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, no 24, p. 241911-Article in journal (Refereed)
    Abstract [en]

    The mixing thermodynamics of GdN with TiN, ZrN, and HfN is studied using first-principles methods. We find that while Ti(1-x)Gd(x)N has a strong preference for phase separation due to the large lattice mismatch, Zr(1-x)Gd(x)N and Hf(1-x)Gd(x)N readily mix, possibly in the form of ordered compounds. In particular, ZrGdN(2) is predicted to order in a rocksalt counterpart to the L1(1) structure at temperatures below 1020 K. These mixed nitrides are promising candidates as neutron absorbing, thermally and chemically stable, thin film materials.

  • 2.
    Andersen, Ken
    et al.
    European Spallation Source ESS AB, Lund, Sweden.
    Bigault, Thierry
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Buffet, J. C.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Correa, Jonathan
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Hall-Wilton, Richard
    European Spallation Source ESS AB, Lund, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Guerard, Bruno
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Khaplanov, Anton
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Kirstein, Oliver
    Linköping University.
    Piscitelli, Fransesco
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    van Esch, P.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Vettier, Christian
    European Spallation Source, Lund, Sweden.
    10B multi-grid proportional gas counters for large area thermal neutrondetectors2013In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 720, p. 116-121Article in journal (Refereed)
    Abstract [en]

    3He was a popular material in neutrons detectors until its availability dropped drastically in 2008. The development of techniques based on alternative convertors is now of high priority for neutron research institutes. Thin films of 10B or 10B4C have been used in gas proportional counters to detect neutrons, but until now, only for small or medium sensitive area. We present here the multi-grid design, introduced at the ILL and developed in collaboration with ESS for LAN (large area neutron) detectors. Typically thirty 10B4C films of 1 μm thickness are used to convert neutrons into ionizing particles which are subsequently detected in a proportional gas counter. The principle and the fabrication of the multi-grid are described and some preliminary results obtained with a prototype of 200 cm×8 cm are reported; a detection efficiency of 48% has been measured at 2.5 Å with a monochromatic neutron beam line, showing the good potential of this new technique.

  • 3.
    Beckers, Manfred
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Baehtz, Carsten
    Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf.
    Martins, R.M.S.
    Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf.
    Persson, Per O. Å.
    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.
    Möller, W.
    Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf.
    The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti-Al-N thin films2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 6, p. 064915-Article in journal (Refereed)
    Abstract [en]

    Ternary Ti-Al-N films were deposited onto Al2O3 (0001) substrates by reactive co‑sputtering from elemental Ti and Al targets and analyzed by in situ and ex situ x-ray scattering, Rutherford backscattering spectroscopy, transmission electron microscopy and x-ray photoemission spectroscopy. The deposition parameters were set to values that yield Ti:Al:N ratios of 2:1:1 and 4:1:3 at room temperature. 2TiAlN depositions at 675 °C result in epitaxial Ti2AlN growth with basal planes parallel to the substrate surface. Nominal 4TiAl3N depositions at 675 °C and above, however, yield TiN and Ti2AlN domains due to Al loss to the vacuum. Depositions at a lower temperature of 600 °C yield films with correct 4:1:3 stoichiometry, but Ti4AlN3 formation is supposedly prevented by insufficient adatom mobility. Instead, an incoherent Tin+1AlNn structure with random twinned stacking sequences n is obtained, that exhibits both basal plane orientations parallel as well as nearly perpendicular to the substrate interface. X‑ray photoemission spectroscopy shows that in contrast to stoichiometric nitrides the Al is metallically bonded and hence acts as twinning plane within the Tin+1AlNn stackings. Domains with perpendicular basal plane orientation overgrowth those with parallel ones in a competitive growth mode. The resulting morphology is a combination of smooth‑surfaced parallel basal plane orientation domains interrupted by repeated facetted hillock-like features with perpendicular basal plane orientation.

  • 4.
    Bigault, Thierry
    et al.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Buffet, J. C.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Correa, Jonathan
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Hall-Wilton, Richard
    European Spallation Source ESS AB, Lund, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Guérard, Bruno
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Khaplanov, Anton
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Piscitelli, Fransesco
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    van Esch, P.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    10B multi-grid proportional gas counters for large area thermal neutron detectors2012In: Neutron News, ISSN 1044-8632, E-ISSN 1931-7352, Vol. 23, no 4, p. 20-24Article in journal (Refereed)
  • 5.
    Birch, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Buffet, J. -C.
    Institute Laue Langevin, France.
    Clergeau, J. -F.
    Institute Laue Langevin, France.
    van Esch, P.
    Institute Laue Langevin, France.
    Ferraton, M.
    Institute Laue Langevin, France.
    Guerard, B.
    Institute Laue Langevin, France.
    Hall-Wilton, R.
    European Spallat Source, Sweden; Mid Sweden University, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. European Spallat Source, Sweden.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Khaplanov, A.
    Institute Laue Langevin, France; European Spallat Source, Sweden.
    Piscitelli, F.
    Institute Laue Langevin, France; European Spallat Source, Sweden.
    Investigation of background in large-area neutron detectors due to alpha emission from impurities in aluminium2015In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, p. 1-14Article in journal (Refereed)
    Abstract [en]

    Thermal neutron detector based on films of (B4C)-B-10 have been developed as an alternative to He-3 detectors. In particular, The Multi-Grid detector concept is considered for future large area detectors for ESS and ILL instruments. An excellent signal-to-background ratio is essential to attain expected scientific results. Aluminium is the most natural material for the mechanical structure of of the Multi-Grid detector and other similar concepts due to its mechanical and neutronic properties. Due to natural concentration of alpha emitters, however, the background from alpha particles misidentified as neutrons can be unacceptably high. We present our experience operating a detector prototype affected by this issue. Monte Carlo simulations have been used to confirm the background as alpha particles. The issues have been addressed in the more recent implementations of the Multi-Grid detector by the use of purified aluminium as well as Ni-plating of standard aluminium. The result is the reduction in background by two orders of magnitude. A new large-area prototype has been built incorporating these modifications.

  • 6.
    Birch, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Buffet, J. C.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Correa, Jonathan
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    van Esch, P.
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Guerard, Bruno
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Hall-Wilton, Richard
    European Spallation Source ESS AB, Lund, Sweden.
    Höglund, Carina
    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.
    Khaplanov, Anton
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    Piscitelli, Fransesco
    Institut Laue Langevin, Grenoble, Cedex 9, France.
    (B4C)-B-10 Multi-Grid as an Alternative to He-3 for Large Area Neutron Detectors2013In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 60, no 2, p. 871-878Article in journal (Refereed)
    Abstract [en]

    Despite its present shortage, 3He continues to be the most common neutron converter for detectors in neutron scattering science. However, it is obvious that the development of large area neutron detectors based on alternative neutron converters is rapidly becoming a matter of urgency. In the technique presented here, grids each comprising 28 10B4C layers (each 1 μm thick) are used to convert neutrons into ionizing particles which are subsequently detected in proportional gas counters. The total active area of the prototype is 8 cm × 200 cm. To instrument this detector 4.6 m2 of 10B-enriched boron carbide were coated onto aluminium blades using a DC magnetron sputtering machine.

