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  • 1.
    Alami, Jones
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Gudmundsson, J. T.
    University of Iceland, Reykjavik.
    Böhlmark, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating 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.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics . Linköping University, The Institute of Technology.
    Plasma dynamics in a highly ionized pulsed magnetron discharge2005In: Plasma sources science & technology, ISSN 0963-0252, E-ISSN 1361-6595, Vol. 14, no 3, p. 525-531Article in journal (Refereed)
    Abstract [en]

    We report on electrostatic probe measurements of a high-power pulsed magnetron discharge. Space- and time-dependent characteristics of the plasma parameters are obtained as functions of the process parameters. By applying high-power pulses (peak power of ~0.5 MW), with a pulse-on time of ~100 µs and a repetition frequency of 20 ms, peak electron densities of the order of ~1019 m− 3, i.e. three orders of magnitude higher than for a conventional dc magnetron discharge, are achieved soon after the pulse is switched on. At high sputtering gas pressures (>5 mTorr), a second peak occurs in the electron density curve, hundreds of microseconds after the pulse is switched off. This second peak is mainly due to an ion acoustic wave in the plasma, reflecting off the chamber walls. This is concluded from the time delay between the two peaks in the electron and ion saturation currents, which is shown to be dependent on the chamber dimensions and the sputtering gas composition. Finally, the electron temperature is determined, initially very high but decreasing rapidly as the pulse is turned off. The reduction seen in the electron temperature, close to the etched area of the cathode, is due to cooling by the sputtered metal atoms.

  • 2.
    Alves Machado Filho, Manoel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Universidade Maurício de Nassau − UNINASSAU − Unidade Vitória da Conquista, 45020-750Vitória da Conquista, Bahia, Brazil.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    dos Santos, Renato Batista
    Instituto Federal de Educação, Ciência e Tecnologia Baiano, 46880-000Itaberaba, Bahia, Brazil.
    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.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Self-Induced Core–Shell InAlN Nanorods: Formation and Stability Unraveled by Ab Initio Simulations2023In: ACS Nanoscience Au, E-ISSN 2694-2496, Vol. 3, no 1, p. 84-93Article in journal (Refereed)
    Abstract [en]

    By addressing precursor prevalence and energetics using the DFT-based synthetic growth concept (SGC), the formation mechanism of self-induced InAlN core–shell nanorods (NRs) synthesized by reactive magnetron sputter epitaxy (MSE) is explored. The characteristics of In- and Al-containing precursor species are evaluated considering the thermal conditions at a typical NR growth temperature of around 700 °C. The cohesive and dissociation energies of In-containing precursors are consistently lower than those of their Al-containing counterparts, indicating that In-containing precursors are more weakly bonded and more prone to dissociation. Therefore, In-containing species are expected to exhibit lower abundance in the NR growth environment. At increased growth temperatures, the depletion of In-based precursors is even more pronounced. A distinctive imbalance in the incorporation of Al- and In-containing precursor species (namely, AlN/AlN+, AlN2/AlN2+, Al2N2/Al2N2+, and Al2/Al2+ vs InN/InN+, InN2/InN2+, In2N2/In2N2+, and In2/In2+) is found at the growing edge of the NR side surfaces, which correlates well with the experimentally obtained core–shell structure as well as with the distinctive In-rich core and vice versa for the Al-rich shell. The performed modeling indicates that the formation of the core–shell structure is substantially driven by the precursors’ abundance and their preferential bonding onto the growing edge of the nanoclusters/islands initiated by phase separation from the beginning of the NR growth. The cohesive energies and the band gaps of the NRs show decreasing trends with an increment in the In concentration of the NRs’ core and with an increment in the overall thickness (diameter) of the NRs. These results reveal the energy and electronic reasons behind the limited growth (up to ∼25% of In atoms of all metal atoms, i.e., InxAl1–xN, x ∼ 0.25) in the NR core and may be qualitatively perceived as a limiting factor for the thickness of the grown NRs (typically <50 nm).

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  • 3.
    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.

  • 4.
    Aquila, Andrew L.
    et al.
    Lawrence Berkeley National Laboratory, USA.
    Salmassi, Fahrad
    Lawrence Berkeley National Laboratory, USA.
    Gullikson, Eric M.
    Lawrence Berkeley National Laboratory, USA.
    Eriksson, Fredrik
    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.
    Measurements of the optical constants of scandium in the 50-1300 eV range2004In: SPIE 5538, Optical Constants of Materials for UV to X-Ray Wavelengths / [ed] Regina Soufli, John F. Seely, SPIE - International Society for Optical Engineering, 2004, p. 64-71Conference paper (Refereed)
    Abstract [en]

    Scandium containing multilayers have been produced with very high reflectivity in the soft x-ray spectrum.  Accurate optical constants are required in order to model the multilayer reflectivity.  Since there are relatively few measurements of the optical constants of Scandium in the soft x-ray region we have performed measurements over the energy range of 50-1,300 eV.  Thin films of Scandium were deposited by ion-assisted magnetron sputtering at Linkoping University and DC Magnetron sputtering at CXRO.  Transmission measurements were performed at the Advanced Light Source beamline 6.3.2.  The absorption coefficient was deduced from the measurements and the dispersive part of the index of refraction was obtained using the Kramers-Kronig relation.  The measured optical constants are used to model the near-normal incidence reflectivity of Cr/Sc multilayers near the Sc L2,3 edge.

  • 5.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Berlind, Torun
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . 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.
    Fernández del Río, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Gustafson, Johan
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Biology. Linköping University, The Institute of Technology.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry2012In: AES 2012, Advanced Electromagnetics Symposium, 2012Conference paper (Other academic)
    Abstract [en]

    Polarization effects in reflection from the cuticle of scarab beetles studied by spectroscopic Mueller-matrix ellipsometry

     

    H. Arwin*, T. Berlind, J. Birch, L. Fernandez Del Rio, J. Gustafson, J. Landin,

    R. Magnusson, C. Åkerlind, and K. Järrendahl

    Department of Physics, Chemistry and Biology, Linköping University, Sweden

    *corresponding author: han@ifm.liu.se

     

    Abstract- Many scarab beetles exhibit structural colors and complex polarization phenomena in reflection. These effects are characterized with spectroscopic Mueller-matrix ellipsometry in our work. The polarization ellipse of reflected light as well as the degree of polarization is presented including variations with angle of incidence and wavelength. Emphasis is on beetles showing chiral effects and structural modeling of cuticle nanostructure is discussed.

     

    Background Since one hundred years it is known that some scarab beetles reflect elliptically polarized light as demonstrated by Michelson for the beetle Chrysina resplendens [1]. The handedness of the polarization is in a majority of the cases left-handed but also right-handed polarization has been found [2,3]. The ellipticity varies with wavelength and viewing angle but can be close to +1 or -1 (right or left circular polarization, respectively) and in addition these beetles may exhibit beautiful structural colors. The polarization and color effects are generated in the outer part of the exoskeleton, the cuticle. These natural photonic structures are often multifunctional and play important roles for survival of beetles, e.g. for hiding from or scaring predators, for intraspecies communication, etc. [4]. However, such structures may find use in many commercial applications and a major motivation for detailed studies of natural photonic structures is that they inspire to biomimetic applications [5,6].

    Approach Our objective is to use spectral Mueller-matrix data on scarab beetles to parameterize reflection properties in terms of polarization parameters and degree of polarization. The studied beetles all are phytophagous and include species from the Cetoniinae subfamily (e.g. Cetonia aurata and Coptomia laevis,), the Rutelinae subfamily (e.g. Chrysina argenteola and Chrysina resplendens) and the Melolonthinae subfamily (Cyphochilus insulanus). Furthermore, structural modeling is presented on Cetonia aurata and a few more beetles to demonstrate that structural parameters can be extracted by advanced modeling of Mueller-matrix data.

    Experimental A dual rotating compensator ellipsometer (RC2, J. A. Woollam Co., Inc.) is used to record all 16 Mueller-matrix elements mij (i,j=1..4) in the spectral range 300 – 900 nm at angles of incidence in the range 20-70º. The elements are normalized to m11 and thus have values between -1 and +1. All measurements are performed on the scutellum (a small triangular part on the dorsal side of the beetles) with focusing optics resulting in a spot size of the order of 50-100 mm. The software CompleteEASE (J. A. Woollam Co., Inc.) is used for analysis.

