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  • 1. Abadei, S.
    et al.
    Gevorgian, S.
    Cho, C. R.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Low-frequency and microwave performances of laser-ablated epitaxial Na0.5K0.5NbO3 films on high-resistivity SiO2/Si substrates2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, nr 4, s. 2267-2276Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dielectric properties of laser-ablated 0.5-mum-thick c-axis epitaxial Na0.5K0.5NbO3 (NKN) films on high-resistivity (>7.7 kOmega cm) silicon SiO2/Si substrates are studied experimentally in the temperature interval of 30-320 K and at frequencies of 1.0 MHz-40 GHz. The films are grown by laser ablation from a stoichiometric target. For the measurements, planar 0.5-mum-thick gold electrodes (interdigital and straight slot) are photolithography defined on the top surface of NKN films. The slot width between the electrodes is 2.0 or 4.0 mum. At low frequencies (f<1.0 GHz), the structure performance is that of a typical metal-dielectric-semiconductor type, where two of this type of capacitor are connected back to back. At these frequencies, the large change in the capacitance (more than 10 times at 1.0 MHz), due to the applied dc field, is mainly due to the changes in depletion layer thickness at the surface of silicon. The associated losses are also large, tan delta>1. At microwave frequencies (f>10 GHz), the voltage dependence of the capacitance is given by the NKN film. More than a 13% capacitance change at 40 V dc bias and a Q factor of more than 15 are observed at 40 GHz, which make the structure useful for applications in electrically tunable millimeter-wave devices.

  • 2. Aberg, D
    et al.
    Linnarsson, M K
    KTH, Skolan för informations- och kommunikationsteknik (ICT).
    Svensson, B G
    Hallberg, T
    Lindstrom, J L
    Ultrashallow thermal donor formation in silicon by annealing in ambient oxygen1999Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 85, s. 8054-8059Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Czochralski-grown silicon wafers doped with phosphorus (similar to 10(14) cm(-3)) have been annealed in nitrogen, wet nitrogen, oxygen, argon, and vacuum ambients at 470 degrees C for times up to 500 h. Sample characterization was made using predominantly electrical techniques such as admittance spectroscopy and thermally stimulated capacitance measurements but also secondary ion mass spectrometry (SIMS) and Fourier transform infrared spectroscopy were employed. In all samples, an increasing concentration of free carrier electrons is observed with increasing annealing time, reaching a maximum of similar to 10(16) cm(-3) at 100 h. For durations in excess of 100 h gradual decrease of the free electron concentration takes place except for the samples treated in wet nitrogen and oxygen atmospheres, which display donors stable even after 200 h. These stable centers are found to have shallower donor level positions in the energy band gap (similar to 25 meV below the conduction band edge E-c) than those of the centers formed in vacuum, argon, and nitrogen atmospheres (similar to 35 meV below E-c). The latter centers are associated with the well-established shallow thermal donors (STDs) while the origin of the former ones, which are labeled ultrashallow thermal donors (USTDs) is less known. However, on the basis of a wealth of experimental results we show that the USTDs are most likely perturbated STDs modified through interaction with fast-in diffusing oxygen species, possibly oxygen dimers. Further, comparison between the electrical data and the SIMS measurements reveals unambiguously that neither the STD nor the USTD centers involve nitrogen, in contrast to recent suggestions in the literature. (C) 1999 American Institute of Physics. [S0021-8979(99)06512-3].

  • 3. Aberg, J
    et al.
    Persson, S
    Hellberg, Per-Erik
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Zhang, Shi-Li
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Smith, U
    Ericson, F
    Engstrom, M
    Kaplan, W
    Electrical properties of the TiSi2-Si transition region in contacts: The influence of an interposed layer of Nb2001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, nr 5, s. 2380-2388Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of an interposed ultrathin Nb layer between Ti and Si on the silicide formation and the electrical contact between the silicide formed and the Si substrate is investigated. The presence of the Nb interlayer results in the formation of ternary alloy (Nb,Ti)Si-2 in the C40 crystallographic structure adjacent to the Si substrate. Depending on the nature of the Si substrates and/or the amount of the initial Nb, the interfacial C40 (Nb,Ti)Si-2 leads, in turn, to either epitaxial growth of a highly faulted metastable C40 TiSi2 or formation of the desired C54 TiSi2 at a lower temperature than needed for it to form in reference samples with Ti deposited directly on Si. On p-type substrates doped to various concentrations, the Nb also leads to a considerably lower specific contact resistivity than that obtained in the reference samples: a twofold to fourfold reduction in the contact resistivity is found using cross-bridge Kelvin structures in combination with two-dimensional numerical simulation. As C40 (Nb,Ti)Si-2 forms at the interface when an interfacial Nb is present, the interface characterized is likely to represent the one between (Nb,Ti)Si-2 and Si. For the reference samples, the interface studied is between TiSi2 and Si.

  • 4. Abom, A.E.
    et al.
    Haasch, R.T.
    Frederick Seitz Mat. Res. Laboratory, University of Illinois, Urbana, IL 61801, United States.
    Hellgren, N.
    Frederick Seitz Mat. Res. Laboratory, University of Illinois, Urbana, IL 61801, United States.
    Finnegan, N.
    Frederick Seitz Mat. Res. Laboratory, University of Illinois, Urbana, IL 61801, United States.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Eriksson, Mats
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik.
    Characterization of the metal-insulator interface of field-effect chemical sensors2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 12, s. 9760-9768Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The metal-insulator interface of hydrogen-sensitive metal-insulator-semiconductor capacitors, with SiO2 as the insulator and Pt as the metal contact, was discussed. It was found that the difference in hydrogen response between differently prepared devices was explained by a difference in concentration of available adsorption sites. The analysis showed that the concentration of Pt atoms in contact with the oxide affected both the hydrogen response and the metal-oxide adhesion.

  • 5. Adachi, N.
    et al.
    Denysenkov, V. P.
    Khartsev, Sergiy
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Grishin, Alexander M.
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Okuda, T.
    Epitaxial Bi3Fe5O12(001) films grown by pulsed laser deposition and reactive ion beam sputtering techniques2000Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 88, nr 5, s. 2734-2739Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on processing and comparative characterization of epitaxial Bi3Fe5O12 (BIG) films grown onto Gd-3(ScGa)(5)O-12[GSGG,(001)] single crystal using pulsed laser deposition (PLD) and reactive ion beam sputtering (RIBS) techniques. A very high deposition rate of about 0.8 mu m/h has been achieved in the PLD process. Comprehensive x-ray diffraction analyses reveal epitaxial quality both of the films: they are single phase, exclusively (001) oriented, the full width at half maximum of the rocking curve of (004) Bragg reflection is 0.06 deg for PLD and 0.05 deg for RIBS film, strongly in-plane textured with cube-on-cube film-to-substrate epitaxial relationship. Saturation magnetization 4 pi M-s and Faraday rotation at 635 nm were found to be 1400 Gs and -7.8 deg/mu m in PLD-BIG, and 1200 Gs and -6.9 deg/mu m in RIBS-BIG. Ferromagnetic resonance (FMR) measurements performed at 9.25 GHz yielded the gyromagnetic ratio gamma=1.797x10(7) l/s Oe, 1.826x10(7) l/s Oe; the constants of uniaxial magnetic anisotropy were K-u(*)=-8.66x10(4) erg/cm(3), -8.60x10(4) erg/cm(3); the cubic magnetic anisotropy K-1=-2.7x10(3) erg/cm(3),-3.8x10(3) erg/cm(3); and the FMR linewidth Delta H=25 and 34 Oe for PLD and RIBS films correspondingly. High Faraday rotation, low microwave loss, and low coercive field less than or equal to 40 Oe of BIG/GSGG(001) films promise their use in integrated magneto-optic applications.