  • 7.
    Birch, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Buffet, J.-C.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Clergeau, J.-F.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Correa, J.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    van Esch, P.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Ferraton, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Guerard, B.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Halbwachs, J.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Hall-Wilton, R.
    European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Khaplanov, A.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France; European Spallation Source ESS AB, P.O Box 176, SE-221 00 Lund, Sweden.
    Koza, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Piscitelli, F.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    Zbiri, M.
    Institute Laue Langevin, Rue Jules Horowitz, FR-38000 Grenoble, France.
    In-beam test of the Boron-10 Multi-Grid neutron detector at the IN6 time-of-flight spectrometer at the ILL2014In: INTERNATIONAL WORKSHOP ON NEUTRON OPTICS AND DETECTORS (NOPandD 2013), IOP Publishing: Conference Series / Institute of Physics (IoP) , 2014, Vol. 528, no 012040Conference paper (Refereed)
    Abstract [en]

    A neutron detector concept based on solid layers of boron carbide enriched in 1 B has been in development for the last few years as an alternative for He-3 by collaboration between the ILL, ESS and Linkoping University. This Multi-Grid detector uses layers of aluminum substrates coated with (B4C)-B-10 on both sides that are traversed by the incoming neutrons. Detection is achieved using a gas counter readout principle. By segmenting the substrate and using multiple anode wires, the detector is made inherently position sensitive. This development is aimed primarily at neutron scattering instruments with large detector areas, such as time-of-flight chopper spectrometers. The most recent prototype has been built to be interchangeable with the He-3 detectors of IN6 at ILL. The 1 B detector has an active area of 32 x 48 cm(2). It was installed at the IN6 instrument and operated for several weeks, collecting data in parallel with the regularly scheduled experiments, thus providing the first side-by-side comparison with the conventional He-3 detectors. Results include an efficiency comparison, assessment of the in-detector scattering contribution, sensitivity to gamma-rays and the signal-to-noise ratio in time-of-flight spectra. The good expected performance has been confirmed with the exception of an unexpected background count rate. This has been identified as natural alpha activity in aluminum. New convertor substrates are under study to eliminate this source of background.

  • 8.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Growth and Phase Stability Studies of Epitaxial Sc-Al-N and Ti-Al-N Thin Films2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    ¨This Thesis treats the growth and characterization of ternary transition metal nitride thin films. The aim is to probe deep into the Ti-Al-N system and to explore novel Sc-Al-N compounds. Thin films were epitaxially grown by reactive dual magnetron sputtering from elemental targets onto single-crystal substrates. Ion beam analyses were used for compositional analysis and depth profiling. Different X-ray diffraction techniques were employed, ex situ using Cu radiation and in situ during deposition using synchrotron radiation, to achieve information about phases, texture, and thickness of films, and to follow roughness evolution of layers during and after growth. Transmission electron microscopy was used for overview and lattice imaging, and to obtain lattice structure information by electron diffraction.

    In the Sc-Al-N system, the perovskite Sc3AlN was for the first time synthesized as a thin film and in single phase, with a unit cell of 4.40 Å. The hardness was found to be 14.2 GPa, the elastic modulus 21 GPa, and the room temperature resistivity 41.2 μΩcm. Cubic solid solutions of Sc1-xAlxN can be synthesized with AlN molar fraction up to ~60%. Higher AlN contents yield three different epitaxial relations to ScN(111), namely, #1 Sc1-xAlxN(0001) || ScN(111) with Sc1-xAlxN[11210] || ScN[110], #2 Sc1-xAlxN(1011) || ScN(110) with Sc1-xAlxN[1210] || ScN[110], and #3 Sc1-xAlxN(1011) || ScN(113). An in situ deposition and annealing study of cubic Sc0.57Al0.43N films showed volume induced phase separation into ScN and wurtzite structure AlN, via nucleation and growth at the domain boundaries. The first indications for phase separation are visible at 1000 °C, and the topotaxial relationship between the binaries after phase separation is AlN(0001) || ScN(001) and AlN<01ɸ10> || ScN <1ɸ10>. This is compared with Ti1-xAlxN, for which an electronic structure driving force leads to spinodal decomposition into isostructural TiN and AlN already at 800 °C. First principles calculations explain the results on a fundamental physics level. Up to ~22% ScN can under the employed deposition conditions be dissolved into wurtzite Sc1-xAlxN films, while retaining a single-crystal structure and with lattice parameters matching calculated values.

    In the Ti-Al-N system, the Ti2AlN phase was synthesized epitaxially by solid state reaction during interdiffusion between sequentially deposited layers of AlN(0001) and Ti(0001). When annealing the sample, N and Al diffused into the Ti layer, forming Ti3AlN(111) at 400 ºC and Ti2AlN(0001) at 500 ºC. The Ti2AlN formation temperature is 175 ºC lower than earlier reported results. Another way of forming Ti2AlN phase is by depositing understoichiometric TiNx at 800 °C onto Al2O3(0001). An epitaxial Ti2Al(O,N) (0001) oxynitride forms close to the interface between film and substrate through a solid state reaction. Ti4AlN3 was, however, not possible to synthesize when depositing films with a Ti:Al:N ratio of 4:1:3 due to competing reactions. A substrate temperature of 600 ºC yielded an irregularly stacked Tin+1AlNn layered structure because of the low mobility of Al ad-atoms. An increased temperature led to Al deficiency due to outdiffusion of Al atoms, and formation of the Ti2AlN phase and a Ti1-xAlxN cubic solid solution.

    List of papers
    1. Sc3AlN: A New Perovskite
    Open this publication in new window or tab >>Sc3AlN: A New Perovskite
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    2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2008, no 8, p. 1193-1195Article in journal (Refereed) Published
    Abstract [en]

    Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc–Al–N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 μm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a roomtemperature electrical resistivity of 41.2 μΩ cm.

    Keywords
    Crystal growth, Density functional theory, Electron microscopy, Perovskite nitride phases, Thin films
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17106 (URN)10.1002/ejic.200701356 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    2. Cubic Sc1-xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111)
    Open this publication in new window or tab >>Cubic Sc1-xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111)
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    2009 (English)In: JOURNAL OF APPLIED PHYSICS, ISSN 0021-8979, Vol. 105, no 11, p. 132862-Article in journal (Refereed) Published
    Abstract [en]

    Reactive magnetron sputter epitaxy was used to deposit thin solid films of Sc1-xAlxN (0 andlt;= x andlt;= 1) onto MgO(111) substrates with ScN(111) seed layers. Stoichiometric films were deposited from elemental Sc and Al targets at substrate temperatures of 600 S C. The films were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection analysis, x-ray diffraction, and transmission electron microscopy. Results show that rocksalt structure (c)-Sc1-xAlxN solid solutions with AlN molar fractions up to similar to 60% can be synthesized. For higher AlN contents, the system phase separates into c- and wurtzite structure (w)-Sc1-xAlxN domains. The w-domains are present in three different orientations relative to the seed layer, namely, Sc1-xAlxN(0001)parallel to ScN(111) with Sc1-xAlxN[(1) over bar2 (1) over bar0]parallel to ScN[1 (1) over bar0], Sc1-xAlxN(10 (1) over bar1)parallel to ScN(111) with Sc1-xAlxN[(1) over bar2 (1) over bar0]parallel to ScN[1 (1) over bar0], and Sc1-xAlxN(10 (1) over bar1)parallel to ScN(113). The results are compared to first-principles density functional theory calculations for the mixing enthalpies of c-, w-, and zinc blende Sc0.50Al0.50N solid solutions, yielding metastability with respect to phase separation for all temperatures below the melting points of AlN and ScN.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-19664 (URN)10.1063/1.3132862 (DOI)
    Note
    Original Publication: Carina Höglund, Javier Bareno, Jens Birch, Björn Alling, Zsolt Czigany and Lars Hultman, Cubic Sc1-xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111), 2009, JOURNAL OF APPLIED PHYSICS, (105), 11, 132862. http://dx.doi.org/10.1063/1.3132862 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2009-07-10 Created: 2009-07-10 Last updated: 2016-08-31
    3. Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions
    Open this publication in new window or tab >>Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions
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    2010 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 22, p. 224101-Article in journal (Refereed) Published
    Abstract [en]

    Thin solid films of metastable rocksalt structure (c-) Sc1-xAlxN and Ti1-xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N(111) and Ti0.51Al0.49N(111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using X-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000 °C – 1100 °C into non-isostructural c-ScN and wurtzite-structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800 °C – 1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001) || ScN(001) and AlN<01ɸ10> || ScN<1ɸ10>. First principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.