    Results and discussion As an example, Fig. 1 shows contour plots of Mueller-matrix data measured on Cetonia aurata. This beetle has a metallic shine and if illuminated with unpolarized white light it reflects left-handed polarized green light as revealed by the non-zero Mueller-matrix elements m14 and m41 in the green spectral region for angles of incidence below about 45º. This is clearly seen in the graph to the right in Fig. 1 which shows a spectrum for Mueller-matrix element m41at 20º as well as fitted model data. A model based on a twisted lamella structure, also called Bouligand structure, is used to model the chiral nanostructure [4]. Given the complexity of the nanostructure, an excellent model fit is achieved. The obtained model parameters are the spectral variation of the refractive index of the birefringent lamellas and the pitch. The model also includes a dielectric surface layer.

     

     

     

    Fig.1. Left: Mueller-matrix data on Cetonia aurata. Each contour plot shows mij, where i and j correspond to the row and column, respectively. m11 =1 and is not shown but is replaced with a photo of the beetle. Right: Experimental and model-generated Mueller-matrix element m41at an angle of incidence of 20º.

     

    From the Mueller-matrix data one can also determine so called derived parameters including azimuth and ellipticity of the polarization ellipse and the degree of polarization. The variations of these parameters with angle of incidence are presented for a selection of scarab beetles. Examples of both left-handed and right-handed polarization effects are shown and the importance of degree of polarization will be discussed.

    Concluding remarks Mueller-matrix spectra at oblique incidence are very rich in information about reflection properties and allows parameterization of polarization parameters of the reflected light. Both left-handed and right-handed reflected light is found in scarab beetles. Mueller-matrix data can also be used for a detailed modeling of the nanostructure of the cuticle of beetles.

    AcknowledgementsFinancial support was obtained from the Knut and Alice Wallenberg foundation and the Swedish Research Council. The Museum of Natural History in Stockholm, the National Museum of Natural Science in Madrid, the Berlin Museum of Natural History and the Natural History Museum in London are acknowledged for loan of beetles.

     

    REFERENCES

    1. Michelson, A. A. “On Metallic Colouring in Birds and Insects,” Phil. Mag., 21, 554-567, 1911.
    2. Goldstein, D. H. “Polarization properties of Scarabaeidae,” Appl. Opt., 45, 7944-7950, 2006.
    3. Hodgkinson, I., Lowrey, S., Bourke, L., Parker, A. and McCall, M. W. “Mueller-matrix characterization of beetle cuticle polarized and unpolarized reflections from representative architectures,” Appl. Opt., 49, 4558-4567, 2010.
    4. Vukusic, P. and Sambles, J. R. “Photonic structures in biology,” Nature, 424, 852-855, 2003.
    5. Lenau, T. and Barfoed, M. “Colours and Metallic Sheen in Beetle Shells - A Biomimetic Search for Material Structuring Principles Causing Light Interference,” Adv. Eng. Mat., 10, 299-314. 2008.
    6. Parker, A. R. and Townley, H. E “Biomimetics of photonic nanostructures,” Nature Nanotech., 2, 347-351, 2007.
  • 6.
    Bairagi, Samiran
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Chang, Jui-Che
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tarntair, Fu-Gow
    National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan.
    Wu, Wan-Yu
    National United University, Miaoli, 36063, Taiwan.
    Gueorguiev, Gueorgui Kostov
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    de Almeida, Edward Ferraz
    Federal University of the West of Bahia, Brazil.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lin, Kun-Lin
    Taiwan Semiconductor Research Institute (TSRI), Taiwan.
    Hsu, Shao-Hui
    Taiwan Semiconductor Research Institute (TSRI), Taiwan.
    Shieh, Jia-Min
    Taiwan Semiconductor Research Institute (TSRI), Taiwan.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Horng, Ray-Hua
    National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Formation of quaternary Zn(AlxGa1−x)2O4 epilayers driven by thermally induced interdiffusion between spinel ZnGa2O4 epilayer and Al2O3 substrate2023In: Materials Today Advances, ISSN 2590-0498, Vol. 20, article id 100422Article in journal (Refereed)
    Abstract [en]

    Zinc aluminogallate, Zn(AlxGa1−x)2O4 (ZAGO), a single-phase spinel structure, offers considerable potential for high-performance electronic devices due to its expansive compositional miscibility range between aluminum (Al) and gallium (Ga). Direct growth of high-quality ZAGO epilayers however remains problematic due to the high volatility of zinc (Zn). This work highlights a novel synthesis process for high-quality epitaxial quaternary ZAGO thin films on sapphire substrates, achieved through thermal annealing of a ZnGa2O4 (ZGO) epilayer on sapphire in an ambient air setting. In-situ annealing x-ray diffraction measurements show that the incorporation of Al in the ZGO epilayer commenced at 850 °C. The Al content (x) in ZAGO epilayer gradually increased up to around 0.45 as the annealing temperature was raised to 1100 °C, which was confirmed by transmission electron microscopy (TEM) and energy dispersive x-ray spectroscopy. X-ray rocking curve measurement revealed a small full width at half maximum value of 0.72 °, indicating the crystal quality preservation of the ZAGO epilayer with a high Al content. However, an epitaxial intermediate �–(AlxGa1−x)2O3 layer (� - AGO) was formed between the ZAGO and sapphire substrate. This is believed to be a consequence of the interdiffusion of Al and Ga between the ZGO thin film and sapphire substrate. Using density functional theory, the substitution cost of Ga in sapphire was determined to be about 0.5 eV lower than substitution cost of Al in ZGO. Motivated by this energetically favorable substitution, a formation mechanism of the ZAGO and AGO layers was proposed. Spectroscopic ellipsometry studies revealed an increase in total thickness of the film from 105.07 nm (ZGO) to 147.97 nm (ZAGO/AGO) after annealing to 1100 °C, which were corroborated using TEM. Furthermore, an observed increase in the direct (indirect) optical bandgap from 5.06 eV (4.7 eV) to 5.72 eV (5.45 eV) with an increasing Al content in the ZAGO layer further underpins the formation of a quaternary ZAGO alloy with a tunable composition.

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  • 7.
    Ben Sedrine, Nabiha
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology. University of Aveiro, Portugal; University of Aveiro, Portugal.
    Zukauskaite, Agne
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering. Fraunhofer Institute Appl Solid State Phys, Germany.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Schoeche, S.
    University of Nebraska, NE 68588 USA.
    Schubert, M.
    University of Nebraska, NE 68588 USA.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Infrared dielectric functions and optical phonons of wurtzite YxAl1-xN (0 less than= x less than= 0.22)2015In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 48, no 41, p. 415102-Article in journal (Refereed)
    Abstract [en]

    YAlN is a new member of the group-III nitride family with potential for applications in next generation piezoelectric and light emitting devices. We report the infrared dielectric functions and optical phonons of wurtzite (0001) YxAl1-xN epitaxial films with 0 less than= x less than= 0.22. The films are grown by magnetron sputtering epitaxy on c-plane Al2O3 and their phonon properties are investigated using infrared spectroscopic ellipsometry and Raman scattering spectroscopy. The infrared-active E-1(TO) and LO, and the Raman active E-2 phonons are found to exhibit one-mode behavior, which is discussed in the framework of the MREI model. The compositional dependencies of the E-1(TO), E-2 and LO phonon frequencies, the high-frequency limit of the dielectric constant, epsilon(infinity), the static dielectric constant, epsilon(0), and the Born effective charge Z(B) are established and discussed.

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  • 8.
    Ben Sedrine, Nebiha
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. 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.
    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.
    Darakchieva, Vanya
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Bandgap Engineering and Optical Constants of YxAl1-xN Alloys2013In: Japanese Journal of Applied Physics, ISSN 0021-4922, E-ISSN 1347-4065, Vol. 52, no 8Article in journal (Refereed)
    Abstract [en]

    We study wurtzite Yx Al1-xN (0 andlt;= x andlt;= 0:22) films with (0001) orientation deposited by magnetron sputtering epitaxy on Si(100) substrates and we determine the alloys band gap energies and optical constants. Room temperature spectroscopic ellipsometry (SE) is employed in the energy range from 1 to 6.3 eV, and data modeling based on the standard dielectric function model is used. As a result of the SE data analysis the Yx Al1-xN refractive index and extinction coefficient are determined. The band gap of Yx Al1-xN is found to decrease linearly from 6.2 eV (x=0) down to 4.5 eV (x=0:22). We further observe an increase of the refractive index with increasing Y content; from 1.93 to 2.20 (at 2 eV) for x=0 and 0.22, respectively, reflecting the increase in material density.