  • 6.
    Adamczyk, Krzysztof
    et al.
    Department of Materials Science and Engineering, Trondheim, Norway.
    Søndenå, Rune
    Department for Solar Energy, IFE, Kjeller, Norway.
    Stokkan, Gaute
    Sintef Materials and Chemistry, Trondheim, Norway.
    Looney, Erin
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Jensen, Mallory
    Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
    Lai, Barry
    Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, USA.
    Rinio, Markus
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för ingenjörsvetenskap och fysik (from 2013).
    Di Sabatino, Marisa
    Department of Materials Science and Engineering, NTNU, A. Getz vei 2B, NO-7491 Trondheim, Norway.
    Recombination activity of grain boundaries in high-performance multicrystalline Si during solar cell processing2018Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, nr 5, s. 1-6, artikel-id 055705Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, we applied internal quantum efficiency mapping to study the recombination activity of grain boundaries in High Performance Multicrystalline Silicon under different processing conditions. Wafers were divided into groups and underwent different thermal processing, consisting of phosphorus diffusion gettering and surface passivation with hydrogen rich layers. After these thermal treatments, wafers were processed into heterojunction with intrinsic thin layer solar cells. Light Beam Induced Current and Electron Backscatter Diffraction were applied to analyse the influence of thermal treatment during standard solar cell processing on different types of grain boundaries. The results show that after cell processing, most random-angle grain boundaries in the material are well passivated, but small-angle grain boundaries are not well passivated. Special cases of coincidence site lattice grain boundaries with high recombination activity are also found. Based on micro-X-ray fluorescence measurements, a change in the contamination level is suggested as the reason behind their increased activity.

  • 7.
    Agnarsson, Björn
    et al.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Göthelid, Mats
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Olafsson, S.
    Gislason, H. P.
    Karlsson, Ulf O.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik, Materialfysik, MF.
    Influence of initial surface reconstruction on nitridation of Al2O3 (0001) using low pressure ammonia2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 1, s. 013519-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The purpose of this study is to investigate the effect of initial surface reconstruction on the nitridation process of Al2O3 (0001). This was done by exposing differently reconstructed sapphire substrates at different temperatures to low pressure ammonia (NH3). Structural and chemical analysis were carried out using low-electron energy diffraction and x-ray photoelectron spectroscopy. The experiments revealed that using low pressure ammonia (P-NH3 < 1 X 10(-5) Torr), no nitridation takes place on (1x1) unreconstructed surfaces. However, when the unreconstructed surface starts to change to a (root 31 x root 31) R +/- 9 degrees reconstructed surface, with increasing substrate temperature, the nitridation becomes successful. When using the initially reconstructed surface, the nitridation is successful even from the lowest temperature used. These results suggest that the initial surface reconstruction has a major effect on the nitridation process. This kinetic behavior has not been reported before, with most nitridation studies mainly focusing on the effect of surface temperature on the resulting surface morphology, rather than the actual kinetics of the process itself.

  • 8. Ahuja, R.
    et al.
    Arwin, H.
    da Silva, A. F.
    Persson, Clas
    Osorio-Guillen, J. M.
    de Almeida, J. S.
    Araujo, C. M.
    Veje, E.
    Veissid, N.
    An, C. Y.
    Pepe, I.
    Johansson, Börje
    Electronic and optical properties of lead iodide2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, nr 12, s. 7219-7224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.

  • 9.
    Ahuja, R.
    et al.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Da, Silva A.F.
    Da Silva, A.F., Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario de Ondina, 40 210 340 Salvadoor, Ba, Brazil.
    Persson, C.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Osorio-Guillen, J.M.
    Osorio-Guillén, J.M., Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Souza, De Almeida J.
    Souza De Almeida, J., Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Araujo, C.M.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden, Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario de Ondina, 40 210 340 Salvadoor, Ba, Brazil.
    Veje, E.
    Dept. of Electronic Power Eng., Technical University of Denmark, Building 325, DK-2800 Lyngby, Denmark.
    Veissid, N.
    Instituto Nac. de Pesq. Espaciais, LAS, C.P 515, 12 201 970 Sao Jose dos Campos, SP, Brazil.
    An, C.Y.
    Instituto Nac. de Pesq. Espaciais, LAS, C.P 515, 12 201 970 Sao Jose dos Campos, SP, Brazil.
    Pepe, I.
    Instituto de Fisica, Universidade Federal da Bahia, Campus Universitario de Ondina, 40 210 340 Salvadoor, Ba, Brazil, LPCC, College de France, F-75231, Paris, France.
    Johansson, B.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-751 21 Uppsala, Sweden.
    Electronic and optical properties of lead iodide2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, nr 12, s. 7219-7224Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electronic and optical properties of lead iodide were studied experimentally using absorption, transmission, ellipsometry, and theoretically using a full-potential linear muffin-tin-orbital method. The samples were mounted in a closed-cycle helium refrigeration system and studied at temperatures between 10 and 300 K. Band-gap energy of lead iodide was measured as a function of temperature using optical absorption. Calculations showed that there was a small anisotropy in optical properties of lead iodide, and dielectric function calculations agreed well with experiments.

  • 10. Ahuja, R.
    et al.
    Eriksson, O.
    Johansson, Börje
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Electronic and optical properties of BaTiO3 and SrTiO32001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, nr 4, s. 1854-1859Artikel i tidskrift (Refereegranskat)
  • 11.
    Ahuja, R.
    et al.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, P.O. Box 530, SE-751 21 Uppsala, Sweden.
    Ferreira, Da Silva A.
    Ferreira Da Silva, A., Instituto de Física, Universidade Federal da Bahia, Campus Universitario de Ondina, 40 210 340 Salvador, Ba, Brazil.
    Persson, C.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, P.O. Box 530, SE-751 21 Uppsala, Sweden.
    Osorio-Guillen, J.M.
    Osorio-Guillén, J.M., Condensed Matter Theory Group, Department of Physics, Uppsala University, P.O. Box 530, SE-751 21 Uppsala, Sweden.
    Pepe, I.
    Instituto de Física, Universidade Federal da Bahia, Campus Universitario de Ondina, 40 210 340 Salvador, Ba, Brazil.
    Järrendahl, Kenneth
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Lindquist, O.P.A.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Edwards, N.V.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Wahab, Qamar Ul
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Johansson, B.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, P.O. Box 530, SE-751 21 Uppsala, Sweden.
    Optical properties of 4H-SiC2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, nr 3, s. 2099-2103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies. © 2002 American Institute of Physics.