    Keywords
    TiAlN, ScAlN, spinodal decomposition, nitrides, TiN, ScN, AlN, XRD, TEM, first-principles, phase separation, meta stable
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56270 (URN)10.1103/PhysRevB.81.224101 (DOI)000278300900004 ()
    Note
    Original Publication: Carina Höglund, Björn Alling, Jens Birch, Manfred Beckers, Per O. Å. Persson, Carsten Baehtz, Zsolt Czigány, Jens Jensen and Lars Hultman, Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions, 2010, Physical Review B. Condensed Matter and Materials Physics, (81), 22, 224101. http://dx.doi.org/10.1103/PhysRevB.81.224101 Copyright: American Physical Society http://www.aps.org/ Available from: 2010-05-06 Created: 2010-05-06 Last updated: 2017-12-12
    4. Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: structural characterization and first-principles calculations
    Open this publication in new window or tab >>Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: structural characterization and first-principles calculations
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    2010 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 12, p. 123515-Article in journal (Refereed) Published
    Abstract [en]

    AlN(0001) was alloyed with ScN with molar fractions up to ~22%, while retaining a singlecrystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ~50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt-structure Sc1-xAlxN(111) films. The experimental results are analyzed with ion beam analysis, X-ray diffraction, and transmission electron microscopy, together with ab-initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.

    Place, publisher, year, edition, pages
    American Institute of Physics, 2010
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56272 (URN)10.1063/1.3448235 (DOI)000279993900042 ()
    Note
    Original Publication: Carina Höglund, Jens Birch, Björn Alling, Javier Bareño, Zsolt Czigány, Per O. Å. Persson, Gunilla Wingqvist, Agne Zukauskaite and Lars Hultman, Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: structural characterization and first-principles calculations, 2010, Journal of Applied Physics, (107), 12, 123515. http://dx.doi.org/10.1063/1.3448235 Copyright: American Institute of Physics http://www.aip.org/ Available from: 2010-05-06 Created: 2010-05-06 Last updated: 2017-12-12Bibliographically approved
    5. Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films
    Open this publication in new window or tab >>Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films
    Show others...
    2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 174106Article in journal (Refereed) Published
    Abstract [en]

    The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and α-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3(0001) at 200 °C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400 °C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500 °C resulted in a phase transformation into Ti2AlN(0001) after only 5 min.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17105 (URN)10.1063/1.2731520 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    6. Ti2Al(O,N) formation by solid state reaction between substoichiometric TiN thin films and Al2O3(0001) substrates
    Open this publication in new window or tab >>Ti2Al(O,N) formation by solid state reaction between substoichiometric TiN thin films and Al2O3(0001) substrates
    2011 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 8, p. 2421-2425Article in journal (Refereed) Published
    Abstract [en]

    Titanium nitride TiNx (0.1 ≤ x ≤ 1) thin films were deposited onto Al2O3(0001) substrates using reactive magnetron sputtering at substrate temperatures (Ts) ranging from 800 ºC to 1000 ºC and N2 partial pressures (pN2) between 0.1 and 1.0 mTorr. It is found that Al and O from the substrates diffuse into the substoichiometric TiNx films during deposition. Solid state reactions between the film and substrate result in the formation of Ti2O and Ti3Al domains at low N2 partial pressures, while for increasing pN2, the Ti2AlN MAX phase nucleates and grows together with TiNx. Depositions at increasingly stoichiometric conditions result in a decreasing incorporation of the substrate species into the growing film. Eventually, a stoichiometric deposition gives a stable TiN(111) || Al2O3(0001) structure without the incorporation of substrate species. Growth at Ts 1000 ºC yields Ti2AlN(0001), leading to a reduced incorporation of substrate species compared to films grown at 900 ºC, but contains also Ti2AlN(101ɸ3) grains. Finally, the Ti2AlN domains incorporate O, likely on the N site, such that a MAX phase oxynitride Ti2Al(O,N) is formed. The results were obtained by a combination of structural methods, including X-ray diffraction (XRD) and (scanning) transmission electron microscopy ((S)TEM), together with spectroscopy methods, which comprise elastic recoil detection analysis (ERDA), energy dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS).

    Place, publisher, year, edition, pages
    Elsevier, 2011
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-56273 (URN)10.1016/j.tsf.2010.12.002 (DOI)000287631500007 ()
    Note
    Original Publication: P. O. Å. Persson, Carina Höglund, Jens Birch and Lars Hultman, Ti2Al(O,N) formation by solid state reaction between substoichiometric TiN thin films and Al2O3(0001) substrates, 2011, Thin Solid Films, (519), 2421-2425. http://dx.doi.org/10.1016/j.tsf.2010.12.002 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2010-05-06 Created: 2010-05-06 Last updated: 2017-12-12
    7. The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti-Al-N thin films
    Open this publication in new window or tab >>The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti-Al-N thin films
    Show others...
    2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 6, p. 064915-Article in journal (Refereed) Published
    Abstract [en]

    Ternary Ti-Al-N films were deposited onto Al2O3 (0001) substrates by reactive co‑sputtering from elemental Ti and Al targets and analyzed by in situ and ex situ x-ray scattering, Rutherford backscattering spectroscopy, transmission electron microscopy and x-ray photoemission spectroscopy. The deposition parameters were set to values that yield Ti:Al:N ratios of 2:1:1 and 4:1:3 at room temperature. 2TiAlN depositions at 675 °C result in epitaxial Ti2AlN growth with basal planes parallel to the substrate surface. Nominal 4TiAl3N depositions at 675 °C and above, however, yield TiN and Ti2AlN domains due to Al loss to the vacuum. Depositions at a lower temperature of 600 °C yield films with correct 4:1:3 stoichiometry, but Ti4AlN3 formation is supposedly prevented by insufficient adatom mobility. Instead, an incoherent Tin+1AlNn structure with random twinned stacking sequences n is obtained, that exhibits both basal plane orientations parallel as well as nearly perpendicular to the substrate interface. X‑ray photoemission spectroscopy shows that in contrast to stoichiometric nitrides the Al is metallically bonded and hence acts as twinning plane within the Tin+1AlNn stackings. Domains with perpendicular basal plane orientation overgrowth those with parallel ones in a competitive growth mode. The resulting morphology is a combination of smooth‑surfaced parallel basal plane orientation domains interrupted by repeated facetted hillock-like features with perpendicular basal plane orientation.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17107 (URN)10.1063/1.3208065 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
  • 9.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Reactive Magnetron Sputter Deposition and Characterization of Thin Films from the Ti-Al-N and Sc-Al-N Systems2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This Thesis treats the growth and characterization of ternary transition metal nitride thin films. The aim is to probe deeper into the Ti-Al-N system and to explore the novel Sc-Al-N system. Thin films were epitaxially grown by reactive magnetron sputtering from elemental targets onto single-crystal substrates covered with a seed layer. Elastic recoil detection analysis and Rutherford backscattering spectroscopy were used for compositional analysis and depth profiling. Different x-ray diffraction techniques were employed, ex situ using Cu radiation and in situ during deposition using synchrotron radiation, to identify phases, to obtain information about texture, and to determine the thickness and roughness evolution of layers during and after growth. Transmission electron microscopy was used for overview and lattice imaging, and to obtain lattice structure information by electron diffraction. Film properties were determined using van der Pauw measurements of the electrical resistivity, and nanoindentation for the materials hardness and elastic modulus. The epitaxial Mn+1AXn phase Ti2AlN was synthesized by solid-state reaction during interdiffusion between sequentially deposited layers of (0001)-oriented AlN and Ti thin films. When annealing the sample, N and Al diffused into the Ti, forming Ti3AlN at 400 ºC and Ti2AlN at 500 ºC. The Ti2AlN formation temperature is 175 ºC lower than earlier reported results. Ti4AlN3 thin films were, however, not possible to synthesize when depositing films with a Ti:Al:N ratios of 4:1:3. Substrate temperatures at 600 ºC yielded an irregularly stacked Tin+1AlNn layered structure because of the low mobility of Al adatoms. An increased temperature led, however, to an Al deficiency due to an out diffusion of Al atoms, and formation of Ti2AlN phase and Ti1-xAlxN cubic solid solution. In the Sc-Al-N system the first ternary phase was discovered, namely the perovskite Sc3AlN, with a unit cell of 4.40 Å. Its existence was supported by ab initio calculations of the enthalpy showing that Sc3AlN is thermodynamically stable with respect to the binaries. Sc3AlN thin films were experimentally found to have a hardness of 14.2 GPa, an elastic modulus of 21 GPa, and a room temperature resistivity of 41.2 μΩcm.