  • 9.
    Bernard, M
    et al.
    CNRS, LEPES, F-38042 Grenoble 9, France Fac Sci & Tech St Jerome, MATOP, CNRS, F-13397 Marseille, France Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Deneuville, A
    CNRS, LEPES, F-38042 Grenoble 9, France Fac Sci & Tech St Jerome, MATOP, CNRS, F-13397 Marseille, France Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Thomas, O
    CNRS, LEPES, F-38042 Grenoble 9, France Fac Sci & Tech St Jerome, MATOP, CNRS, F-13397 Marseille, France Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Gergaud, P
    CNRS, LEPES, F-38042 Grenoble 9, France Fac Sci & Tech St Jerome, MATOP, CNRS, F-13397 Marseille, France Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Sandstrom, P
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Raman spectra of TiN/AlN superlattices2000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 380, no 1-2, p. 252-255Article in journal (Refereed)
    Abstract [en]

    TiN (4.5 nm)/AIN (3, 6, 22 nm) superlattices deposited by DC magnetron sputtering on MgO(001) at a temperature of 850 degreesC exhibit Raman signals. They indicate N and Ti vacancies (as in thick TiN) in TiN1-x layers (x = 3 +/- 2%). x is higher for the sample with 3-nm thick AIN layers, which is ascribed to N diffusion from AIN (standing close to the TiN interfaces) to TiN. In comparison to Raman peaks of thick ALN, there are split signals of wurzite ALN phase, and a signal from another phase, which might be defective rocksalt AIN standing close to the TiN interfaces. The Raman signals clearly show interactions between ALN and TiN layers. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 10.
    Beshkova, M.
    et al.
    Bulgarian Academy of Science, Sofia, Bulgaria.
    Zakhariev, Z.
    Bulgarian Academy of Science, Sofia, Bulgaria.
    Abrashev, M. V.
    University of Sofia, Bulgaria.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Postovit, A.
    Institute of Problem Microelectronics Technology and High Purity Materials, Moskow, Russia.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Properties of AlN epitaxial layers on 6H-SiC substrate grown by sublimation in argon, nitrogen, and their mixtures2006In: Materials Science & Engineering: B. Solid-state Materials for Advanced Technology, ISSN 0921-5107, E-ISSN 1873-4944, Vol. 129, no 1-3, p. 228-231Article in journal (Refereed)
    Abstract [en]

    Epitaxial layers of aluminum nitride (AlN) have been grown at temperature 1900 °C on 10 mm × 10 mm 6H-SiC substrate via sublimation-recondensation in RF heated graphite furnace. The source material was polycrystalline sintered AlN. Growth of AlN layers in pure nitrogen, mixed nitrogen/argon and pure argon atmosphere of 50 mbar were compared. A maximum growth rate of about 30 µm/h was achieved in pure nitrogen atmosphere. The surface morphology reflects the hexagonal symmetry of the seed, which is characteristic of an epitaxial growth for samples grown in a pure nitrogen and mixed nitrogen/argon atmosphere. X-ray diffraction (XRD) measurements show very strong and well defined (0 0 0 2) reflection positioned at around 36° in symmetric ?-2? scans. Micro-Raman spectroscopy reveals that the films have a wurtzite structure. Secondary-ion mass spectroscopy (SIMS) results showed a low concentration of carbon incorporation in the AlN layers. This study demonstrates that nitrogen is necessary for the successful epitaxial growth of AlN on 6H-SiC by sublimation. © 2006 Elsevier B.V. All rights reserved.

  • 11.
    Beshkova, Milena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Sublimation epitaxy of 3C-SiC grown at Si- and C-rich conditions2012In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 10, p. 1595-1599Article in journal (Refereed)
    Abstract [en]

    3C-SiC layers have been grown by using sublimation epitaxy at a source temperature of 2000 degrees C, under vacuum conditions (andlt;10(-5) mbar) on well oriented (on-axis) 6H-SiC (0001) substrates. Close space sublimation growth geometry has been used in a RF-heated furnace employing high-purity graphite crucible with a possibility to change the growth environment from Si vapor-rich to C vapor-rich. The optical microscopy in transmission mode reveals continuous 3C-domains for 3C-SiC with less than 0.4% 6H-inclusions for the layer grown at Si-rich conditions, and separate 3C-SiC domains for the layer grown at C-rich conditions. The type of 6H-inclusions for layers with continuous domain structure investigated by Atomic Force Microscopy (AFM) is discussed. 2Theta-omega scan shows 0006 and 111 peaks coming from the substrate and the layer, respectively with a higher intensity of the 111 peak for 3C-SiC grown at Si-rich conditions which is related with the continuous character of the 3C-SiC domains.

  • 12.
    Beshkova, Milena
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lorenzzi, J.
    UMR-CNRS.
    Jegenyes, N.
    UMR-CNRS.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Syväjärvi, Mikael
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Ferro, G.
    UMR-CNRS.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Properties of 3C-SiC Grown by Sublimation Epitaxy on Different Type of Substrates2010In: Materials Science Forum, Vols. 645-648, Transtec Publications; 1999 , 2010, Vol. 645-648, p. 183-186Conference paper (Refereed)
    Abstract [en]

    3C-SiC layers have been grown by using sublimation epitaxy at a temperature of 2000 degrees C, on different types of on-axis 6H-SiC(0001) substrates. The influence of the type of substrate on the morphology of the layers investigated by Atomic Force Microscopy (AFM) is discussed. Stacking faults are studied by reciprocal space map (RSM) which shows that double positions domains exists.

  • 13.
    Beshkova, Milena
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Vasiliauskas, Remigijus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Properties of 3C-SiC Grown by Sublimation Epitaxy2009In: ECSCRM2008,2008, 2009Conference paper (Refereed)
    Abstract [en]

      

  • 14.
    Beshkova, Milena
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Syväjärvi, Mikael
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Vasiliauskas, Remigijus
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Structural Properties of 3C-SiC Grown by Sublimation Epitaxy2009In: ECSCRM2009,2009, Materials Science Forum Vols. 615-617: Trans Tech Publications , 2009, p. 181-184Conference paper (Refereed)
    Abstract [en]

    The present paper deals with morphological and structural investigation of 3C-SiC layers grown by sublimation epitaxy on on axis 6H-SiC(0001) at source temperature 2000 °C, under vacuum conditions (<10-5 mbar) and different temperature gradients in the range of 5-8 °C/mm. The layer grown at a temperature gradient 6 °C/mm has the largest average domain size of 0.4 mm2 assessed by optical microscope in transmission mode. The rocking curve full width at half maximum (FWHM) of (111) reflection is 43 arcsec which suggests good crystalline quality. The AFM image of the same layer shows steps with height 0.25 nm and 0.75 nm which are characteristic of a stacking fault free 3C-SiC surface and c-axis repeat height, respectively.

  • 15.
    Beshkova, Milena
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Zakhariev, Z.
    Abrashev, M.V.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Low-pressure sublimation epitaxy of AlN films - growth and characterization2004In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 76, p. 143-146Article in journal (Refereed)
    Abstract [en]

    Epitaxial layers of aluminum nitride have been grown at temperatures 1900-2400degreesC on 10 x 10 mm(2) 4H-SiC substrate via sublimation recondensation in an RF heated graphite furnace. The source material was polycrystalline sintered AlN. A maximum growth rate of about 100 mum/h was achieved at 2400degreesC and seed to source distance of 1 mm. The surface morphology reflects the hexagonal symmetry of the seed suggesting an epitaxial growth. This was confirmed by X-ray diffraction (XRD). The spectra showed very strong and well-defined (0002) reflection position at around 36.04degrees in symmetric Theta-2Thetascans for all samples. Micro-Raman spectroscopy reveals that the films have a wurtzite structure. It is evidenced by the appearance of the A(1) (TO) (at 601 cm(-1)) and E-2((2)) (at 651 cm(-1)) lines in the spectra. Secondary-ion mass spectroscopy (SIMS) results showed a low concentration of carbon incorporation in the AlN films. A correlation between the growth conditions and properties of the AlN layers was established.