  • 12. Ahuja, R.
    et al.
    Johansson, Börje
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Theoretical prediction of the Cmca phase in Ge under high pressure2001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 89, nr 5, s. 2547-2549Artikel i tidskrift (Refereegranskat)
  • 13.
    Ahuja, Rajeev
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Fysiska institutionen.
    Arwin, H.
    Ferreira da Silva, A.
    Persson, C.
    Osorio-Guillén, J. M.
    Souza de Almeida, J.
    Araujo, C. Moyses
    Veje, E.
    Veissid, N.
    An, C. Y.
    Electronic and optical properties of lead iodide2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 92, s. 7219-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The electronic properties and the optical absorption of lead iodide (PbI2) have been investigated experimentally by means of optical absorption and spectroscopic ellipsometry, and theoretically by a full-potential linear muffin-tin-orbital method. PbI2 has been recognized as a very promising detector material with a large technological applicability. Its band-gap energy as a function of temperature has also been measured by optical absorption. The temperature dependence has been fitted by two different relations, and a discussion of these fittings is given.

  • 14. Ahuja, Rajeev
    et al.
    da Silva, A. F.
    Persson, Clas
    Osorio-Guillen, J. M.
    Pepe, I.
    Jarrendahl, K.
    Lindquist, O. P. A.
    Edwards, N. V.
    Wahab, Q.
    Johansson, Börje
    Optical properties of 4H-SiC2002Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, nr 4, s. 2099-2103Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optical band gap energy and the dielectric functions of n-type 4H-SiC have been investigated experimentally by transmission spectroscopy and spectroscopic ellipsometry and theoretically by an ab initio full-potential linear muffin-tin-orbital method. We present the real and imaginary parts of the dielectric functions, resolved into the transverse and longitudinal photon moment a, and we show that the anisotropy is small in 4H-SiC. The measurements and the calculations fall closely together in a wide range of energies.

  • 15.
    Ahuja, Rajeev
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Persson, Clas
    da Silva, A. F.
    de Almeida, J. S.
    Araujo, C. M.
    Johansson, Börje
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Optical properties of SiGe alloys2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 7, s. 3832-3836Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optical properties of Si1-xGex have been investigated theoretically using a full-potential linear muffin-tin-orbital method. We present the density-of-states as well as the real and imaginary parts of the dielectric function. The calculated dielectric function was found to be in good agreement with the spectroscopic ellipsometry measurements by J. Bahng , J. Phys.: Condens. Matter 13, 777 (2001), and we obtained a static dielectric constant of epsilon(0)=12.19+2.45x in the Si rich regime (xless than or equal to0.5).

  • 16. Aiempanakit, Montri
    et al.
    Aijaz, Asim
    Lundin, Daniel
    Helmersson, Ulf
    Kubart, Tomas
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Understanding the discharge current behavior in reactive high power impulse magnetron sputtering of oxides2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 13, s. 133302-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The discharge current behavior in reactive high power impulse magnetron sputtering (HiPIMS) of Ti-O and Al-O is investigated. It is found that for both metals, the discharge peak current significantly increases in the oxide mode in contrast to the behavior in reactive direct current magnetron sputtering where the discharge current increases for Al but decreases for Ti when oxygen is introduced. In order to investigate the increase in the discharge current in HiPIMS-mode, the ionic contribution of the discharge in the oxide and metal mode is measured using time-resolved mass spectrometry. The energy distributions and time evolution are investigated during the pulse-on time as well as in the post-discharge. In the oxide mode, the discharge is dominated by ionized oxygen, which has been preferentially sputtered from the target surface. The ionized oxygen determines the discharge behavior in reactive HiPIMS.

  • 17.
    Aiempanakit, Montri
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Aijaz, Asim
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Lundin, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Kubart, Tomas
    The Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Understanding the discharge current behavior in reactive high power impulse magnetron sputtering of oxides2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The discharge current behavior in reactive high power impulse magnetron sputtering (HiPIMS) of Ti-O and Al-O is investigated. It is found that for both metals, the discharge peak current significantly increases in the oxide mode in contrast to the behavior in reactive direct current magnetron sputtering where the discharge current increases for Al but decreases for Ti when oxygen is introduced. In order to investigate the increase in the discharge current in HiPIMS-mode, the ionic contribution of the discharge in the oxide and metal mode is measured using time-resolved mass spectrometry. The energy distributions and time evolution are investigated during the pulse-on time as well as in the post-discharge. In the oxide mode, the discharge is dominated by ionized oxygen, which has been preferentially sputtered from the target surface. The ionized oxygen determines the discharge behavior in reactive HiPIMS.

  • 18. Aiempanakit, Montri
    et al.
    Aijaz, Asim
    Lundin, Daniel
    KTH, Skolan för elektro- och systemteknik (EES), Rymd- och plasmafysik.
    Helmersson, Ulf
    Kubart, Tomas
    Understanding the discharge current behavior in reactive high power impulse magnetron sputtering of oxides2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 13, s. 133302-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The discharge current behavior in reactive high power impulse magnetron sputtering (HiPIMS) of Ti-O and Al-O is investigated. It is found that for both metals, the discharge peak current significantly increases in the oxide mode in contrast to the behavior in reactive direct current magnetron sputtering where the discharge current increases for Al but decreases for Ti when oxygen is introduced. In order to investigate the increase in the discharge current in HiPIMS-mode, the ionic contribution of the discharge in the oxide and metal mode is measured using time-resolved mass spectrometry. The energy distributions and time evolution are investigated during the pulse-on time as well as in the post-discharge. In the oxide mode, the discharge is dominated by ionized oxygen, which has been preferentially sputtered from the target surface. The ionized oxygen determines the discharge behavior in reactive HiPIMS.

  • 19. Akabori, M.
    et al.
    Hidaka, S.
    Iwase, H.
    Yamada, S.
    Ekenberg, Ulf
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Fotonik och optik.
    Realization of In0.75Ga0.25As two-dimensional electron gas bilayer system for spintronics devices based on Rashba spin-orbit interaction2012Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 112, nr 11, s. 113711-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Narrow gap InGaAs two-dimensional electron gas (2DEG) bilayer samples are fabricated and confirmed to have good electronic qualities as well as strong Rashba-type spin-orbit interactions (SOIs). The 2DEG systems are realized by molecular beam epitaxy in the form of wide quantum wells (QWs) with thicknesses tQW∼40-120nm modulation doped in both the upper and lower InAlAs barriers. From the Hall measurements, the overall mobility values of μe ∼15 m2/V s are found for the total sheet electron density of ns ∼8 × 1011/cm2, although the ns is distributed asymmetrically as about 1:3 in the upper and lower 2DEGs, respectively. Careful low temperature magneto-resistance analysis gives large SO coupling constants of α ∼20 × 10 -12eV m as well as expected electron effective masses of m*/m0 ∼0.033-0.042 for each bilayer 2DEG spin sub-band. Moreover, the enhancement of α with decrease of tQW is found. The corresponding self-consistent calculation, which suggests the interaction between the bilayer 2DEGs, is carried out and the origin of α enhancement is discussed.