    List of papers
    1. Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films
    Open this publication in new window or tab >>Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films
    Show others...
    2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 174106Article in journal (Refereed) Published
    Abstract [en]

    The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and α-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3(0001) at 200 °C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400 °C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500 °C resulted in a phase transformation into Ti2AlN(0001) after only 5 min.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17105 (URN)10.1063/1.2731520 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    2. The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti-Al-N thin films
    Open this publication in new window or tab >>The influence of substrate temperature and Al mobility on the microstructural evolution of magnetron sputtered ternary Ti-Al-N thin films
    Show others...
    2009 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 6, p. 064915-Article in journal (Refereed) Published
    Abstract [en]

    Ternary Ti-Al-N films were deposited onto Al2O3 (0001) substrates by reactive co‑sputtering from elemental Ti and Al targets and analyzed by in situ and ex situ x-ray scattering, Rutherford backscattering spectroscopy, transmission electron microscopy and x-ray photoemission spectroscopy. The deposition parameters were set to values that yield Ti:Al:N ratios of 2:1:1 and 4:1:3 at room temperature. 2TiAlN depositions at 675 °C result in epitaxial Ti2AlN growth with basal planes parallel to the substrate surface. Nominal 4TiAl3N depositions at 675 °C and above, however, yield TiN and Ti2AlN domains due to Al loss to the vacuum. Depositions at a lower temperature of 600 °C yield films with correct 4:1:3 stoichiometry, but Ti4AlN3 formation is supposedly prevented by insufficient adatom mobility. Instead, an incoherent Tin+1AlNn structure with random twinned stacking sequences n is obtained, that exhibits both basal plane orientations parallel as well as nearly perpendicular to the substrate interface. X‑ray photoemission spectroscopy shows that in contrast to stoichiometric nitrides the Al is metallically bonded and hence acts as twinning plane within the Tin+1AlNn stackings. Domains with perpendicular basal plane orientation overgrowth those with parallel ones in a competitive growth mode. The resulting morphology is a combination of smooth‑surfaced parallel basal plane orientation domains interrupted by repeated facetted hillock-like features with perpendicular basal plane orientation.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17107 (URN)10.1063/1.3208065 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
    3. Sc3AlN: A New Perovskite
    Open this publication in new window or tab >>Sc3AlN: A New Perovskite
    Show others...
    2008 (English)In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2008, no 8, p. 1193-1195Article in journal (Refereed) Published
    Abstract [en]

    Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc–Al–N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 μm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a roomtemperature electrical resistivity of 41.2 μΩ cm.

    Keywords
    Crystal growth, Density functional theory, Electron microscopy, Perovskite nitride phases, Thin films
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-17106 (URN)10.1002/ejic.200701356 (DOI)
    Available from: 2009-04-14 Created: 2009-03-06 Last updated: 2017-12-13Bibliographically approved
  • 10.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Baehtz, Carsten
    Structural Diagnostics Division, Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf e.V., P.O. Box 510119, D-01314 Dresden, Germany.
    Czigány, Zsolt
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
    Jensen, Jens
    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.
    Effects of volume mismatch and electronic structure on the decomposition of ScAlN and TiAlN solid solutions2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, no 22, p. 224101-Article in journal (Refereed)
    Abstract [en]

    Thin solid films of metastable rocksalt structure (c-) Sc1-xAlxN and Ti1-xAlxN were employed as model systems to investigate the relative influence of volume mismatch and electronic structure driving forces for phase separation. Reactive dual magnetron sputtering was used to deposit stoichiometric Sc0.57Al0.43N(111) and Ti0.51Al0.49N(111) thin films, at 675 °C and 600 °C, respectively, followed by stepwise annealing to a maximum temperature of 1100 °C. Phase transformations during growth and annealing were followed in situ using X-ray scattering. The results show that the as-deposited Sc0.57Al0.43N films phase separate at 1000 °C – 1100 °C into non-isostructural c-ScN and wurtzite-structure (w-) AlN, via nucleation and growth at domain boundaries. Ti0.51Al0.49N, however, exhibits spinodal decomposition into isostructural coherent c-TiN and c-AlN, in the temperature interval of 800 °C – 1000 °C. X-ray pole figures show the coherency between c-ScN and w-AlN, with AlN(0001) || ScN(001) and AlN<01ɸ10> || ScN<1ɸ10>. First principles calculations of mixing energy-lattice spacing curves explain the results on a fundamental physics level and open a route for design of novel metastable pseudobinary phases for hard coatings and electronic materials.

  • 11.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. European Spallat Source ESS AB, Sweden.
    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.
    Jensen, 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.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, R.
    European Spallat Source ESS AB, Sweden; Mid Sweden University, Sweden.
    Growth and oxidization stability of cubic Zr1-xGdxN solid solution thin films2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 19, p. 195301-Article in journal (Refereed)
    Abstract [en]

    We report Zr1-xGdxN thin films deposited by magnetron sputter deposition. We show a solid solubility of the highly neutron absorbing GdN into ZrN along the whole compositional range, which is in excellent agreement with our recent predictions by first-principles calculations. An oxidization study in air shows that Zr1-xGdxN with x reaching from 1 to close to 0 fully oxidizes, but that the oxidization is slowed down by an increased amount of ZrN or stopped by applying a capping layer of ZrN. The crystalline quality of Zr0.5Gd0.5N films increases with substrate temperatures increasing from 100 degrees C to 900 degrees C.

  • 12.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Bareno, Javier
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Czigany, Zsolt
    Hungarian Acadamy of Science.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Cubic Sc1-xAlxN solid solution thin films deposited by reactive magnetron sputter epitaxy onto ScN(111)2009In: JOURNAL OF APPLIED PHYSICS, ISSN 0021-8979, Vol. 105, no 11, p. 132862-Article in journal (Refereed)
    Abstract [en]

    Reactive magnetron sputter epitaxy was used to deposit thin solid films of Sc1-xAlxN (0 andlt;= x andlt;= 1) onto MgO(111) substrates with ScN(111) seed layers. Stoichiometric films were deposited from elemental Sc and Al targets at substrate temperatures of 600 S C. The films were analyzed by Rutherford backscattering spectroscopy, elastic recoil detection analysis, x-ray diffraction, and transmission electron microscopy. Results show that rocksalt structure (c)-Sc1-xAlxN solid solutions with AlN molar fractions up to similar to 60% can be synthesized. For higher AlN contents, the system phase separates into c- and wurtzite structure (w)-Sc1-xAlxN domains. The w-domains are present in three different orientations relative to the seed layer, namely, Sc1-xAlxN(0001)parallel to ScN(111) with Sc1-xAlxN[(1) over bar2 (1) over bar0]parallel to ScN[1 (1) over bar0], Sc1-xAlxN(10 (1) over bar1)parallel to ScN(111) with Sc1-xAlxN[(1) over bar2 (1) over bar0]parallel to ScN[1 (1) over bar0], and Sc1-xAlxN(10 (1) over bar1)parallel to ScN(113). The results are compared to first-principles density functional theory calculations for the mixing enthalpies of c-, w-, and zinc blende Sc0.50Al0.50N solid solutions, yielding metastability with respect to phase separation for all temperatures below the melting points of AlN and ScN.

  • 13.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Schell, Norbert
    GKSS Research Center Geesthacht.
    Borany, J.v.
    Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresen-Rossendorf.
    Birch, Jens
    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.
    Topotaxial growth of Ti2AlN by solid state reaction in AlN/Ti(0001) multilayer thin films2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 90, no 174106Article in journal (Refereed)
    Abstract [en]

    The formation of Ti2AlN by solid state reaction between layers of wurtzite-AlN and α-Ti was characterized by in situ x-ray scattering. The sequential deposition of these layers by dual magnetron sputtering onto Al2O3(0001) at 200 °C yielded smooth, heteroepitaxial (0001) oriented films, with abrupt AlN/Ti interfaces as shown by x-ray reflectivity and Rutherford backscattering spectroscopy. Annealing at 400 °C led to AlN decomposition and diffusion of released Al and N into the Ti layers, with formation of Ti3AlN. Further annealing at 500 °C resulted in a phase transformation into Ti2AlN(0001) after only 5 min.