  • 16.
    Beshkova, Milena
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Zakhariev, Z
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Properties of AlN layers grown by sublimation epitaxy2003In: Materials Science Forum, Vols. 433-436, 2003, Vol. 433-4, p. 995-998Conference paper (Refereed)
    Abstract [en]

    Epitaxial layers of aluminum nitride (AlN)less than or equal to 80 mum thick have been grown at the temperatures 1900 and 2100 degreesC on 10x10mm(2) 4H-SiC substrates via sublimation recondensation in a RF heated graphite furnace. The source material was polyerystalline sintered AlN. A maximum growth rate of 80 mum/h was achieved at 2100degreesC and seed to source separation of I mm. The surface morphology reflects the hexagonal symmetry of the seed that suggesting an epitaxial growth. All crystals show strong and well defined single crystalline XRD patterns. Only the (002) reflection positioned at around 36.04 was observed in symmetric Theta-2Theta scan. The rocking curves FWHM (full width half maximum) and peak positions arc reported.

  • 17.
    Beshkova, Milena
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Zakhariev, Z
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Yakimova, Rositsa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Sublimation epitaxy of AIN layers on 4H-SiC depending on the type of crucible2003In: Journal of materials science. Materials in electronics, ISSN 0957-4522, E-ISSN 1573-482X, Vol. 14, no 10-12, p. 767-768Article in journal (Refereed)
    Abstract [en]

    Epitaxial layers of aluminum nitride less than or equal to335 mum thick have been grown attemperatures of 1900 and 2100degreesC on 10 x 10 mm(2) (0001)-oriented alpha(4H) silicon carbide (SiC), with growth times of 1 and 4h, via sublimation-recondensation in a RF-heated graphite furnace. The source material was polycrystalline AIN. The sublimation process was performed in three types of graphite (C) crucible: C-1, C-2 with inner diameters of 35 and 51 mm, respectively, and C-3 with the same inner diameter as C-1, but coated with a layer of TaC. The surface morphology reflects the hexagonal symmetry of the substrate, suggesting an epitaxial growth for samples grown in C-1 and C-3 crucibles for all growth conditions. The same symmetry is observed for AIN layers grown in the C-2 crucible, but only at 2100degreesC. X-ray diffraction analyses confirm the epitaxial growth of AIN samples with the expected hexagonal symmetry. A high-resolution X-ray diffractometer was used to assess the quality of the single crystals. A full width at half maximum of 242 arcsec was achieved for an AIN layer grown in the crucible coated with TaC. (C) 2003 Kluwer Academic Publishers.

  • 18.
    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)
  • 19.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Single-crystal Mo/V superlattices: growth, structure, and hydrogen uptake1994Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Fundamental studies concerning the growth, structural characterization and hydrogen uptake of single-crystal (00 l )-oriented Mo/V superlattices have been performed. The superlattices were grown by dual-target magnetron sputtering in pure Ar-atmosphere < 6·10-3 Torr on (001)-oriented MgO substrates. X-ray diffraction (XRD), X-ray and neutron reflectivity, high resolution (HR) as well as ordinary crosssectional transmission electron microscopy (XTEM) and selected area electron diffraction (SAED) were used for the structural characterization. Hydrogen depth-profiling was performed by the 15N method.

    For growth of periodic Mo/V superlattices, it is shown that substrate temperatures in the range of 600-700 °C is feasible for epitaxy. At higher growth temperatures substantial interdiffusion occurred. Furthermore, simulations of XRDpatterns gave the width of the interfaces to be ±1 monolayer (±0,154 nm) which was confirmed by XRD and HRXTEM analyses of a superlattice grown with layer thicknesses DMo=Dv=0,31 nm (2 monolayers). A transition from smooth to wavy V-layers was found to occur at a critical V-layer thickness Dc. In superlattices where the relative amount of V is large, De is large and vice versa for superlattices containing thin V-layers. In superlattices with equally thick Mo- and V-layers Dc was found to be ~2,5 nm. Mo was found to grow with a uniform thickness following the surface of the V-layers. The layer thickness fluctuations are non-accumulative and disappear if the periodicity of a growing Mo/V superlattice is changed so that Dv becomes smaller than Dc. The origin of the 3D evolution is explained in terms of surface strain and the roughening transition. The interfaces of Mo/V superlattices grown under the influence of energetic ion bombardment ranging from about 15 eV to 250 eV was studied by HRXTEM and XRD. Both techniques indicated a continous deterioration of the interface quality and an increasing amount of defects with increasing ion energy.

    The diffraction peaks from a clas of quasi-periodic superlattices which can be generated by the inflation rules A→AmB, B→A (m = positive integer) was analytically, experimentally and numerically found to be located at the wavevectors q = 2πɅ-1rγ(m)k where r and k are integers and A is an average superlattice period. The ratios, γ(m), between the thicknesses of the two superlattice building blocks, A and B, must be chosen such that γ(m) = (m + (m2 + 4) 1/2 )/2.

    The uptake of hydrogen in the superlattices is found to decrease with decreasing A and for 5,5 nm the transition between α-VHx and β-VHx is not observed. A model is proposed which explains the A-dependent behaviour of the hydrogen uptake by a transfer of interstitial electrons from Mo to V, creating a 0,49 nm wide H-free interface layer. The existence of this layer is shown both by the 15N method performed on samples containing several A:s and by combining simulations of X-ray and neutron reflectivities with measurements on superlattices loaded with either hydrogen or deuterium. The structural change of Mo/V(OOl) superlattices upon H-loading was measured by a method derived in this work which utilises a combination of X-ray reflectivity and reciprocal space mapping by XRD. The lattice parameters in the layers are measured in the growth direction as well a in the plane of the sample. It is found that the V lattice expands in the growth direction and that the hydrogenation process is associated with relaxation of coherency strain.

  • 20.
    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, Thin Film Physics. Linköping University, Faculty of Science & Engineering. 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.

  • 21.
    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.

  • 22.
    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.

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  • 23.
    Birch, Jens
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Eriksson, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Johansson, G.A.
    Biomedical and X-ray Physics, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Hertz, H.M.
    Biomedical and X-ray Physics, Royal Institute of Technology, SCFAB, SE-106 91 Stockholm, Sweden.
    Recent advances in ion-assisted growth of Cr/Sc multilayer X-ray mirrors for the water window2002Conference paper (Refereed)
    Abstract [en]

    Cr/Sc multilayer X-ray mirrors intended for normal incidence reflection in the water window wavelength range, ?=[2.4-4.4nm], have been grown by ion-assisted sputter deposition and characterized using soft and hard X-ray reflectivity. By extracting low-energy ions, with energies, Eion, ranging from 9 to 113eV and with ion-to-metal flux ratios, F, between 0.76 and 23.1, from the sputtering plasma to the growing film, the nano-structure of the multilayer interfaces could be modified. A significantly increased soft X-ray reflectivity, using ?=3.374nm, for Cr/Sc multilayers with layer thicknesses in the range 0.4-2.8nm, was obtained when high ion-to-metal flux ratios, FCr=7.1 and FSc=23.1, and low energy ions, Eion=9eV, were used. An experimental reflectivity of 5.5% was obtained at 76° for a multilayer with 400 bi-layers. Simulations of the reflectivity data showed that the interface widths are <0.425nm. It could be concluded that roughness of low spatial frequency is reduced at lower ion energies than the high spatial frequency which was eliminated at the expense of intermixing at the interfaces at higher ion energies. The predicted performance of normal incidence multilayer mirrors grown at optimum conditions and designed for ?=3.374 and 3.115nm indicates possible reflectivities of 6.5% and 14%, respectively. © 2002 Elsevier Science Ltd. All rights reserved.

  • 24.
    Birch, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Joelsson, Torbjörn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    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.
    Single crystal CrN/ScN superlattice soft X-ray mirrors: epitaxial growth, structure, and properties2006In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 514, no 1-2, p. 10-19Article in journal (Refereed)
    Abstract [en]

    Single crystal CrN/ScN superlattice films with modulation periods of 1.64 nm were grown on MgO(001) substrates. By utilizing a magnetically enhanced plasma in the vicinity of the substrate and a negative substrate bias, ion/metal nitride flux ratios of 45 and 144 were achieved during deposition of CrN and ScN, respectively. The effects of ion energies in the range [16–58 eV] and substrate temperatures in the range [535–853 °C] on the composition, interface width, crystal quality, and microstructure evolution were investigated using elastic recoil detection analysis, hard X-ray reflectivity, X-ray diffraction, and transmission electron microscopy (TEM). Minimal interface widths of 0.2 nm = 1/2 nitride unit cell were achieved at a growth temperature of 735 °C and ion energies of 24 and 28 eV for CrN and ScN, respectively. Under these conditions, also an optimum in the crystal quality was observed for near stoichiometric composition of CrN and ScN. TEM confirmed a cube-on-cube epitaxial relationship for the system with CrN(001)ScN(001)MgO(001) and CrN[100]ScN[100]MgO[100]. Also, the layers were coherently strained to each other with no misfit dislocations, threading dislocations, surface cusps, voids or gas bubbles present. Higher ion energies or lower deposition temperatures gave over-stoichiometric films with poor superlattice modulation while higher growth temperatures yielded a decreased crystal quality, due to loss of N. As-deposited superlattices with only 61 periods exhibited an absolute soft X-ray reflectance of 6.95% at an energy of 398.8 eV (Sc 2p-absorption edge) which is comparable to the performance of Cr/Sc. The compositional modulation and phase structure was stable during extended annealing at 850 °C, which is the highest thermal stability for an X-ray multilayer mirror. It is concluded that the ScN layers serve as effective diffusion barriers to hinder decomposition of the CrN layers and stabilize the pseudomorphic superlattice structure. Nanoindentation experiments showed that the hardness of the CrN/ScN superlattice films was 19 GPa.