  • 20.
    Al Hilli, Safaa
    et al.
    Göteborg University.
    Al Morfarji, R.
    Göteborg University.
    Klason, P.
    Göteborg University.
    Willander, Magnus
    Göteborg University.
    Gutman, N.
    The Hebrew University of Jerusalem.
    Saar, A.
    The Hebrew University of Jerusalem.
    Zinc oxide nanorods grown on two-dimensional macroporous periodic structures and plane Si as a pH sensor,2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 1, s. 014302-014309Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    pH determination is a strong prerequisite for many biochemical and biological processes. We used two methods, namely, the electrochemical potential method (experimental) and site binding method (theoretical), to study the sensitivity of zinc oxide (ZnO) nanorods grown on two-dimensional macroporous periodic structures (2DMPPS) (p-and n-type) and plane n-type Si substrates for use as an intracellular pH sensing device. The dimension of these nanorods varied in radius between 50 and 300 nm and lengths of 1–10 μm. We found that the sensitivity of ZnO nanorods increases with reductions in size, from 35 mV/pH for D = 300 nm and L = 10 μm, to 58 mV/pH for D = 50 nm and L = 1 μm, using the site binding model. The experimental electrochemical potential difference for the ZnO nanorods working electrode versus Ag/AgCl reference electrode showed a high sensitivity range for ZnO nanorods grown on 2DMPPS n-Si substrate as compared to plane n-Si at room temperature for pH ranging from 4 to 12 in buffer and NaCl solutions

  • 21. Al Hilli, S.M.
    et al.
    Willander, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för teknik och naturvetenskap.
    Öst, Anita
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för biomedicin och kirurgi, Avdelningen för medicinsk cellbiologi.
    Strålfors, Peter
    Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Institutionen för biomedicin och kirurgi, Avdelningen för medicinsk cellbiologi.
    ZnO nanorods as an intracellular sensor for pH measurements2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    ZnO nanorods with 80 nm diameter and 700 nm length and grown on the tip of a borosilicate glass capillary (0.7 μm in diameter) were used to create a highly sensitive pH sensor for monitoring in vivo biological process within single cells. The ZnO nanorods, functionalized by proton H3 O+ and hydroxyl O H- groups, exhibit a pH -dependent electrochemical potential difference versus a AgAgCl microelectrode. The potential difference was linear over a large dynamic range (4-11), which could be understood in terms of the change in surface charge during protonation and deprotonation. These nanoelectrode devices have the ability to enable analytical measurements in single living cells and have the capability to sense individual chemical species in specific locations within a cell. © 2007 American Institute of Physics.

  • 22. Alarco, J A
    et al.
    Brorsson, G
    Olin, Håkan
    Department of Physics, Chalmers University of Technology/University of Göteborg.
    Olsson, E
    Early stages of growth of YBa2Cu3O7− high Tc superconducting films on (001) Y-ZrO2 substrates1994Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 75, s. 3202-3204Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Theearly stages of growth of high quality YBa2Cu3O7− (YBCO) filmsgrown on (001) Y-ZrO2 (YSZ) substrates by pulsed laser depositionhave been studied using a combination of atomic force microscopyand transmission electron microscopy. A one unit cell thick YBCOlayer and relatively large CuO particles formed in the initialstages. Additional YBCO grew on top of the first layerin the form of one or a few unit cellhigh c-axis oriented islands about 30 nm in diameter. Therounded islands subsequently coalesced into faceted domains. Elongated Y2BaCuO5 particlesnucleated after the first layer of YBCO. A highly texturedBaZrO3 layer formed between the YSZ and the YBCO witha cube-on-cube dominant orientation relationship with respect to the YBCOfilm. Journal of Applied Physics is copyrighted by The American Institute of Physics.

  • 23. Alfieri, G.
    et al.
    Monakhov, E. V.
    Svensson, B. G.
    Hallén, Anders.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Materialfysik.
    Defect energy levels in hydrogen-implanted and electron-irradiated n-type 4H silicon carbide2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, nr 11Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using deep level transient spectroscopy (DLTS), we have studied the energy position and thermal stability of deep levels in nitrogen doped 4H-SiC epitaxial layers after 1.2 MeV proton implantation and 15 MeV electron irradiation. Isochronal annealing was performed at temperatures from 100 to 1200 degrees C in steps of 50 degrees C. The DLTS measurements, which were carried out in the temperature range from 120 to 630 K after each annealing step, reveal the presence of ten electron traps located in the energy range of 0.45-1.6 eV below the conduction band edge (E-c). Of these ten levels, three traps at 0.69, 0.73, and 1.03 eV below E-c, respectively, are observed only after proton implantation. Dose dependence and depth profiling studies of these levels have been performed. Comparing the experimental data with computer simulations of the implantation and defects profiles, it is suggested that these three new levels, not previously reported in the literature, are hydrogen related. In particular, the E-c-0.73 eV level displays a very narrow depth distribution, confined within the implantation profile, and it originates most likely from a defect involving only one H atom.

  • 24. Alfieri, G.
    et al.
    Monakhov, E. V.
    Svensson, B. G.
    Linnarsson, Margareta K.
    KTH, Skolan för informations- och kommunikationsteknik (ICT), Mikroelektronik och tillämpad fysik, MAP.
    Annealing behavior between room temperature and 2000 degrees C of deep level defects in electron-irradiated n-type 4H silicon carbide2005Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, nr 4Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The annealing behavior of irradiation-induced defects in 4H-SiC epitaxial layers grown by chemical-vapor deposition has been systematically studied by means of deep level transient spectroscopy (DLTS). The nitrogen-doped epitaxial layers have been irradiated with 15-MeV electrons at room temperature and an isochronal annealing series from 100 to 2000 degrees C has been performed. The DLTS measurements, which have been carried out in the temperature range from 120 to 630 K after each annealing step, revealed the presence of six electron traps located in the energy range of 0.45-1.6 eV below the conduction-band edge (E-c). The most prominent and stable ones occur at E-c-0.70 eV (labeled Z(1/2)) and E-c-1.60 eV(EH6/7). After exhibiting a multistage annealing process over a wide temperature range, presumably caused by reactions with migrating defects, a significant fraction of both Z(1/2) and EH6/7 (25%) still persists at 2000 degrees C and activation energies for dissociation in excess of 8 and similar to 7.5 eV are estimated for Z(1/2) and EH6/7, respectively. On the basis of these results, the identity of Z(1/2) and EH6/7 is discussed and related to previous assignments in the literature.

  • 25.
    Al-Hamadandy, Raied
    et al.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Goss, J.P.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Briddon, P.R.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Mojarad, Shahin A.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Al-Hadidi, Meaad
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    O'Neill, A.G.
    School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Oxygen vacancy migration in compressively strained SrTiO32013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 2Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The intrinsic properties of strontium titanate render it promising in applications such as gate dielectrics and capacitors. However, there is growing evidence that oxygen vacancies significantly impact upon its use, with the diffusion and deep donor level of the oxygen vacancy leading to electrical leakage. Where grown epitaxially on a lattice mismatched substrate, SrTiO 3 undergoes bi-axial strain, altering its crystal structure and electronic properties. In this paper, we present the results of first-principles simulations to evaluate the impact of strain in a (001) plane upon the migration of oxygen vacancies. We show that in the range of strains consistent with common substrate materials, diffusion energies in different directions are significantly affected, and for high values of strain may be altered by as much as a factor of two. The resulting diffusion anisotropy is expected to impact upon the rate at which oxygen vacancies are injected into the films under bias, a critical factor in the leakage and resistive switching seen in this material