  • 14.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Bareño, Javier
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Czigány, Zsolt
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Zukauskaite, Agne
    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.
    Wurtzite-structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: structural characterization and first-principles calculations2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, no 12, p. 123515-Article in journal (Refereed)
    Abstract [en]

    AlN(0001) was alloyed with ScN with molar fractions up to ~22%, while retaining a singlecrystal wurtzite (w-) structure and with lattice parameters matching calculated values. Material synthesis was realized by magnetron sputter epitaxy of thin films starting from optimal conditions for the formation of w-AlN onto lattice-matched w-AlN seed layers on Al2O3(0001) and MgO(111) substrates. Films with ScN contents between 23% and ~50% exhibit phase separation into nanocrystalline ScN and AlN, while ScN-rich growth conditions yield a transformation to rocksalt-structure Sc1-xAlxN(111) films. The experimental results are analyzed with ion beam analysis, X-ray diffraction, and transmission electron microscopy, together with ab-initio calculations of mixing enthalpies and lattice parameters of solid solutions in wurtzite, rocksalt, and layered hexagonal phases.

  • 15.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Andersen, Ken
    European Spallat Source ESS AB, Sweden .
    Bigault, Thierry
    Institute Max Von Laue Paul Langevin, France .
    Buffet, Jean-Claude
    Institute Max Von Laue Paul Langevin, France .
    Correa, Jonathan
    Institute Max Von Laue Paul Langevin, France .
    van Esch, Patrick
    Institute Max Von Laue Paul Langevin, France .
    Guerard, Bruno
    Institute Max Von Laue Paul Langevin, France .
    Hall-Wilton, Richard
    European Spallat Source ESS AB, Sweden .
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Khaplanov, Anton
    European Spallat Source ESS AB, Sweden Institute Max Von Laue Paul Langevin, France .
    Piscitelli, Francesco
    Institute Max Von Laue Paul Langevin, France .
    Vettier, Christian
    European Spallat Source ESS AB, Sweden European Synchrotron Radiat Facil, France .
    Vollenberg, Wilhelmus
    CERN, Switzerland .
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    B4C thin films for neutron detection2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 10, p. 104908-Article in journal (Refereed)
    Abstract [en]

    Due to the very limited availability of He-3, new kinds of neutron detectors, not based on 3He, are urgently needed. Here, we present a method to produce thin films of (B4C)-B-10, with maximized detection efficiency, intended to be part of a new generation of large area neutron detectors. B4C thin Films have been deposited onto Al-blade and Si wafer substrates by dc magnetron sputtering from (B4C)-B-nat and (B4C)-B-10 targets in an Ar discharge, using an industrial deposition system. The films were characterized with scanning electron microscopy, elastic recoil detection analysis, x-ray reflectivity, and neutron radiography. We show that the film-substrate adhesion and film purity are improved by increased substrate temperature and deposition rate. A deposition rate of 3.8 angstrom/s and substrate temperature of 400 degrees C result in films with a density close to bulk values and good adhesion to film thickness above 3 mu m. Boron-10 contents of almost 80 at. % are obtained in 6.3 m(2) of 1 mu m thick (B4C)-B-10 thin films coated on Al-blades. Initial neutron absorption measurements agree with Monte Carlo simulations and show that the layer thickness, number of layers, neutron wavelength, and amount of impurities are determining factors. The study also shows the importance of having uniform layer thicknesses over large areas, which for a full-scale detector could be in total similar to 1000 m(2) of two-side coated Al-blades with similar to 1 mu m thick (B4C)-B-10 films.

  • 16.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Beckers, Manfred
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics . Linköping University, The Institute of Technology.
    Czigany, Zsolt
    Research Institute for Technical Physics and Materials Science, Hungarian Academy of Sciences, P.O. Box 49, H-1525 Budapest, Hungary .
    Mücklich, Arndt
    Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sc3AlN: A New Perovskite2008In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2008, no 8, p. 1193-1195Article in journal (Refereed)
    Abstract [en]

    Sc3AlN with perovskite structure has been synthesized as the first ternary phase in the Sc–Al–N system. Magnetron sputter epitaxy at 650 °C was used to grow single-crystal, stoichiometric Sc3AlN(111) thin films onto MgO(111) substrates with ScN(111) seed layers as shown by elastic recoil detection analysis, X-ray diffraction, and transmission electron microscopy. The Sc3AlN phase has a lattice parameter of 4.40 Å, which is in good agreement with the theoretically predicted 4.42 Å. Comparisons of total formation energies show that Sc3AlN is thermodynamically stable with respect to all known binary compounds. Sc3AlN(111) films of 1.75 μm thickness exhibit a nanoindentation hardness of 14.2 GPa, an elastic modulus of 249 GPa, and a roomtemperature electrical resistivity of 41.2 μΩ cm.

  • 17.
    Höglund, Carina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. European Spallat Source ESS AB, Sweden.
    Zeitelhack, Karl
    Technical University of Munich, Germany.
    Kudejova, Petra
    Technical University of Munich, Germany.
    Jensen, Jens
    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.
    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.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, Richard
    European Spallat Source ESS AB, Sweden; Mid Sweden University, Sweden.
    Stability of (B4C)-B-10 thin films under neutron radiation2015In: Radiation Physics and Chemistry, ISSN 0969-806X, E-ISSN 1879-0895, Vol. 113, p. 14-19Article in journal (Refereed)
    Abstract [en]

    Thin films of (B4C)-B-10 have shown to be very suitable as neutron-converting material in the next generation of neutron detectors, replacing the previous predominantly used He-3. In this contribution we show under realistic conditions that (B4C)-B-10 films are not damaged by the neutron irradiation and interactions, which they will be exposed to under many years in a neutron detector. 1 mu m thick (B4C)-B-10 thin films were deposited onto Al or Si substrates using dc magnetron sputtering. As-deposited films were exposed to a cold neutron beam with fluences of up to 1.1 x 10(14) cm(-2) and a mean wavelength of 6.9 angstrom. Both irradiated and as-deposited reference samples were characterized with time-of-flight elastic recoil detection analysis, scanning electron microscopy, transmission electron microscopy, X-ray photoemission spectroscopy, and X-ray diffraction. We show that only 1.8 ppm of the B-10 atoms were consumed and that the film composition does not change by the neutron interaction within the measurement accuracy. The irradiation does not deteriorate the film adhesion and there is no indication that it results in increased residual stress values of the as-deposited films of 0.095 GPa. From what is visible with the naked eye and down to atomic level studies, no change from the irradiation could be found using the above-mentioned characterization techniques.

  • 18.
    Imam, Mewlude
    et al.
    Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. European Spallat Source ESS AB, Sweden.
    Gaul, Konstantin
    University of Marburg, Germany; University of Marburg, Germany.
    Stegmueller, Andreas
    University of Marburg, Germany; University of Marburg, Germany.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. European Spallat Source ESS AB, Sweden.
    Jensen, 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.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tonner, Ralf
    University of Marburg, Germany; University of Marburg, Germany.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Gas phase chemical vapor deposition chemistry of triethylboron probed by boron-carbon thin film deposition and quantum chemical calculations2015In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 3, no 41, p. 10898-10906Article in journal (Refereed)
    Abstract [en]

    We present triethylboron (TEB) as a single-source precursor for chemical vapor deposition (CVD) of BxC thin films and study its gas phase chemistry under CVD conditions by quantum chemical calculations. A comprehensive thermochemical catalogue for the species of the gas phase chemistry of TEB is examined and found to be dominated by beta-hydride eliminations of C2H4 to yield BH3. A complementary bimolecular reaction path based on H-2 assisted C2H6 elimination to BH3 is also significant at lower temperatures in the presence of hydrogen. Furthermore, we find a temperature window of 600-1000 degrees C for the deposition of X-ray amorphous BxC films with 2.5 less than= x less than= 4.5 from TEB. Films grown at temperatures below 600 degrees C contain high amounts of H, while temperatures above 1000 degrees C result in C-rich films. The film density and hardness are determined to be in the range of 2.40-2.65 g cm(-3) and 29-39 GPa, respectively, within the determined temperature window.