  • 25.
    Broekhuijsen, Sjoerd
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Vorobiev, Alexei
    Department of Physics and Astronomy, Material Physics, Uppsala University, Uppsala, Sweden; Institut Max von Laue—Paul Langevin, Grenoble, France.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Synthesis and characterization of 11B4C containing Ni/Ti multilayers using combined neutron and X-ray reflectometry2023In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 13, no 4, p. 1140-1149Article in journal (Refereed)
    Abstract [en]

    The performance of multilayers in optical components, such as those used in neutron scattering instruments, is crucially dependent on the achievable interface width. We have shown how the interface width of Ni/Ti multilayers can be improved using the incorporation of B4C to inhibit the formation of nanocrystals and limit interdiffusion and intermetallic reactions at the interfaces. A modulated ion-assistance scheme was used to prevent intermixing and roughness accumulation throughout the layer stack. In this work we investigate the incorporation of low-neutron-absorbing 11B4C for Ni/Ti neutron multilayers. Combined fitting of neutron reflectivity and X-ray reflectivity measurements shows an elimination of accumulated roughness for the 11B4C containing multilayers with a mean interface width of 4.5 Å, resulting in an increase in reflectivity at the first Bragg peak by a factor of 2.3 and 1.5 for neutron and X-ray measurements, respectively.

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  • 26.
    Buyanova, Irina A
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Seppänen, Timo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pearton, SJ
    Polimeni, A
    Capizzi, M
    Brandt, MS
    Bihler, C
    Hong, YG
    Tu, CW
    Unusual effects of hydrogen on electronic and lattice properties of GaNP alloys2006In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 376, p. 568-570Article in journal (Refereed)
    Abstract [en]

    Hydrogen incorporation is shown to cause passivation of various N-related localized states and partial neutralization of N-induced changes in the electronic structure of the GaNxP1-x alloys with x < 0.008. According to the performed X-ray diffraction measurements, the hydrogenation is also found to cause strong expansion of the GaNP lattice which even changes from a tensile strain in the as-grown GaNP epilayers to a compressive strain in the post-hydrogenated structures with the highest H concentration. By comparing results obtained using two types of hydrogen treatments, i.e. by implantation from a Kaufman source and by using a remote dc H plasma, the observed changes are shown to be inherent to H due to its efficient complexing with N atoms, whereas possible effects of implantation damage are only marginal. (c) 2005 Elsevier B.V. All rights reserved.

  • 27.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Wei Min
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Felici, M.
    Polimeni, A.
    Capizzi, M.
    Hong, Y.G.
    Xin, H.P.
    Tu, C.W.
    Unusual effects of hydrogen in GaNP alloys: A general property of dilute nitrides2005In: 2005 MRS Spring Meeting,2005, 2005, p. 135-Conference paper (Other academic)
  • 28.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Felici, M.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Polimeni, A.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Capizzi, M.
    Dipartimento di Fisica, Università di Roma “La Sapienza,” Roma, Italy .
    Hong, Y. G.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Xin, H. P.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California, USA .
    Direct experimental evidence for unusual effects of hydrogen on the electronic and vibrational properties of GaNxP1−x alloys: a proof for a general property of dilute nitrides2004In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 70, no 24, p. 245215-245219Article in journal (Refereed)
    Abstract [en]

    Direct experimental evidence for dramatic effects of hydrogen incorporation on the electronic structure and lattice properties of GaNxP1−x alloys is presented. By employing photoluminescence excitation spectroscopy, postgrowth hydrogenation is shown to reopen the band gap of the GaNP alloys and to efficiently reduce the N-induced coupling between the conduction band states. By Raman spectroscopy, these effects are shown to be accompanied by hydrogen-induced breaking of the Ga-P bond in the alloy, evident from disappearance of the corresponding vibrational mode. According to the performed Raman and x-ray diffraction measurements, the hydrogenation is also found to cause a strong expansion of the GaNP lattice, which changes the sign of strain from tensile in the as-grown GaNP epilayers to compressive in the posthydrogenated structures, due to the formation of complexes between N and H.

  • 29.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Polimeni, A.
    Capizzi, M.
    Hong, Y. G.
    Tu, C. W.
    Effects of hydrogen on electronic and crystalline structure of GaNP2004In: EMRS-2004 Spring Meeting,2004, 2004Conference paper (Other academic)
  • 30.
    Chang, Jui-Che
    et al.
    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.
    Kostov Gueorguiev, Gueorgui
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sandström, Per
    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.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Domain epitaxial growth of Ta3N5 film on c-plane sapphire substrate2022In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 443, article id 128581Article in journal (Refereed)
    Abstract [en]

    Tritantalum pentanitride (Ta3N5) semiconductor is a promising material for photoelectrolysis of water with high efficiency. Ta3N5 is a metastable phase in the complex system of TaN binary compounds. Growing stabilized single-crystal Ta3N5 films is correspondingly challenging. Here, we demonstrate the growth of a nearly single-crystal Ta3N5 film with epitaxial domains on c-plane sapphire substrate, Al2O3(0001), by magnetron sputter epitaxy. Introduction of a small amount ~2% of O2 into the reactive sputtering gas mixed with N2 and Ar facilitates the formation of a Ta3N5 phase in the film dominated by metallic TaN. In addition, we indicate that a single-phase polycrystalline Ta3N5 film can be obtained with the assistance of a Ta2O5 seed layer. With controlling thickness of the seed layer smaller than 10 nm and annealing at 1000 °C, a crystalline β phase Ta2O5 was formed, which promotes the domain epitaxial growth of Ta3N5 films on Al2O3(0001). The mechanism behind the stabilization of the orthorhombic Ta3N5 structure resides in its stacking with the ultrathin seed layer of orthorhombic β-Ta2O5, which is energetically beneficial and reduces the lattice mismatch with the substrate.

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  • 31.
    Chang, Jui-Che
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sortica, Mauricio A.
    Uppsala Univ, Sweden.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hu, Zhang-Jun
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Primetzhofer, Daniel
    Uppsala Univ, Sweden.
    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.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Orthorhombic Ta3-xN5-yOy thin films grown by unbalanced magnetron sputtering: The role of oxygen on structure, composition, and optical properties2021In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 406, article id 126665Article in journal (Refereed)
    Abstract [en]

    Direct growth of orthorhombic Ta3N5-type Ta-O-N compound thin films, specifically Ta3-xN5-yOy, on Si and sapphire substrates with various atomic fractions is realized by unbalanced magnetron sputtering. Low-degree fiber-textural Ta3-xN5-yOy films were grown through reactive sputtering of Ta in a gas mixture of N-2, Ar, and O-2 with keeping a partial pressure ratio of 3:2:0.1 in a total working pressure range of 5-30 mTorr. With increasing total pressure from 5 to 30 mTorr, the atomic fraction of O in the as-grown Ta3-xN5-yOy films was found to increase from 0.02 to 0.15 while that of N and Ta decrease from 0.66 to 0.54 and 0.33 to 0.31, respectively, leading to a decrease in b lattice constant up to around 1.3%. Metallic TaNx phases were formed without oxygen. For a working pressure of 40 mTorr, an amorphous, O-rich Ta-N-O compound film with a high O fraction of similar to 0.48, was formed, mixed with non-stoichiometric TaON and Ta2O5. By analyzing the plasma discharge, the increasing O incorporation is associated with oxide formation on top of the Ta target due to a higher reactivity of Ta with O than with N. The increase of O incorporation in the films also leads to a optical bandgap widening from similar to 2.22 to similar to 2.96 eV, which is in agreement with the compositional and structural changes from a crystalline Ta3-xN5-yOy to an amorphous O-rich Ta-O-N compound.