  • 26.
    Al-Hamadany, R.
    et al.
    Newcastle University.
    Goss, J.P.
    Newcastle University.
    Briddon, P.R.
    Newcastle University.
    Mojarad, S.A.
    Newcastle University.
    O'Neill, A.G.
    Newcastle University.
    Rayson, Mark
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    Impact of tensile strain on the oxygen vacancy migration in SrTiO3: Density functional theory calculations2013Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, nr 22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Strontium titanate is a promising dielectric material for device applications including capacitors and gate dielectrics. However, oxygen vacancies, which are inevitable donor defects mobile under bias at room temperature, lead to undesirable leakage current in SrTiO3 thin films. Epitaxially grown SrTiO3 on lattice mismatched substrates leads to strained SrTiO3, inducing structural phase transitions from a cubosymmetric non-ferroelectric geometry to tetragonal and orthorhombic structures, depending upon the sign of the strain. In this study, density functional calculations have been performed to determine the impact of isotropic biaxial tensile strain in a (001) plane upon the phase of SrTiO3 and the activation energy for the migration of oxygen vacancies in such strained SrTiO3. The phase transition of the host material yields anisotropy in oxygen vacancy diffusion for diffusion within and between planes parallel to the strain. We found a general reduction in the barrier for diffusion within and normal to the plane of tensile strain. The inter-plane diffusion barrier reduces up to 25% at high values of strain. The variation in the barrier corresponding to in-plane diffusion is smaller in comparison to inter-plane diffusion. Finally, we reflect upon how the interplay between lattice strain with native defects plays a crucial role in the conduction mechanism of thin film, strained SrTiO3

  • 27. Ali, MP
    et al.
    Tove, PA
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Fasta tillståndets elektronik.
    Ibrahim, M
    Barrier height of evaporated manganese contacts to silicon1979Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 50, nr 11, s. 7250-Artikel i tidskrift (Refereegranskat)
  • 28. Alkhadi, H.S.
    et al.
    Tran, Tuan
    Department of Electronic Materials Engineering, Research School of Physics and Engineering, The Australian National University, Canberra, Australia.
    Kremer, F.
    Williams, J.S.
    The influence of capping layers on pore formation in Ge during ion implantation2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 120, nr 21, artikel-id 215706Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ion induced porosity in Ge has been investigated with and without a cap layer for two ion species, Ge and Sn, with respect to ion fluence and temperature. Results without a cap are consistent with a previous work in terms of an observed ion fluence and temperature dependence of porosity, but with a clear ion species effect where heavier Sn ions induce porosity at lower temperature (and fluence) than Ge. The effect of a cap layer is to suppress porosity for both Sn and Ge at lower temperatures but in different temperatures and fluence regimes. At room temperature, a cap does not suppress porosity and results in a more organised pore structure under conditions where sputtering of the underlying Ge does not occur. Finally, we observed an interesting effect in which a barrier layer of a-Ge that is denuded of pores formed directly below the cap layer. The thickness of this layer (∼ 8 nm) is largely independent of ion species, fluence, temperature, and cap material, and we suggest that this is due to viscous flow of a-Ge under ion irradiation and wetting of the cap layer to minimize the interfacial free energy.

  • 29.
    Alling, Björn
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Marten, Tobias
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Abrikosov, Igor
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Karimi, A.
    Swiss Federal Institute of Technology Lausanne, Switzerland.
    Comparison of thermodynamic properties of cubic Cr 1-x Al x N and Ti 1-x Al x N from first-principles calculations2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, nr 044314Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In order to investigate the stability of the cubic phase of Cr1−xAlxN at high AlN content, first principles calculations of magnetic properties, lattice parameters, electronic structure, and mixing enthalpies of the system were performed. The mixing enthalpy was calculated on a fine concentration mesh to make possible the accurate determination of its second concentration derivative. The results are compared to calculations performed for the related compound Ti1−xAlxN and with experiments. The mixing enthalpy is discussed in the context of isostructural spinodal decomposition. It is shown that the magnetism is the key to understand the difference between the Cr- and Ti-containing systems. Cr1−xAlxN turns out to be more stable against spinodal decomposition than Ti1−xAlxN, especially for AlN-rich samples which are of interest in cutting tools applications.

  • 30.
    Almer, J.
    et al.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Lienert, U.
    Advanced Photon Source (APS), Argonne National Laboratory, Argonne.
    Peng, R.L.
    Linköping universitet.
    Schlauer, C.
    Linköping universitet.
    Odén, Magnus
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Strain and texture analysis of coatings using high-energy x-rays2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 1, s. 697-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed

  • 31.
    Almer, J.
    et al.
    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois.
    Lienert, U
    Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois.
    Peng, Ru
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Schlauer, Christian
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Engineering Materials Luleå University of Technology.
    Strain and texture analysis of coatings using high-energy x-rays2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, nr 1, s. 697-702Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We investigate the internal strain and crystallographic orientation (texture) in physical-vapor deposited metal nitride coatings of TiN and CrN. A high-energy diffraction technique is presented that uses synchrotron x rays and an area detector, and which allows the strain and intensity distributions of multiple crystallographic planes to be measured by a single x-ray exposure. Unique texture states and nonlinear sin2 ψ strain distributions are observed for all coatings investigated. Quantitative analysis indicates that existing micromechanical models can reasonably predict strain and corresponding stress for mixed-hkl reflections but are inadequate for fully describing measured data. Alternative mechanisms involving deposition-induced defects are proposed.

  • 32.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Khranovskyy, Volodymyr
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Iandolo, Donata
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Influence of ZnO seed layer precursor molar ratio on the density of interface defects in low temperature aqueous chemically synthesized ZnO nanorods/GaN light-emitting diodes2016Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, nr 16, s. 165702-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Low temperature aqueous chemical synthesis (LT-ACS) of zinc oxide (ZnO) nanorods (NRs) has been attracting considerable research interest due to its great potential in the development of light-emitting diodes (LEDs). The influence of the molar ratio of the zinc acetate (ZnAc): KOH as a ZnO seed layer precursor on the density of interface defects and hence the presence of non-radiative recombination centers in LT-ACS of ZnO NRs/GaN LEDs has been systematically investigated. The material quality of the as-prepared seed layer as quantitatively deduced by the X-ray photoelectron spectroscopy is found to be influenced by the molar ratio. It is revealed by spatially resolved cathodoluminescence that the seed layer molar ratio plays a significant role in the formation and the density of defects at the n-ZnO NRs/p-GaN heterostructure interface. Consequently, LED devices processed using ZnO NRs synthesized with molar ratio of 1:5M exhibit stronger yellow emission (similar to 575 nm) compared to those based on 1:1 and 1:3M ratios as measured by the electroluminescence. Furthermore, seed layer molar ratio shows a quantitative dependence of the non-radiative defect densities as deduced from light-output current characteristics analysis. These results have implications on the development of high-efficiency ZnO-based LEDs and may also be helpful in understanding the effects of the ZnO seed layer on defect-related non-radiative recombination. Published by AIP Publishing.