  • 19.
    Imam, Mewlude
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallat Source ESS AB, Sweden.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. European Spallation Source ERIC, Lund, Sweden.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallation Source ERIC, Lund, Sweden.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, Richard
    European Spallation Source ERIC, Lund, Sweden.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Pedersen, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, Faculty of Science & Engineering.
    Trimethylboron as single-source precursor for boron-carbonthin film synthesis by plasma chemical vapor deposition2015Manuscript (preprint) (Other academic)
    Abstract [en]

    Boron-carbon (BxC) thin films are potential neutron converting layers for 10B-based neutron detectors. However, as common material choices for such detectors do not tolerate temperature above 500°C, a low temperature deposition route is required for this application. Here we study trimethylboron B(CH3)3 (TMB) as a single-source precursor for the deposition of BxC thin films by plasma CVD using Ar plasma. The effect of plasma power, TMB/Ar ratio and total pressure on the film composition, morphology and structure are investigated. The highest B/C ratio of 1.9 was achieved at high TMB flow in a low total pressure and high plasma power which rendered an approximate substrate temperature of ~ 300 °C. X-ray photoelectron spectroscopy shows that B-C bonds prevail in the films, although C-C and B-O bonds are also present. Raman spectroscopy confirms the presence of amorphous carbon phases in the films. The H content in the films is found to be 15±5 at. % by the time of flight elastic recoil detection analysis (Tof-ERDA). The film density as determined from X-ray reflectivity (XRR) measurements is 2. 16 ± 0.01  g/cm3 and the internal compressive stresses are measured to be less than 400 MPa.

  • 20.
    Khatibi, Ali
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eriksson, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O. Å.
    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.
    Birch, 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.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Face-Centered Cubic (Al1-xCrx)2O32011In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 8, p. 2426-2429Article in journal (Refereed)
    Abstract [en]

    We report the discovery of a face-centered cubic (Al1−xCrx)2O3 solid solution [0.60bxb0.70] in films grownonto Si substrates using reactive radio frequency magnetron sputtering from Al and Cr targets at 400 °C. Theproposed structure is NaCl-like with 33% vacancies on the metal sites. The unit cell parameter is 4.04 Å asdetermined by X-ray diffraction. The films have a b100N preferred crystallographic orientation and exhibithardness values up to 26 GPa and an elastic modulus of 220–235 GPa.

  • 21.
    Magnuson, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mattesini, M.
    Universidad Complutense de Madrid.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    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.
    Electronic structure and chemical bonding anisotropy investigation of wurtzite AlN2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 80, p. 155105-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and the anisotropy of the Al - N p and s chemical bonding of wurtzite AlN has been investigated by bulk-sensitive total fluorescence yield absorption and soft x-ray emission spectroscopies. The measured N K, Al L1, and Al L2,3 x-ray emission and N 1s x-ray absorption spectra are compared with calculated spectra using first principles density-functional theory including dipole transition matrix elements. The main N 2p - Al 3p hybridization regions are identified at -1.0 to -1.8 eV and -5.0 to -5.5 eV below the top of the valence band. In addition, N 2s - Al 3p and N 2s - Al 3s hybridization regions are found at the bottom of the valence band around -13.5 eV and -15 eV, respectively. A strongly modified spectral shape of Al 3s states in the Al L2,3 emission from AlN in comparison to Al metal is found, which is also reflected in the N 2p - Al 3p hybridization observed in the Al L1 emission. The differences between the electronic structure and chemical bonding of AlN and Al metal are discussed in relation to the position of the hybridization regions and the valence band edge influencing the magnitude of the large band gap.

  • 22.
    Magnuson, Martin
    et al.
    Uppsala University.
    Mattesini, M.
    Departamento de Física de la Tierra, Astronomía y Astrofísica I, Universidad Complutense de Madrid.
    Li, S.
    Uppsala University.
    Höglund, Carina
    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.
    Eriksson, O.
    Uppsala University.
    Bonding mechanism in the nitrides Ti2AlN and TiN: An experimental and theoretical investigation2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 195127Article in journal (Refereed)
    Abstract [en]

    Theelectronic structure of nanolaminate Ti2AlN and TiN thin films hasbeen investigated by bulk-sensitive soft x-ray emission spectroscopy. The measuredTi L2,3, N K, Al L1, and Al L2,3 emissionspectra are compared with calculated spectra using ab initio density-functionaltheory including dipole transition-matrix elements. Three different types of bondregions are identified; a relatively weak Ti  3d-Al  3p bonding between −1and −2  eV below the Fermi level, and Ti  3d-N  2p and Ti  3d-N  2sbondings which are deeper in energy observed at −4.8  eV and−15  eV below the Fermi level, respectively. A strongly modified spectralshape of 3s states of Al L2,3 emission from Ti2AlNin comparison with pure Al metal is found, which reflectsthe Ti  3d-Al  3p hybridization observed in the Al L1 emission. Thedifferences between the electronic and crystal structures of Ti2AlN andTiN are discussed in relation to the intercalated Al layersof the former compound and the change of the materialsproperties in comparison with the isostructural carbides.

  • 23.
    Magnuson, Martin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Mattesini, Maurizio
    University Complutense Madrid.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    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.
    Electronic structure investigation of the cubic inverse perovskite Sc3AlN2008In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 78, no 23, p. 235102-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of the recently discovered inverse perovskite Sc3AlN, in comparison to those of ScN and Sc metal, have been investigated by bulk-sensitive soft-x-ray emission spectroscopy. The measured Sc L, N K, Al L-1, and Al L-2,L-3 emission spectra are compared with calculated spectra using first-principles density-functional theory including dipole transition-matrix elements. The main Sc 3d-N 2p and Sc 3d-Al 3p chemical bond regions are identified at -4 and -1.4 eV below the Fermi level, respectively. A strongly modified spectral shape of 3s states in the Al L-2,L-3 emission from Sc3AlN in comparison to that for pure Al metal is found, which reflects the Sc 3d-Al 3p hybridization observed in the Al L-1 emission. The differences between the electronic structures of Sc3AlN, ScN, and Sc metal are discussed in relation to the change in the conductivity and elastic properties.

  • 24.
    Magnuson, Martin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Mattesini, Maurizio
    Universidad Complutense de Madrid.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    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.
    Electronic structure of GaN and Ga investigated by soft x-ray spectroscopy and first-principles methods2010In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 81, p. 085125-Article in journal (Refereed)
    Abstract [en]

    The electronic structure and chemical bonding of wurtzite-GaN investigated by N 1s soft x-ray absorption spectroscopy and N K, Ga M1, and Ga M2,3 emission spectroscopy is compared to that of pure Ga. The measurements are interpreted by calculated spectra using first-principles density-functional theory (DFT) including dipole transition matrix elements and additional on-site Coulomb interaction (WC-GGA+U). The Ga 4p-N 2p and Ga 4s-N 2p hybridization and chemical bond regions are identified at the top of the valence band between −1.0 and −2.0 and further down between −5.5 and −6.5 eV, respectively. In addition, N 2s-N 2p-Ga 4s and N 2s-N 2p-Ga 3d hybridization regions occur at the bottom of the valence band between −13 and −15 eV, and between −17.0 and −18.0 eV, respectively. A bandlike satellite feature is also found around −10 eV in the Ga M1 and Ga M2,3 emission from GaN, but is absent in pure Ga and the calculated ground-state spectra. The difference between the identified spectroscopic features of GaN and Ga are discussed in relation to the various hybridization regions calculated within band-structure methods.

  • 25.
    Mattesini, Maurizio
    et al.
    Universidad Complutense de Madrid.
    Magnuson, Martin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Abrikosov, Igor A.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical 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.
    Elastic properties and electrostructural correlations in ternary scandium-based cubic inverse perovskites: A first-principles study2009In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 125122Article in journal (Refereed)
    Abstract [en]

    Wehave performed ab initio calculations for the cubic inverse-perovskite Sc3EN(E=Al,Ga,In) systems to study their electronic band-structures and elastic properties.In this study, we used the accurate augmented plane waveplus local orbital method to find the equilibrium structural parametersand to compute the full elastic tensors. The obtained single-crystalelastic constants were used to quantify the stiffness of theSc-based ternary nitrides and to appraise their mechanical stability. Thesite-projected density of states, Fermi surfaces, and the charge-density plotshave also been used to analyze the chemical bonding betweenthe Sc6N cluster and the surrounding metallic lattice of eitherAl, Ga, or In atoms. Our calculations show that Sc3GaNhas the largest covalent Sc-N bonding-type character with the highestYoung, shear, and bulk moduli. Compared with the other twoisoelectronic systems, it also behaves as the most brittle materialwith a relatively large elastic anisotropy.