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  • 32.
    Chang, Jui-Che
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tseng, Eric Nestor
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lo, Yi-Ling
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Nayak, Sanjay Kumar
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, Faculty of Science & Engineering.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Horng, Ray-Hua
    National Yang Ming Chiao Tung University, Hsinchu, 30010, Taiwan.
    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.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    HiPIMS-grown AlN buffer for threading dislocation reduction in DC-magnetron sputtered GaN epifilm on sapphire substrate2023In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 217, article id 112553Article in journal (Refereed)
    Abstract [en]

    Gallium nitride (GaN) epitaxial films on sapphire (Al2O3) substrates have been grown using reactive magnetron sputter epitaxy with a liquid Ga target. Threading dislocations density (TDD) of sputtered GaN films was reduced by using an inserted high-quality aluminum nitride (AlN) buffer layer grown by reactive high power impulse magnetron sputtering (R-HiPIMS) in a gas mixture of Ar and N2. After optimizing the Ar/N2 pressure ratio and deposition power, a high-quality AlN film exhibiting a narrow full-width at half-maximum (FWHM) value of the double-crystal x-ray rocking curve (DCXRC) of the AlN(0002) peak of 0.086° was obtained by R-HiPIMS. The mechanism giving rise the observed quality improvement is attributed to the enhancement of kinetic energy of the adatoms in the deposition process when operated in a transition mode. With the inserted HiPIMS-AlN as a buffer layer for direct current magnetron sputtering (DCMS) GaN growth, the FWHM values of GaN(0002) and (10 1‾ 1) XRC decrease from 0.321° to 0.087° and from 0.596° to 0.562°, compared to the direct growth of GaN on sapphire, respectively. An order of magnitude reduction from 2.7 × 109 cm−2 to 2.0 × 108 cm−2 of screw-type TDD calculated from the FWHM of the XRC data using the inserted HiPIMS-AlN buffer layer demonstrates the improvement of crystal quality of GaN. The result of TDD reduction using the HiPIMS-AlN buffer was also verified by weak beam dark-field (WBDF) cross-sectional transmission electron microscopy (TEM).

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  • 33.
    Chen, Ruei-San
    et al.
    National Taiwan University of Science and Technology, Taiwan.
    Tang, Chih-Che
    Department of Electronic Engineering, National Taiwan University of Science and Technology, Taiwan.
    Hsiao, Ching-Lien
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Holtz, Per Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Electronic transport properties in aluminum indium nitride nanorods grown by magnetron sputter epitaxy2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 285, p. 625-628Article in journal (Refereed)
    Abstract [en]

    The electronic transport properties of the wide-bandgap aluminum indium nitride (AlInN) nanorods (NRs) grown by ultrahigh-vacuum magnetron sputter epitaxy (MSE) have been studied. The conductivities of the ternary compound nanostructure locates at the value of 15 Q-1 cm -1, which is respectively one and two orders of magnitude lower than the binary GaN and InN counterparts grown by chemical vapor deposition (CVD). The very shallow donor level/band with the activation energy at 11 + 2 meV was obtained by the temperature-dependent measurement. In addition, the photoconductivity has also been investigated. The photoconductive (PC) gain of the NRs device can reach near 2400 under a low bias at 0.1 V and the light intensity at 100W m-2 for ultraviolet response in vacuum. The power-insensitive gain and ambience-dependent photocurrent are also observed, which is attributed to the probable surfacecontrolled PC mechanism in this ternary nitride nanostructure.

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  • 34.
    Chen, Yen-Ting
    et al.
    Academic Sinica, Taiwan .
    Araki, Tsutomu
    Ritsumeikan University, Japan .
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chen, Li-Chyong
    National Taiwan University, Taiwan .
    Chen, Kuei-Hsien
    Academic Sinica, Taiwan .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Nanishi, Yasushi
    Ritsumeikan University, Japan .
    Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 20, p. 203108-Article in journal (Refereed)
    Abstract [en]

    Nucleation mechanism of catalyst-free GaN nanorod grown on Si(111) is investigated by the fabrication of uniform and narrow (andlt; 35 nm) nanorods without a pre-defined mask by molecular beam epitaxy. Direct evidences show that the nucleation of GaN nanorods stems from the sidewall of the underlying islands down to the Si(111) substrate, different from commonly reported ones on top of the island directly. Accordingly, the growth and density control of the nanorods is exploited by a "narrow-pass" approach that only narrow nanorod can be grown. The optimal size of surrounding non-nucleation area around single nanorod is estimated as 88 nm.

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  • 35.
    Chen, Yen-Ting
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Karlsson, K. Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, no 21482, p. 1-7Article in journal (Refereed)
    Abstract [en]

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated.

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  • 36.
    Chubarova, E.
    et al.
    Royal Institute Technology KTH.
    Nilsson, D.
    Royal Institute Technology KTH.
    Lindblom, M.
    Royal Institute Technology KTH.
    Reinspach, J.
    Royal Institute Technology KTH.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Vogt, U.
    Royal Institute Technology KTH.
    Hertz, H. M.
    Royal Institute Technology KTH.
    Holmberg, A.
    Royal Institute Technology KTH, Department Appl Phys, SE-10691 Stockholm, Sweden.
    Platinum zone plates for hard X-ray applications2011In: Microelectronic Engineering, ISSN 0167-9317, E-ISSN 1873-5568, Vol. 88, no 10, p. 3123-3126Article in journal (Refereed)
    Abstract [en]

    We describe the fabrication and evaluation of platinum zone plates for 5-12 kV X-ray imaging and focusing. These nano-scale circular periodic structures are fabricated by filling an e-beam generated mold with Pt in an electroplating process. The plating recipe is described. The resulting zone plates, having outer zone widths of 100 and 50 nm, show good uniformity and high aspect ratio. Their diffraction efficiencies are 50-70% of the theoretical, as measured at the European Synchrotron Radiation Facility. Platinum shows promise to become an attractive alternative to present hard X-ray zone plate materials due to its nano-structuring properties and the potential for zone-plate operation at higher temperatures.

  • 37.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Tungasmita, Sukkaneste
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Strain evolution in high temperature AlN buffer layers for HVPE-GaN growth2002In: Physica status solidi. A, Applied research, ISSN 0031-8965, E-ISSN 1521-396X, Vol. 190, no 1, p. 59-64Article in journal (Refereed)
    Abstract [en]

    High temperature AlN buffer layers are deposited on a-plane sapphire by reactive magnetron sputtering. The effect of the buffer thickness on the AlN structural properties and surface morphology are studied in correlation with the subsequent hydride vapour phase epitaxy of GaN. A minimum degree of mosaicity and screw dislocation density is determined for a 50 nm thick AlN buffer. With increasing the AlN thickness, a strain relaxation occurs as a result of misfit dislocation generation and higher degree of mosaicity. A blue shift of the E-1(TO) frequency evaluated by means of infrared reflection spectroscopy is linearly correlated with an increase in biaxial compressive stress in the films through the IR stress factor k(E1)(b) = 2.57 +/- 0.26 cm(-1) GPa(-1).

  • 38.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology.
    Schubert, M
    Paskova, Tanja
    Linköping University, Department of Physics, Chemistry and Biology.
    Tungasmita, S
    Wagner, G
    Kasic, A
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Strain-related structural and vibrational properties of thin epitaxial AIN layers2004In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 70, no 4, p. 045411-Article in journal (Refereed)
    Abstract [en]

    The effect of film thickness on the strain and structural properties of thin epitaxial AIN films has been investigated by high resolution x-ray diffraction techniques and transmission electron microscopy. As a result a sublayer model of the degree of strain and related defects for all films is proposed. A sublayer with low defect density and a strain gradient is found to be present in all films and it reaches a maximum thickness of 65 nm. The films are compressively strained and the strain relaxation after a thickness of 65 nm is shown to be accompanied by misfit dislocation generation and increase of the mosaic tilt. The vibrational properties of the films have been studied by generalized infrared spectroscopic ellipsometry. The proposed sublayer model has been successfully applied to the analysis of the ellipsometry data through model calculations of the infrared dielectric function which confirm the sublayer model. It is found that the strain gradient results in a gradient of the phonon mode frequencies and broadening parameter. The initial strain relaxation in the films leads to narrowing of the observable infrared modes, while further strain relaxation broadens the modes when substantial defect generation occurs.