  • 33.
    Alnoor, Hatim
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap. Linköpings universitet, Tekniska fakulteten.
    Savoyant, Adrien
    Aix Marseille University, France.
    Liu, Xianjie
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Ytors Fysik och Kemi. Linköpings universitet, Tekniska fakulteten.
    Pozina, Galia
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Willander, Magnus
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    Nur, Omer
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Fysik och elektroteknik. Linköpings universitet, Tekniska fakulteten.
    An effective low-temperature solution synthesis of Co-doped [0001]-oriented ZnO nanorods2017Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, nr 21, artikel-id 215102Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We demonstrate an efficient possibility to synthesize vertically aligned pure zinc oxide (ZnO) and Co-doped ZnO nanorods (NRs) using the low-temperature aqueous chemical synthesis (90 degrees C). Two different mixing methods of the synthesis solutions were investigated for the Co-doped samples. The synthesized samples were compared to pure ZnO NRs regarding the Co incorporation and crystal quality. Electron paramagnetic resonance (EPR) measurements confirmed the substitution of Co2+ inside the ZnO NRs, giving a highly anisotropic magnetic Co2+ signal. The substitution of Zn2+ by Co2+ was observed to be combined with a drastic reduction in the core-defect (CD) signal (g similar to 1.956) which is seen in pure ZnO NRs. As revealed by the cathodoluminescence (CL), the incorporation of Co causes a slight red-shift of the UV peak position combined with an enhancement in the intensity of the defect-related yellow-orange emission compared to pure ZnO NRs. Furthermore, the EPR and the CL measurements allow a possible model of the defect configuration in the samples. It is proposed that the as-synthesized pure ZnO NRs likely contain Zn interstitial (Zn-i(+)) as CDs and oxygen vacancy (V-O) or oxygen interstitial (O-i) as surface defects. As a result, Co was found to likely occupy the Zn-i(+), leading to the observed CDs reduction and hence enhancing the crystal quality. These results open the possibility of synthesis of highly crystalline quality ZnO NRs-based diluted magnetic semiconductors using the low-temperature aqueous chemical method. Published by AIP Publishing.

  • 34. Al-Zoubi, N.
    et al.
    Johansson, Börje
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Nilson, G.
    Vitos, Levente
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    The Bain path of paramagnetic Fe-Cr based alloys2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, nr 1, s. 013708-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.

  • 35.
    Al-Zoubi, Noura
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Johansson, Börje
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    Nilson, G.
    Uddeholms AB, Hagfors, Sweden.
    Vitos, Levente
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
    The bain path of paramagnetic Fe-Cr based alloys2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, nr 1, s. 013708-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.

  • 36.
    Anasori, Babak
    et al.
    Drexel University, PA 19104 USA; Drexel University, PA 19104 USA.
    Dahlqvist, Martin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Halim, Joseph
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten. Drexel University, PA 19104 USA.
    Ju Moon, Eun
    Drexel University, PA 19104 USA.
    Lu, Jun
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Hosler, Brian C.
    Drexel University, PA 19104 USA.
    Caspi, Elad N.
    Drexel University, PA 19104 USA; Nucl Research Centre Negev, Israel.
    May, Steven J.
    Drexel University, PA 19104 USA.
    Hultman, Lars
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Eklund, Per
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Rosén, Johanna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik. Linköpings universitet, Tekniska fakulteten.
    Barsoum, Michel W.
    Drexel University, PA 19104 USA.
    Experimental and theoretical characterization of ordered MAX phases Mo2TiAlC2 and Mo2Ti2AlC32015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, nr 9, s. 094304-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Herein, we report on the phase stabilities and crystal structures of two newly discovered ordered, quaternary MAX phases-Mo2TiAlC2 and Mo2Ti2AlC3-synthesized by mixing and heating different elemental powder mixtures of mMo:(3-m) Ti:1.1Al:2C with 1.5 less than= m less than= 2.2 and 2Mo: 2Ti:1.1Al:2.7C to 1600 degrees C for 4 h under Ar flow. In general, for m greater than= 2 an ordered 312 phase, (Mo2Ti) AlC2, was the majority phase; for mless than 2, an ordered 413 phase (Mo2Ti2)AlC3, was the major product. The actual chemistries determined from X-ray photoelectron spectroscopy (XPS) are Mo2TiAlC1.7 and Mo2Ti1.9Al0.9C2.5, respectively. High resolution scanning transmission microscopy, XPS and Rietveld analysis of powder X-ray diffraction confirmed the general ordered stacking sequence to be Mo-Ti-Mo-Al-Mo-Ti-Mo for Mo2TiAlC2 and Mo-Ti-Ti-Mo-Al-Mo-Ti-Ti-Mo for Mo2Ti2AlC3, with the carbon atoms occupying the octahedral sites between the transition metal layers. Consistent with the experimental results, the theoretical calculations clearly show that M layer ordering is mostly driven by the high penalty paid in energy by having the Mo atoms surrounded by C in a face-centered configuration, i.e., in the center of the Mn+1Xn blocks. At 331 GPa and 367 GPa, respectively, the Youngs moduli of the ordered Mo2TiAlC2 and Mo2Ti2AlC3 are predicted to be higher than those calculated for their ternary end members. Like most other MAX phases, because of the high density of states at the Fermi level, the resistivity measurement over 300 to 10K for both phases showed metallic behavior. (C) 2015 AIP Publishing LLC.

  • 37.
    Andersson, Göran
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Bäckström, Gunnar
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    A high-pressure cell for electrical resistance measurements at hydrostatic pressures up to 8 GPa: Results for Bi, Ba, Ni, and Si1989Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 65, nr 10, s. 3943-3950Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A modified Bridgman anvil high-pressure device, capable of producing hydrostatic pressures up to 8 GPa (80 kbar), was designed and built. The size of the pressure chamber (10 mm in diameter) allows the use of large specimens and simple experimental procedures. Experimental results show that hydrostatic conditions are necessary if accurate quantitative information is desired about the electrical properties of materials under pressure. Accurate data on resistance (and resistivity) versus pressure at 294 K are given for Bi, Ba, Ni, and Si. The initial pressure coefficients of R were d(ln R)dP=0.13, −7.6×10−2, −2.0×10−2, and −0.26 GPa−1, respectively. Barium has a resistance minimum near 0.9 GPa. For Bi we observe sharp transitions at 2.55, 2.7, and 7.7 GPa, and for Ba at 5.55 GPa, but we cannot verify the existence of a transition in Ba near 7 GPa. Neither do we confirm the phase transformation in Ni recently reported to occur above 2.5 GPa. For Si, R(P) agrees very well with a theoretical function calculated from the change in band gap and electron mobility with pressure.

  • 38.
    Andersson, Jon M.
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Wallin, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Münger, Peter
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Helmersson, Ulf
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Energy distributions of positive and negative ions during magnetron sputtering of an Al target in Ar/O2 mixtures2006Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 100, nr 3, s. Art. No. 033305 AUG 1 2006-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The ion flux obtained during reactive magnetron sputtering of an Al target in Ar/O2 gas mixtures was studied by energy-resolved mass spectrometry, as a function of the total and O2 partial pressures. The positive ions of film-forming species exhibited bimodal energy distributions, both for direct current and radio frequency discharges, with the higher energy ions most likely originating from sputtered neutrals. For the negative oxygen ions a high-energy peak was observed, corresponding to ions formed at the target surface and accelerated towards the substrate over the sheath potential. As the total pressure was increased the high-energy peaks diminished due to gas-phase scattering. Based on these results, the role of energetic bombardment for the phase constituent of alumina thin films are discussed.

  • 39.
    Andersson, Mattias
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Mueller, Christian
    Esfera UAB.
    Badada, Bekele H
    University of Cincinnati.
    Zhang, Fengling
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Wuerful, Uli
    Fraunhofer Institute Solar Energy Syst ISE.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Mobility and fill factor correlation in geminate recombination limited solar cells2011Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, nr 2, s. 024509-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Empirical data for the fill factor as a function of charge carrier mobility for two different polymer: fullerene systems is presented and analyzed. The results indicate that charge extraction depth limitations and space charge effects are inconsistent with the observed behavior, and the decrease in the fill factor is, instead, attributed to the field-dependent charge separation and geminate recombination. A solar cell photocurrent limited by the Onsager-Braun charge transfer exciton dissociation is shown to be able to accommodate the experimental observations. Charge dissociation limited solar cells always benefit from increased mobilities, and the negative contribution from the reduced charge separation is shown to be much more important for the fill factor in these material systems than any adverse effects from charge carrier extraction depth limitations or space charge effects due to unbalanced mobilities. The logarithmic dependence of the fill factor on the mobility for such a process is also shown to imply that simply increasing the mobilities is an impractical way to reach very high fill factors under these conditions since unrealistically high mobilities are required. A more controlled morphology is, instead, argued to be necessary for high performance.