  • 26.
    Mikhaylushkin, Arkady
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Czigany, Zs
    Hungarian Acadamy of Science.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Stability of the ternary perovskites Sc3EN (E=B,Al,Ga,In) from first principles2009In: PHYSICAL REVIEW B, ISSN 1098-0121, Vol. 79, no 13, p. 134107-Article in journal (Refereed)
    Abstract [en]

    Mechanical and thermodynamic stability of the isoelectronic ternary inverse perovskites Sc3EN (E=B,Al,Ga,In) has been studied from first principles. We confirm stability of recently synthesized cubic phases Sc3AlN and Sc3InN, and predict the stability of cubic Sc3GaN and a triclinic phase aP20-Sc3BN. Substantial phonon softening in Sc3AlN and Sc3GaN is observed indicating a possibility that structural defects could form readily. In accord, our experiments show that magnetron sputter deposited films contain regions with high density of nonperiodic stacking faults along the < 111 > growth direction. We suggest that defect-free crystals may exhibit anomalies in the carrier properties, promising for electronic applications.

  • 27.
    Muraro, A.
    et al.
    IFP CNR, Italy.
    Albani, G.
    University of Milano Bicocca, Italy.
    Perelli Cippo, E.
    IFP CNR, Italy.
    Croci, G.
    University of Milano Bicocca, Italy.
    Angella, G.
    IENI CNR, Italy.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Cazzaniga, C.
    STFC, England.
    Caniello, R.
    IFP CNR, Italy.
    DellEra, F.
    IFP CNR, Italy.
    Ghezzi, F.
    IFP CNR, Italy.
    Grosso, G.
    IFP CNR, Italy.
    Hall-Wilton, R.
    European Spallat Source ESS ERIC, Sweden.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. 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.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Robinson, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rebai, M.
    University of Milano Bicocca, Italy.
    Salvato, G.
    IPCF CNR, Italy.
    Tresoldi, D.
    IPCF CNR, Italy.
    Vasi, C.
    IPCF CNR, Italy.
    Tardocchi, M.
    IFP CNR, Italy.
    Neutron radiography as a non-destructive method for diagnosing neutron converters for advanced thermal neutron detectors2016In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 11, no C03033Article in journal (Refereed)
    Abstract [en]

    Due to the well-known problem of He-3 shortage, a series of different thermal neutron detectors alternative to helium tubes are being developed, with the goal to find valid candidates for detection systems for the future spallation neutron sources such as the European Spallation Source (ESS). A possible He-3-free detector candidate is a charged particle detector equipped with a three dimensional neutron converter cathode (3D-C). The 3D-C currently under development is composed by a series of alumina (Al2O3) lamellas coated by 1 mu m of B-10 enriched boron carbide (B4C). In order to obtain a good characterization in terms of detector efficiency and uniformity it is crucial to know the thickness, the uniformity and the atomic composition of the B4C neutron converter coating. In this work a non-destructive technique for the characterization of the lamellas that will compose the 3D-C was performed using neutron radiography. The results of these measurements show that the lamellas that will be used have coating uniformity suitable for detector applications. This technique (compared with SEM, EDX, ERDA, XPS) has the advantage of being global (i.e. non point-like) and non-destructive, thus it is suitable as a check method for mass production of the 3D-C elements.

  • 28.
    Pedersen, Henrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    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.
    Henry, Anne
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Low Temperature CVD of Thin, Amorphous Boron-Carbon Films for Neutron Detectors2012In: Chemical Vapor Deposition, ISSN 0948-1907, E-ISSN 1521-3862, Vol. 18, no 7-9, p. 221-224Article in journal (Refereed)
    Abstract [en]

    Thin, amorphous boron-carbon films are deposited at low temperature (400600?degrees C) by thermally activated CVD using the organoborane triethylboron (TEB) as a single precursor. Two different carrier gases are tested. At 600?degrees C, using argon as the carrier gas, the deposition rate is close to 1?mu m h-1. The film has a density of 2.14?g?cm-3 with a B/C ratio of 3.7. When hydrogen is used as the carrier gas, the film density is 2.42?g?cm-3, the B/C ratio 4.6, and the deposition rate 0.35?mu m h-1. The hydrogen content in the films is about 34 at.-%, regardless of ambient conditions during deposition, and varies only with the deposition temperature. In addition, both the film composition and the film density are found to vary significantly with the deposition temperature and the atmospheric conditions. Based upon these results, a deposition mechanism for the growth of boron-carbon films from TEB, where the TEB molecule is decomposed to BH3 and hydrocarbons, is suggested.

  • 29.
    Persson, P. O. Å.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    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.
    Ti2Al(O,N) formation by solid state reaction between substoichiometric TiN thin films and Al2O3(0001) substrates2011In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 519, no 8, p. 2421-2425Article in journal (Refereed)
    Abstract [en]

    Titanium nitride TiNx (0.1 ≤ x ≤ 1) thin films were deposited onto Al2O3(0001) substrates using reactive magnetron sputtering at substrate temperatures (Ts) ranging from 800 ºC to 1000 ºC and N2 partial pressures (pN2) between 0.1 and 1.0 mTorr. It is found that Al and O from the substrates diffuse into the substoichiometric TiNx films during deposition. Solid state reactions between the film and substrate result in the formation of Ti2O and Ti3Al domains at low N2 partial pressures, while for increasing pN2, the Ti2AlN MAX phase nucleates and grows together with TiNx. Depositions at increasingly stoichiometric conditions result in a decreasing incorporation of the substrate species into the growing film. Eventually, a stoichiometric deposition gives a stable TiN(111) || Al2O3(0001) structure without the incorporation of substrate species. Growth at Ts 1000 ºC yields Ti2AlN(0001), leading to a reduced incorporation of substrate species compared to films grown at 900 ºC, but contains also Ti2AlN(101ɸ3) grains. Finally, the Ti2AlN domains incorporate O, likely on the N site, such that a MAX phase oxynitride Ti2Al(O,N) is formed. The results were obtained by a combination of structural methods, including X-ray diffraction (XRD) and (scanning) transmission electron microscopy ((S)TEM), together with spectroscopy methods, which comprise elastic recoil detection analysis (ERDA), energy dispersive X-ray spectroscopy (EDX), and electron energy loss spectroscopy (EELS).

  • 30.
    Persson, P.O.A.
    et al.
    Persson, P.O.Å., School of Physics, University of Sydney, NSW 2006, Australia.
    Rosen, Johanna
    School of Physics, University of Sydney, NSW 2006, Australia.
    McKenzie, D.R.
    School of Physics, University of Sydney, NSW 2006, Australia.
    Bilek, M.M.M.
    School of Physics, University of Sydney, NSW 2006, Australia.
    Höglund, Carina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    A solid phase reaction between Ti Cx thin films and Al2 O3 substrates2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 6Article in journal (Refereed)
    Abstract [en]

    Ti Cx thin films were deposited on Al2 O3 substrates at 900 °C by using a multiple cathode high current pulsed cathodic arc. The Ti:C pulse ratio and, hence, the composition was varied from C rich to Ti rich. It is found that the Al2 O3 substrate is decomposed and reacts with the Ti Cx film to incorporate significant amounts of O and Al in the growing film. When the stoichiometry is suitable, epitaxially oriented Ti2 AlC MAX phase with significant O incorporated is formed. The results indicate that Al2 O3 is not an ideal substrate material for the growth of transition metal carbides and MAX phase thin films. © 2008 American Institute of Physics.