  • 39.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Tungasmita, Sukkaneste
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Deformation potentials of the E-1(TO) mode in AlN2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 80, no 13, p. 2302-2304Article in journal (Refereed)
    Abstract [en]

    The deformation potentials of the E-1(TO) mode in AlN are experimentally determined by combining infrared reflection spectroscopy and x-ray diffraction measurements and using a reported value of the Raman-stress factor for hydrostatically stressed bulk AlN. The deformation potentials are found to strongly depend on published stiffness constants of AlN. A comparison with earlier theoretically calculated values of the deformation potentials is made. (C) 2002 American Institute of Physics.

  • 40.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Schubert, M.
    Fak. für Phys./Geowiss., Iniversität Leipzig, 04103 Leipzig, Germany.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Kasic, A.
    Tungasmita, Sukkaneste
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Generalized infrared ellipsometry study of thin epitaxial AlN layers with complex strain behavior2003Conference paper (Refereed)
    Abstract [en]

    The effect of film thickness on the strain and structural properties of thin epitaxial AlN films has been investigated, and a sub-layer model of the degree of strain and related defects for all films is suggested. The vibrational properties of the films have been studied by generalized infrared spectroscopic ellipsometry. The proposed sub-layer model has been successfully applied to the analysis of the ellipsometry data trough model calculations of the infrared dielectric function. © 2003 Elsevier B.V. All rights reserved.

  • 41.
    Dorri, Samira
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Stendahl, Sjoerd
    Department of Physics and Astronomy, Material Physics, Uppsala University, Uppsala, Sweden.
    Devishvili, Anton
    Institut Laue-Langevin, Grenoble, France.
    Vorobiev, Alexei
    Department of Physics and Astronomy, Material Physics, Uppsala University, Uppsala, Sweden; Institut Laue-Langevin, Grenoble, France .
    Eriksson, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O.Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Enhanced quality of single crystal CrBx/TiBy diboride superlattices by controlling boron stoichiometry during sputter deposition2024In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, article id 159606Article in journal (Refereed)
    Abstract [en]

    Single-crystal CrB2/TiB2 diboride superlattices with well-defined layers are promising candidates for neutron optics. However, excess B in sputter-deposited TiBy using a single TiB2 target deteriorates the structural quality of CrBx/TiBy (0001) superlattices. We study the influence of co-sputtering of TiB2 + Ti on the stoichiometry and crystalline quality of 300-nm-thick TiBy single layers and CrBx/TiBy (0001) superlattices on Al2O3(0001) substrates grown by DC magnetron sputter epitaxy at growth-temperatures TS ranging from 600 to 900 °C. By controlling the relative applied powers to the TiB2 and Ti magnetrons, y could be reduced from 3.3 to 0.9. TiB2.3 grown at 750 °C exhibited epitaxial domains about 10x larger than non-co-sputtered films. Close-to-stoichiometry CrB1.7/TiB2.3 superlattices with modulation periods Λ = 6 nm grown at 750 °C showed the highest single crystal quality and best layer definition. TiB2.3 layers display rough top interfaces indicating kinetically limited growth while CrB1.7 forms flat and abrupt top interfaces indicating epitaxial growth with high adatom mobility.

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  • 42.
    Dorri, Samira
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois at Urbana-Champaign, USA; National Taiwan University of Science and Technology, Taiwan.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bakhit, Babak
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Oxidation kinetics of overstoichiometric TiB2 thin films grown by DC magnetron sputtering2022In: Corrosion Science, ISSN 0010-938X, E-ISSN 1879-0496, Vol. 206, article id 110493Article in journal (Refereed)
    Abstract [en]

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

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  • 43.
    Eklund, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Emmerlich, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Wilhelmsson, Ola
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
    Isberg, Peter
    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.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jansson, Ulf
    Department of Materials Chemistry, The Ångström Laboratory, Uppsala University, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Structural, electrical, and mechanical properties of nc-TiC/a-SiC nanocomposite thin films2005In: Journal of Vacuum Science & Technology B, ISSN 1071-1023, E-ISSN 1520-8567, Vol. 23, no 6, p. 2486-2495Article in journal (Refereed)
    Abstract [en]

    We have synthesized Ti–Si–C nanocomposite thin films by dc magnetron sputtering from a Ti3SiC2 compound target in an Ar discharge on Si(100), Al2O3(0001), and Al substrates at temperatures from room temperature to 300  °C. Electron microscopy, x-ray diffraction, and x-ray photoelectron spectroscopy showed that the films consisted of nanocrystalline (nc-) TiC and amorphous (a-) SiC, with the possible presence of a small amount of noncarbidic C. The growth mode was columnar, yielding a nodular film-surface morphology. Mechanically, the films exhibited a remarkable ductile behavior. Their nanoindentation hardness and E-modulus values were 20 and 290  GPa, respectively. The electrical resistivity was 330  µ  cm for optimal Ar pressure (4  mTorr) and substrate temperature (300  °C). The resulting nc-TiC/a-SiC films performed well as electrical contact material. These films' electrical-contact resistance against Ag was remarkably low, 6  µ at a contact force of 800  N compared to 3.2  µ for Ag against Ag. The chemical stability of the nc-TiC/a-SiC films was excellent, as shown by a Battelle flowing mixed corrosive-gas test, with no N, Cl, or S contaminants entering the bulk of the films.

  • 44.
    Ektarawong, Annop
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Max Planck Institute Eisenforsch GmbH, Germany.
    Configurational order-disorder induced metal-nonmetal transition in B13C2 studied with first-principles superatom-special quasirandom structure method2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 1, article id 014202Article in journal (Refereed)
    Abstract [en]

    Due to a large discrepancy between theory and experiment, the electronic character of crystalline boron carbide B13C2 has been a controversial topic in the field of icosahedral boron-rich solids. We demonstrate that this discrepancy is removed when configurational disorder is accurately considered in the theoretical calculations. We find that while the ordered ground state B13C2 is metallic, the configurationally disordered B13C2, modeled with a superatom-special quasirandom structure method, goes through a metal to nonmetal transition as the degree of disorder is increased with increasing temperature. Specifically, one of the chain-end carbon atoms in the CBC chains substitutes a neighboring equatorial boron atom in a B-12 icosahedron bonded to it, giving rise to a B11Ce(BBC) unit. The atomic configuration of the substitutionally disordered B13C2 thus tends to be dominated by a mixture between B-12(CBC) and B11Ce(BBC). Due to splitting of valence states in B11Ce(BBC), the electron deficiency in B-12(CBC) is gradually compensated.

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  • 45.
    Ektarawong, Annop
    et al.
    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.
    Hultman, Lars
    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, Thin Film Physics. Linköping University, The Institute of Technology.
    First-principles study of configurational disorder in B4C using a superatom-special quasirandom structure method2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 2, article id 024204Article in journal (Refereed)
    Abstract [en]

    Configurationally disordered crystalline boron carbide, with the composition B4C, is studied using first-principles calculations. We investigate both dilute and high concentrations of carbon-boron substitutional defects. For the latter purpose, we suggest a superatoms picture of the complex structure and combine it with a special quasirandom structure approach for disorder. In this way, we model a random distribution of high concentrations of the identified low-energy defects: (1) bipolar defects and (2) rotation of icosahedral carbon among the three polar-up sites. Additionally, the substitutional disorder of the icosahedral carbon at all six polar sites, as previously discussed in the literature, is also considered. Two configurational phase transitions from the ordered to the disordered configurations are predicted to take place upon an increase in temperature using a mean-field approximation for the entropy. The first transition, at 870 K, induces substitutional disorder of the icosahedral carbon atoms among the three polar-up sites; meanwhile the second transition, at 2325 K, reveals the random substitution of the icosahedral carbon atoms at all six polar sites coexisting with bipolar defects. Already the first transition removes the monoclinic distortion existing in the ordered ground-state configuration and restore the rhombohedral system (R3m). The restoration of inversion symmetry yielding the full rhombohedral symmetry (R (3) over barm) on average, corresponding to what is reported in the literature, is achieved after the second transition. Investigating the effects of high pressure on the configurational stability of the disordered B4C phases reveals a tendency to stabilize the ordered ground-state configuration as the configurationally ordering/disordering transition temperature increases with pressure exerted on B4C. The electronic density of states, obtained from the disordered phases, indicates a sensitivity of the band gap to the degree of configurational disorder in B4C.