  • 40.
    Andersson, Sebastian
    et al.
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Korenivski, Vladislav
    KTH, Skolan för teknikvetenskap (SCI), Tillämpad fysik, Nanostrukturfysik.
    Exchange coupling and magnetoresistance in CoFe/NiCu/CoFe spin valves near the Curie point of the spacer2010Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 107, nr 9, s. 09D711-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermal control of exchange coupling between two strongly ferromagnetic layers through a weakly ferromagnetic Ni-Cu spacer and the associated magnetoresistance is investigated. The spacer, having a Curie point slightly above room temperature, can be cycled between its paramagnetic and ferromagnetic states by varying the temperature externally or using joule heating. It is shown that the giant magnetoresistance vanishes due to a strong reduction in the mean free path in the spacer at above similar to 30% Ni concentration-before the onset of ferromagnetism. Finally, a device is proposed which combines thermally controlled exchange coupling and large magnetoresistance by separating the switching and the readout elements.

  • 41. Andersson, Viktor
    et al.
    Persson, Nils-Krister
    Högskolan i Borås, Institutionen Textilhögskolan.
    Inganäs, Olle
    Comparative study of organic thin film tandem solar cells in alternative geometries2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, nr 12, s. 6-Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Optical modelling of one folded tandem solar cell and four types of stacked tandem solar cells has been performed, using the finite element method and the transfer matrix method for the folded cell and the stacked cells, respectively. The results are analysed by comparing upper limits for short circuit currents and power conversion efficiencies. In the case of serial connected tandems all of the five cell types may be compared, and we find that the folded cells are comparable to stacked tandem cells in terms of currents and power conversion efficiencies.

  • 42.
    Andersson, Viktor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Plasma och beläggningsfysik. Linköpings universitet, Tekniska högskolan.
    Persson, Nils-Krister
    School of Engineering, Swedish School of Textiles, University College of Borås, SE-501 90 Borås, Sweden.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Comparative study of organic thin film tandem solar cells in alternative geometries2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, nr 12, s. 124508-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Optical modeling of one folded tandem solar cell and four types of stacked tandem solar cells has been performed using the finite element method and the transfer matrix method for the folded cell and the stacked cells, respectively. The results are analyzed by comparing upper limits for short circuit currents and power conversion efficiencies. In the case of serial connected tandems all of the five cell types may be compared, and we find that the folded cells are comparable to stacked tandem cells in terms of currents and power conversion efficiencies.

  • 43.
    Andersson, Viktor
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Tvingstedt, Kristofer
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Biomolekylär och Organisk Elektronik. Linköpings universitet, Tekniska högskolan.
    Optical modeling of a folded organic solar cell2008Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, nr 9, s. 094520-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The optical behavior of a reflective tandem solar cell (V cell) is modeled by means of finite element method (FEM) simulations. The absorption of solar light in the active material as well as in both electrode layers is calculated. The FEM solves the electromagnetic wave equation on the entire defined geometry, resulting in the consideration of interference effects, as well as effects of refraction and reflection. Both single cells and tandem cells are modeled and confirmed to be in accordance with reflectance measurements. Energy dissipation in the active layers is studied as a function of layer thickness and folding angle, and the simulations clearly display the advantage of the light trapping feature of folded cells. This is especially prominent in cells with thinner active layers, where folding induces absorption in the active layer equivalent to that of much thicker cells.

  • 44.
    Araujo, Rafael B.
    et al.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    de Almeida, J. S.
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    da Silva, A. Ferreira
    Univ Fed Bahia, Inst Fis, Salvador, BA, Brazil..
    Ahuja, Rajeev
    Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
    Insights in the electronic structure and redox reaction energy in LiFePO4 battery material from an accurate Tran-Blaha modified Becke Johnson potential2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, nr 12, artikel-id 125107Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main goals of this paper are to investigate the accuracy of the Tran-Blaha modified Becke Johnson (TB-mBJ) potential to predict the electronic structure of lithium iron phosphate and the related redox reaction energy with the lithium deintercalation process. The computed electronic structures show that the TB-mBJ method is able to partially localize Fe-3d electrons in LiFePO4 and FePO4 which usually is a problem for the generalized gradient approximation (GGA) due to the self interaction error. The energy band gap is also improved by the TB-mBJ calculations in comparison with the GGA results. It turned out, however, that the redox reaction energy evaluated by the TB-mBJ technique is not in good agreement with the measured one. It is speculated that this disagreement in the computed redox energy and the experimental value is due to the lack of a formal expression to evaluate the exchange and correlation energy. Therefore, the TB-mBJ is an efficient method to improve the prediction of the electronic structures coming form the standard GGA functional in LiFePO4 and FePO4. However, it does not appear to have the same efficiency for evaluating the redox reaction energies for the investigated system.

  • 45. Arzbacher, S.
    et al.
    Amann, Peter
    Stockholms universitet, Naturvetenskapliga fakulteten, Fysikum.
    Weidenfeller, B.
    Loerting, T.
    Ostermann, A.
    Petrasch, J.
    Tomography based numerical simulation of the demagnetizing field in soft magnetic composites2015Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, nr 16, artikel-id 163905Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The magneto-static behaviour of soft magnetic composites (SMCs) is investigated using tomography based direct numerical simulation. The microgeometry crucially affects the magnetic properties of the composite since a geometry dependent demagnetizing field is established inside the composite, which lowers the magnetic permeability. We determine the magnetic field information inside the SMC using direct numerical simulation of the magnetic field based on high resolution micro-computed tomography data of the SMC's microstructure as well as artificially generated data made of statistically homogeneous systems of identical fully penetrable spheres and prolate spheroids. Quasi-static electromagnetic behaviour and linear material response are assumed. The 3D magnetostatic Maxwell equations are solved using Whitney finite elements. Simulations show that clustering and percolation behaviour determine the demagnetizing factor of SMCs rather than the particle shape. The demagnetizing factor correlates with the slope of a 2-point probability function at its origin, which is related to the specific surface area of the SMC. Comparison with experimental results indicates that the relatively low permeability of SMCs cannot be explained by demagnetizing effects alone and suggests that the permeability of SMC particles has to be orders of magnitude smaller than the bulk permeability of the particle material.

  • 46. Asghar, M.
    et al.
    Hussain, I.
    Noor, N.
    Iqbal, F.
    Wahab, Qamar Ul
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Bhatti, A.
    Properties of dominant electron trap center in n-type SiC epilayers by means of deep level transient spectroscopy2007Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, nr 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Characterization of dominant electron trap in as-grown SiC epilayers has been carried out using deep level transient spectroscopy. Two electron traps E1 and Z1 at Ec-0.21 and Ec-0.61 are observed, respectively, Z1 being the dominant level. Line shape fitting, capture cross section, and insensitivity with doping concentration have revealed interesting features of Z1 center. Spatial distribution discloses that the level is generated in the vicinity of epilayers/substrate interface and the rest of the overgrown layers is defect-free. Owing to the Si-rich growth conditions, the depth profile of Z1 relates it to carbon vacancy. The alpha particle irradiation transforms Z1 level into Z 1/Z2 center involving silicon and carbon vacancies. Isochronal annealing study further strengthens the proposed origin of the debated level. © 2007 American Institute of Physics.