  • 31.
    Pfeiffer, D.
    et al.
    European Spallat Source ESS AB, Sweden; CERN, Switzerland.
    Resnati, F.
    European Spallat Source ESS AB, Sweden; CERN, Switzerland.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Etxegarai, M.
    European Spallat Source ESS AB, Sweden.
    Hall-Wilton, R.
    European Spallat Source ESS AB, Sweden; Mid Sweden University, Sweden.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. European Spallat Source ESS AB, Sweden.
    Hultman, L.
    Mid Sweden University, Sweden.
    Llamas-Jansa, I.
    European Spallat Source ESS AB, Sweden; Institute Energy Technology IFE, Norway.
    Oliveri, E.
    CERN, Switzerland.
    Oksanen, E.
    European Spallat Source ESS AB, Sweden.
    Robinson, L.
    European Spallat Source ESS AB, Sweden.
    Ropelewski, L.
    CERN, Switzerland.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallat Source ESS AB, Sweden.
    Streli, C.
    Vienna University of Technology, Austria.
    Thuiner, P.
    CERN, Switzerland; Vienna University of Technology, Austria.
    First measurements with new high-resolution gadolinium-GEM neutron detectors2016In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 11, no P05011Article in journal (Refereed)
    Abstract [en]

    European Spallation Source instruments like the macromolecular diffractometer (NMX) require an excellent neutron detection efficiency, high-rate capabilities, time resolution, and an unprecedented spatial resolution in the order of a few hundred micrometers over a wide angular range of the incoming neutrons. For these instruments solid converters in combination with Micro Pattern Gaseous Detectors (MPGDs) are a promising option. A GEM detector with gadolinium converter was tested on a cold neutron beam at the IFE research reactor in Norway. The mu TPC analysis, proven to improve the spatial resolution in the case of B-10 converters, is extended to gadolinium based detectors. For the first time, a Gd-GEM was successfully operated to detect neutrons with a measured efficiency of 11.8% at a wavelength of 2 angstrom and a position resolution better than 250 mu m.

  • 32.
    Pfeiffer, D.
    et al.
    European Spallat Source ESS AB, Sweden; CERN, Switzerland.
    Resnati, F.
    European Spallat Source ESS AB, Sweden; CERN, Switzerland.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hall-Wilton, R.
    European Spallat Source ESS AB, Sweden; Mid Sweden University, Sweden.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. European Spallat Source ESS AB, Sweden.
    Hultman, L.
    Mid Sweden University, Sweden.
    Iakovidis, G.
    CERN, Switzerland; Brookhaven National Lab, NY 11973 USA.
    Oliveri, E.
    CERN, Switzerland.
    Oksanen, E.
    European Spallat Source ESS AB, Sweden.
    Ropelewski, L.
    CERN, Switzerland.
    Thuiner, P.
    CERN, Switzerland; Vienna University of Technology, Austria.
    The mu TPC method: improving the position resolution of neutron detectors based on MPGDs2015In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 10, no P04004Article in journal (Refereed)
    Abstract [en]

    Due to the He-3 crisis, alternatives to the standard neutron detection techniques are becoming urgent. In addition, the instruments of the European Spallation Source (ESS) require advances in the state of the art of neutron detection. The instruments need detectors with excellent neutron detection efficiency, high rate capabilities and unprecedented spatial resolution. The Macromolecular Crystallography instrument (NMX) requires a position resolution in the order of 200 mu m over a wide angular range of incoming neutrons. Solid converters in combination with Micro Pattern Gaseous Detectors (MPGDs) are proposed to meet the new requirements. Charged particles rising from the neutron capture have usually ranges larger than several millimetres in gas. This is apparently in contrast with the requirements for the position resolution. In this paper, we present an analysis technique, new in the field of neutron detection, based on the Time Projection Chamber (TPC) concept. Using a standard Single-GEM with the cathode coated with (B4C)-B-10, we extract the neutron interaction point with a resolution of better than sigma = 200 mu m.

  • 33.
    Piscitelli, F.
    et al.
    European Spallat Source ERIC, Sweden; ILL Grenoble, France; University of Perugia, Italy.
    Khaplanov, A.
    European Spallat Source ERIC, Sweden; ILL Grenoble, France.
    Devishvili, A.
    Ruhr University of Bochum, Germany.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. European Spallat Source ERIC, Sweden.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. European Spallat Source ERIC, Sweden.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Dennison, A. J. C.
    ILL Grenoble, France; Uppsala University, Sweden.
    Gutfreund, P.
    ILL Grenoble, France.
    Hall-Wilton, R.
    European Spallat Source ERIC, Sweden; Mid Sweden University, Sweden.
    Van Esch, P.
    ILL Grenoble, France.
    Neutron reflectometry on highly absorbing films and its application to (B4C)-B-10-based neutron detectors2016In: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences, ISSN 1364-5021, E-ISSN 1471-2946, Vol. 472, no 2185, p. 20150711-Article in journal (Refereed)
    Abstract [en]

    Neutron reflectometry is a powerful tool used for studies of surfaces and interfaces. The absorption in the typical studied materials is neglected and this technique is limited only to the reflectivity measurement. For strongly absorbing nuclei, the absorption can be directly measured by using the neutron-induced fluorescence technique which exploits the prompt particle emission of absorbing isotopes. This technique is emerging from soft matter and biology where highly absorbing nuclei, in very small quantities, are used as a label for buried layers. Nowadays, the importance of absorbing layers is rapidly increasing, partially because of their application in neutron detection; a field that has become more active also due to the He-3-shortage. We extend the neutron-induced fluorescence technique to the study of layers of highly absorbing materials, in particular (B4C)-B-10. The theory of neutron reflectometry is a commonly studied topic; however, when a strong absorption is present the subtle relationship between the reflection and the absorption of neutrons is not widely known. The theory for a general stack of absorbing layers has been developed and compared to measurements. We also report on the requirements that a (B4C)-B-10 layer must fulfil in order to be employed as a converter in neutron detection.

  • 34.
    Stefanescu, I
    et al.
    Technical University of Munich, Germany .
    Abdullahi, Y
    Technical University of Munich, Germany .
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Defendi, I
    Technical University of Munich, Germany .
    Hall-Wilton, R
    European Spallat Source ESS AB, Sweden .
    Höglund, Carina
    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.
    Seiler, D
    Technical University of Munich, Germany .
    Zeitelhack, K
    Technical University of Munich, Germany .
    Development of a novel macrostructured cathode for large-area neutron detectors based on the B-10-containing solid converter2013In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 727, p. 109-125Article in journal (Refereed)
    Abstract [en]

    We present a novel design for a macrostructured cathode that can be coated with a thin layer of the B-10 solid converter and mounted to replace the Boron-lined flat parallel plates of a proportional counter used for slow neutron detection. The proposed design consists of a 3D regular pattern exhibiting millimeter deep grooves with an opening angle of alpha = 45 degrees, which could be created in the substrate material by milling or forming. When a commonly used coating method like magnetron sputtering is employed to deposit the Boron-layer, due to the line-of-sight distribution of the ions, the thickness of the coating on the side of the grooves will be reduced by a factor similar to sin alpha/2 with respect to the thickness of the layer deposited on a flat surface normal to the ion flux. The effective neutron absorption film thickness is in this case similar for the sidewalls of the grooves and a surface at normal incidence, yielding comparable absorption efficiencies. However, the escape efficiency for the reaction products is higher for the sidewalls, owing to the thinner coating. This leads to a higher overall detection efficiency for the grooved cathode when compared to a flat cathode with the same surface area and coated with a Boron layer with roughly the same thickness. In this paper we present and discuss the GEANT4 simulations performed to optimize the geometry of the cathode, the manufacturing and coating by magnetron sputtering, as well as the proof-of-principle measurements carried out in order to assess the performance of the proposed design.

  • 35.
    Tasnadi, Ferenc
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Höglund, Carina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wingqvist, Gunilla
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Birch, Jens
    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.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Origin of the Anomalous Piezoelectric Response in Wurtzite ScxAl1-xN Alloys2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, no 13, p. 137601-Article in journal (Refereed)
    Abstract [en]

    The origin of the anomalous, 400% increase of the piezoelectric coefficient in ScxAl1-xN alloys is revealed. Quantum mechanical calculations show that the effect is intrinsic. It comes from a strong change in the response of the internal atomic coordinates to strain and pronounced softening of C-33 elastic constant. The underlying mechanism is the flattening of the energy landscape due to a competition between the parent wurtzite and the so far experimentally unknown hexagonal phases of the alloy. Our observation provides a route for the design of materials with high piezoelectric response.

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