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  • 46.
    Ektarawong, Annop
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Simak, Sergey
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tasnádi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Wang, Fei
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Max Planck Institute Eisenforsch GmbH, Germany.
    Effects of configurational disorder on the elastic properties of icosahedral boron-rich alloys based on B6O, B13C2, and B4C, and their mixing thermodynamics2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 13, article id 134503Article in journal (Refereed)
    Abstract [en]

    The elastic properties of alloys between boron suboxide (B6O) and boron carbide (B13C2), denoted by (B6O)1−x(B13C2)x, as well as boron carbide with variable carbon content, ranging from B13C2 to B4C are calculated from first-principles. Furthermore, the mixing thermodynamics of (B6O)1−x(B13C2)x is studied. A superatom-special quasirandom structure approach is used for modeling different atomic configurations, in which effects of configurational disorder between the carbide and suboxide structural units, as well as between boron and carbon atoms within the units, are taken into account. Elastic properties calculations demonstrate that configurational  disorder in B13C2, where a part of the C atoms in the CBC chains substitute for B atoms in the B12 icosahedra, drastically increase the Young’s and shear modulus, as compared to an atomically ordered state, B12(CBC). These calculated elastic moduli of the disordered state are in excellent agreement with experiments. Configurational disorder between boron and carbon can also explain the experimentally observed almost constant elastic moduli of boron carbide as the carbon content is changed from B4C to B13C2. The elastic moduli of the (B6O)1−x(B13C2)x system are also practically unchanged with composition if boron-carbon disorder is taken into account. By investigating the mixing thermodynamics of the alloys, in which the Gibbs free energy is determined within the mean-field approximation for the configurational entropy, we outline the pseudo-binary phase diagram of (B6O)1−x(B13C2)x. The phase diagram reveals the existence of a miscibility gap at all temperatures up to the melting point. Also, the coexistence of B6O-rich as well as ordered or disordered B13C2-rich domains in the material prepared through equilibrium routes is predicted.

  • 47. Engstrom, C.
    et al.
    Berlind, Torun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Ivanov, I.P.
    Cypress Semiconductor Corporation, 2401 East 86th Street, Bloomington, MN 55425, United States.
    Kirkpatrick, S.R.
    Department of Mechanical Engineering, Center for Mat. Res. and Analysis, University of Nebraska-Lincoln, 255 WSEC, Lincoln, NE 68588-0656, United States.
    Rohde, S.
    Department of Mechanical Engineering, Center for Mat. Res. and Analysis, University of Nebraska-Lincoln, 255 WSEC, Lincoln, NE 68588-0656, United States.
    Design, plasma studies, and ion assisted thin film growth in an unbalanced dual target magnetron sputtering system with a solenoid coil2000In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 56, no 2, p. 107-113Article in journal (Refereed)
    Abstract [en]

    An original design and solution to the problem of magnetic field interactions in a vacuum chamber between two unbalanced magnetron sputtering sources and a solenoid coil serving to increase plasma density in near substrate position, is presented. By changing the solenoid coil current strength and direction, plasma growth conditions in an argon discharge and Ti-magnetron cathodes were found to vary in a broad region. Langmuir probe analysis shows that an increase in the coil current from 0 to 6 A caused plasma and substrate floating potentials to change from -7 to -30 V and from +1 to -10 V, respectively, as well as increasing the ion densities to a biased substrate from 0.2 to 5.2 mA cm-2 for each of the magnetrons. By using a ferro-powder magnetic field model, as well as finite element method analysis, we demonstrate the interference of the three magnetic fields - those of the two magnetrons and the solenoid coil. X-ray diffraction and transmission electron microscopy were used to study the microstructure and morphology of Ti-films grown under different ion bombardment conditions. At low Ar-ion-to-Ti-atom arrival rate ratios, Jion/Jn to approximately 1.5, at the substrate, variations of the ion energy, Eion, from 8 to 70 eV has only a minor effect on the microstructure and film preferred crystallographic orientation, resulting in an open/porous structure with defect-rich grains. At a higher Jion/Jn value of approximately 20, films with a well-defined dense structure were deposited at ion energies of 80 eV. The increase in ion flux also resulted in changes of the Ti film preferred orientation, from an (0 0 0 2) preferred orientation to a mixture of (0 0 0 2) and (1 0 1¯ 1) orientations.

  • 48. Engstrom, C
    et al.
    Madan, A
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Nastasi, M
    Northwestern Univ, Advanced Coating Technol Grp, Evanston, IL 60201 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Barnett, SA
    Northwestern Univ, Advanced Coating Technol Grp, Evanston, IL 60201 USA Northwestern Univ, Dept Mat Sci & Engn, Evanston, IL USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Univ Calif Los Alamos Natl Lab, Los Alamos, NM USA.
    High-temperature stability of epitaxial, non-isostructural Mo/NbN superlattices2000In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 15, no 2, p. 554-559Article in journal (Refereed)
    Abstract [en]

    The effect of 1000 degrees C vacuum annealing on the structure and hardness of epitaxial Mo/NbN superlattice thin films was studied. The intensity of superlattice satellite peaks, measured by x-ray diffraction, decreased during annealing while new peaks corresponding to a MoNbN ternary phase appeared. The results are consistent with the Mo-Nb-N phase diagram, which shows no mutual solubility between Mo, NbN, and MoNbN. Even after 3-h anneals and a loss of most of the superlattice peak intensity, the room-temperature hardness was the same as for as-deposited superlattices, The retained hardness suggests that a residual nanocomposite structure is retained even after the formation of the ternary structure.

  • 49.
    Eriksson, Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Broekhuijsen, Sjoerd
    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.
    Schell, Norbert
    Helmholtz-Zentrum Geesthacht, Centre for Materials and Coastal Research, Institute for Materials Research, Germany.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Morphology control in Ni/Ti multilayer neutron mirrors by ion-assisted interface engineering and B4C incorporation2023In: Optical Materials Express, ISSN 2159-3930, E-ISSN 2159-3930, Vol. 13, no 5, p. 1424-1439Article in journal (Refereed)
    Abstract [en]

    The optical contrast and minimum layer thickness of Ni/Ti broadband neutron multilayer supermirrors is usually hampered by an interface width, typically 0.7 nm, caused by nanocrystallites, interdiffusion, and/or intermixing. We explore the elimination of nanocrystallites in combination with interface smoothening by modulation of ion assistance during magnetron sputter deposition of 0.8 to 6.4 nm thick Ni and Ti layers. The amorphization is achieved through incorporation of natural B4C where B and C preferably bond to Ti. A two-stage substrate bias was applied to each layer; -30 V for the initial 1 nm followed by -100 V for the remaining part, generating multilayer mirrors with interface widths of 0.40-0.45 nm. The results predict that high performance supermirrors with m-values as high as 10 are feasible by using 11B isotope-enriched B4C combined with temporal control of the ion assistance.

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  • 50.
    Eriksson, Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    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.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Reflectivity and structural evolution of Cr/Sc and nitrogen containing Cr/Sc multilayers during thermal annealing2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 6, p. 063516-Article in journal (Refereed)
    Abstract [en]

    It is shown that the thermal stability in vacuum of Cr/Sc multilayer thin films used as reflective optical components in soft x-ray instrumentation has substantial dependence on incorporation of N. The thermal stability is increased by incorporating 34 at.% of N in Cr/Sc multilayers. A pure Cr/Sc multilayer x-ray mirror starts a continuous degradation already at ~100 °C with a complete destruction of the multilayer at 500 °C. The resulting structure is a mixture of Cr and Sc nanocrystallites. The degradation can be described by linear diffusion theory and is suggested to be due to the formation of uniformly distributed phase-separated nanocrystallites followed by an Ostwald ripening process with an apparent activation energy of 0.5 eV. At the multilayer-substrate interface, a 7 nm thin Sc-Si layer is formed which effectively hinders indiffusion of Si and outdiffusion of Cr and Sc. A nitrided multilayer, initially consisting of crystalline fcc CrNx and fcc ScNy layers (x and y<1), is observed to improve in structural quality up to ~250 °C where it is stable for more than 12 h. At ~330 °C, the multilayer separates into regions with two multilayer periods, differing by less than 0.04 nm, which are stable at 420 °C over an extended period of time >40 h. It is proposed that the separation into the different multilayer periods is a consequence of redistribution of N within the Cr layers. Sc is observed to be stabilized in the ScN layers, which, in turn, inhibit the formation of a Sc-Si barrier layer at the substrate leading to a strong exchange of Si and Cr across the film substrate. This leads to a Cr-Si/ScN layered structure close to the substrate and chromium silicide crystallites inside the substrate. Close to the top of the multilayer, a CrN/ScN multilayer appears to be retained.

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