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  • 51.
    Ritchie, Andrew
    et al.
    University of Saskatchewan, Saskatoon, SK, Canada.
    Eger, Shaylin
    University of Saskatchewan, Saskatoon, SK, Canada.
    Wright, Chelsey
    Canadian Light Source, Saskatoon, SK, Canada.
    Chelladurai, Saniel
    University of Saskatchewan, Saskatoon, SK, Canada.
    Borrowman, Cuyler
    University of Saskatchewan, Saskatoon, SK, Canada.
    Olovsson, Weine
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Magnuson, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Verma, Jai
    University of Notre Dame, IN, USA.
    Jena, Debdeep
    Univeristy of Notre Dame, IN, USA.
    Grace Xing, Huili
    University of Notre Dame, IN, USA.
    Duboc, Christian
    Osemi Canada Inc., Sherbrooke, Quebec, Canada.
    Urquhart, Stephen
    University of Saskatchewan, Saskatoon, SK, Canada.
    Strain sensitivity in the nitrogen 1s NEXAFS spectra of gallium nitride2014In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 316, p. 232-236Article in journal (Refereed)
    Abstract [en]

    The nitrogen 1s near edge X-ray absorption fine structure (NEXAFS) of gallium nitride (GaN) shows astrong natural linear dichroism that arises from its anisotropic wurtzite structure. An additional spectro-scopic variation arises from lattice strain in epitaxially grown GaN thin films. This variation is directlyproportional to the degree of strain for some spectroscopic features. This strain variation is interpretedwith the aid of density functional theory calculations.

  • 52.
    Sangiovanni, Davide Giuseppe
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Copper adatom, admolecule transport, and island nucleation on TiN(0 0 1) via ab initio molecular dynamics2018In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 50, p. 180-189Article in journal (Refereed)
    Abstract [en]

    Density-functional ab initio molecular dynamics (AIMD) simulations are carried out to determine Cu adatom and admolecule transport properties as a function of temperature, as well as atomistic processes leading to formation of Cu/TiN(0 0 1) islands at 350 K. At very low temperatures T ≤ 200 K, Cu adatoms (Cuad) migrate among favored fourfold-hollow surface sites by passing across atop-Ti metastable positions. For increasing temperatures, however, Cuad transport becomes progressively more isotropic, and switches continuously from normal- to super-diffusive with mean-square displacement dependencies on time that alternate between linear and exponential. Despite that, the Cuad diffusivity D can be expressed by a fairly Arrhenius-like behavior D(T) = 8.26(×2±1) × 10−4 cm2 s−1exp[(−0.04 ± 0.01 eV)/(kBT)] over the entire investigated temperature range (100 ≤ T ≤ 1000 K). AIMD simulations also reveal that the condensation of Cu adatoms into Cux>1 adspecies is kinetically hindered by long-range (>5.5 Å) adatom/adatom repulsion. During Cu island nucleation, all Cu atoms occupy atop-N positions indicating favored Cu(0 0 1)/TiN(0 0 1) epitaxial growth. Nevertheless, Cu agglomerates formed by five, or more, atoms tend to arrange in 3D structures, which maximize intracluster bonds while minimizing film/substrate interactions. Results here presented provide insights for understanding the properties of weakly-interacting metal/substrate interface systems in general.

    The full text will be freely available from 2020-04-22 11:26
  • 53.
    Schmeisser, D.
    et al.
    Schmeißer, D., Angewandte Physik-Sensorik, BTU Cottbus, Erich-Weinert-Str. 1, 03046 Cottbus, Germany.
    Batchelor, D.R.
    Angewandte Physik-Sensorik, BTU Cottbus, Erich-Weinert-Str. 1, 03046 Cottbus, Germany.
    Mikalo, R.P.
    Angewandte Physik-Sensorik, BTU Cottbus, Erich-Weinert-Str. 1, 03046 Cottbus, Germany.
    Hoffmann, P.
    Angewandte Physik-Sensorik, BTU Cottbus, Erich-Weinert-Str. 1, 03046 Cottbus, Germany.
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Oxide growth on SiC(0 0 0 1) surfaces2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 184, no 1-4, p. 340-345Article in journal (Refereed)
    Abstract [en]