  • 47.
    Ashkenov, N.
    et al.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Mbenkum, B.N.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Bundesmann, C.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Riede, V.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Lorenz, M.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Spemann, D.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Kaidashev, E.M.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany, Rostov State University, Mech./Appl. Math. Research Institute, 200/1 Stachky Avenue, Rostov-on-Don 344090, Russian Federation.
    Kasic, A.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Schubert, M.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Grundmann, M.
    Universität Leipzig, Fak. F. Phys. and Geowissenschaften, Inst. F. Experimentelle Physik II, Linnéstrasse 5, 04103 Leipzig, Germany.
    Wagner, G.
    Inst. F. Nichtklassische Chem. e.V., Universität Leipzig, Permoserstraße 15, 04318 Leipzig, Germany.
    Neumann, H.
    Inst. F. O. e.V., Permoserstrasse 15, 04303 Leipzig, Germany.
    Darakchieva, Vanya
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Arwin, Hans
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad optik.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik.
    Infrared dielectric functions and phonon modes of high-quality ZnO films2003Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 93, nr 1, s. 126-133Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study was performed on the phonon modes and infrared dielectric functions of high-quality ZnO thin films. The pulsed laser deposition technique was used to deposit the ZnO films on c-plane sapphire substrates and were investigated by high-resolution transmission electron microscopy, high-resolution x-ray diffraction and Rutherford backscattering experiments. The accurate long-wavelength dielectric constant limits of the films were also obtained and were compared with near-band-gap index-of-refraction data upon the Lyddane-Sachs-Teller relation for both film and bulk samples. It was found that the phonon modes of the film were highly consistent with those of the bulk sample.

  • 48.
    Ashraf, H.
    et al.
    Radboud University Nijmegen.
    Imran Arshad, M.
    Islamia University Bahawalpur.
    Muniza Faraz, Sadia
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Ul Wahab, Qamar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Hageman, P. R.
    Radboud University Nijmegen.
    Asghar, M.
    Islamia University Bahawalpur.
    Study of electric field enhanced emission rates of an electron trap in n-type GaN grown by hydride vapor phase epitaxy2010Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, nr 10Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electric field-enhanced emission of electrons from a deep level defect in GaN grown by hydride vapor phase epitaxy has been studied. Using the field dependent mode of conventional deep level transient spectroscopy (DLTS), several frequency scans were performed keeping applied electric field (12.8-31.4 MV/m) and sample temperature (300-360 K) constant. Arrhenius plots of the resultant data yielded an activation energy of the electron trap E ranging from E-c -0.48 +/- 0.02 eV to E-c-0.35 +/- 0.02 eV, respectively. The extrapolation of the as-measured field dependent data (activation energy) revealed the zero-field emission energy (pure thermal activation energy) of the trap to be 0.55 +/- 0.02 eV. Various theoretical models were applied to justify the field-enhanced emission of the carriers from the trap. Eventually it was found that the Poole-Frenkel model associated with a square well potential of radius r=4.8 nm was consistent with the experimental data, and, as a result, the trap is attributed to a charged impurity. Earlier, qualitative measurements like current-voltage (I-V) and capacitance-voltage (C-V) measurements were performed, and screening parameters of the device were extracted to ascertain the reliability of DLTS data.

  • 49.
    Ashwin, M.J.
    et al.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Pritchard, R.E.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Newman, R.C.
    Interdisciplinary Research Centre for Semiconductor Materials, The Blackett Laboratory, Imperial College of Science, Technology and Medicine, London.
    Joyce, T.B.
    Department of Materials Science and Engineering, Liverpool University.
    Bullough, T.J.
    Department of Materials Science and Engineering, Liverpool University.
    Wagner, J.
    Fraunhofer-Institut für Angewandte Festkörperphysik, Tullastrasse 72, D-79108 Freiburg.
    Jeynes, C.
    Department of Electronic and Electrical Engineering, University of Surrey, Guildford.
    Breuer, S.J.
    Department of Physics, University of Exeter.
    Jones, R.
    Department of Physics, University of Exeter.
    Briddon, P.R.
    Department of Physics, University of Newcastle.
    Öberg, Sven
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Matematiska vetenskaper.
    The bonding of CAs acceptors in InxGa1-xAs grown by chemical beam epitaxy using carbon tetrabromide as the source of carbon1996Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 80, nr 12, s. 6754-6760Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    InxGa1-xAs layers (0≤x≤0.37) doped with carbon (>1020 cm-3) were grown on semi-insulating GaAs substrates by chemical beam epitaxy using carbon tetrabromide (CBr4) as the dopant source. Hall measurements imply that all of the carbon was present as CAs for values x up to 0.15. The C acceptors were passivated by exposing samples to a radio frequency hydrogen plasma for periods of up to 6 h. The nearest-neighbor bonding configurations of CAs were investigated by studying the nondegenerate antisymmetric hydrogen stretch mode (A-1 symmetry) and the symmetric XH mode (A+1 symmetry) of the H-CAs pairs using IR absorption and Raman scattering, respectively. Observed modes at 2635 and 450 cm-1 had been assigned to passivated Ga4CAs clusters. New modes at 2550 and 430 cm-1 increased in strength with increasing values of x and are assigned to passivated InGa3CAs clusters. These results were compared with ab initio local density functional theory. Modes due to AlInGaCAs clusters were detected in samples containing grown in Al and In. These results demonstrate that for InGaAs, CBr4 is an efficient C doping source since both In-CAs bonds as well as Ga-CAs bonds are formed, whereas there is no evidence for the formation of In-CAs bonds in samples doped with C derived from trimethylgallium or solid sources

  • 50. Asplund, C.
    et al.
    Mogg, S.
    Plaine, G.
    Salomonsson, F.
    Chitica, N.
    Hammar, Mattias
    KTH, Tidigare Institutioner                               , Mikroelektronik och informationsteknik, IMIT.
    Doping-induced losses in AlAs/GaAs distributed Bragg reflectors2001Ingår i: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 90, nr 2, s. 794-800Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied n- and p-type doping-induced performance degradation of AlAs/GaAs distributed Bragg reflectors (DBRs) for applications in vertical cavity lasers (VCLs). Based on high-accuracy optical reflectance and triple-axis x-ray diffraction measurements on a variety of differently doped DBR structures grown by metalorganic vapor-phase epitaxy, a fitting procedure was employed to extract the doping-dependent optical loss. A striking observation is that the reflectance of these DBRs is much more sensitive to n- than p-type doping incorporation. While in the latter case the loss can be well accounted for by intervalence-band and free-carrier absorption, additional loss mechanisms must be considered for n-type DBRs. We relate the losses to doping-enhanced interdiffusion effects resulting in increased interface scattering. These findings should have important consequences for the design of VCLs, demonstrating the importance of reduced n-type doping concentrations and/or growth temperatures, or the application of alternative device concepts, e.g., employing intracavity contacts.

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