    The oxidation of 6H SiC(0 0 0 1) surfaces is studied by high resolution photoelectron spectroscopy. We compare the oxides formed by HF dip, by room temperature treatment in ozone, and by thermal oxidation in air at 1000 °C, respectively. We find a stable intermediate layer in all investigated systems which differs from the bulk oxide that is stable up to 1200 °C. Our data suggest that the growth of the SiO2 layer proceeds via that intermediate silicate layer. © 2001 Published by Elsevier Science B.V.

  • 54.
    Sekora, Derek
    et al.
    University of Nebraska Lincoln, NE USA.
    Briley, Chad
    University of Nebraska Lincoln, NE USA.
    Schubert, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering. University of Nebraska Lincoln, NE USA; Leibniz Institute Polymer Research Dresden, Germany.
    Schubert, Eva
    University of Nebraska Lincoln, NE USA.
    Optical and structural properties of cobalt-permalloy slanted columnar heterostructure thin films2017In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 783-787Article in journal (Refereed)
    Abstract [en]

    Optical and structural properties of sequential Co-column-NiFe-column slanted columnar heterostructure thin films with an A1203 passivation coating are reported. Electron-beam evaporated glancing angle deposition is utilized to deposit the sequential multiple-material slanted columnar heterostructure thin films. Mueller matrix generalized spectroscopic ellipsometry data is analyzed with a best-match model approach employing the anisotropic Bruggeman effective medium approximation formalism to determine bulk-like and anisotropic optical and structural properties of the individual Co and NiFe slanted columnar material sub-layers. Scanning electron microscopy is applied to image the Co-NiFe sequential growth properties and to verify the results of the ellipsometric analysis. Comparisons to single-material slanted columnar thin films and optically bulk solid thin films are presented and discussed. We find that the optical and structural properties of each material sub-layer of the sequential slanted columnar heterostructure film are distinct from each other and resemble those of their respective single-material counterparts. (C) 2016 Elsevier B.V. All rights reserved.

  • 55.
    Semchuk, O. Yu
    et al.
    Institute of Surface Chemistry NAS of Ukraine.
    Semioshko, V.N.
    Institute of Surface Chemistry NAS of Ukraine.
    Grechko, L.G.
    Institute of Surface Chemistry NAS of Ukraine.
    Willander, Magnus
    Goteborg University.
    Karlsteen, M.
    Goteborg University.
    Laser ablation lithography on thermoelectric semconductor2006In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 252, no 13, p. 4759-4762Article in journal (Refereed)
    Abstract [en]

      In this paper, experimental results of the investigation of the periodic structure on thermoelectric semiconductor Cu2Se are presented. Periodic structures were formed on surfaces of semiconductors due to multi-beam interaction of Q-switched Nd:YAG laser, which was operated in the lowest order of Gaussian mode and pulse duration 7 ns. Surface temperature evolution and transient reflectivity are studied during laser treatment. Creation of Cu islands in the maximal intensity of interference pattern was found.

  • 56.
    Shtepliuka, I.
    et al.
    National Academy of Sciences of Ukraine, Kiev.
    Khranovskyy, Volodymyr
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Lashkarev, G.
    National Academy of Sciences of Ukraine, Kiev.
    Khomyak, V.
    Chernivtsi National University, Ukraine.
    Ievtushenko, A.
    National Academy of Sciences of Ukraine, Kiev.
    Tkach, V.
    National Academy of Sciences of Ukraine, Kiev.
    Lazorenko, V.
    National Academy of Sciences of Ukraine, Kiev.
    Timofeeva, I.
    National Academy of Sciences of Ukraine, Kiev.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Microstructure and luminescence dynamics of ZnCdO films with high Cd content deposited on different substrates by DC magnetron sputtering method2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 276, p. 550-557Article in journal (Refereed)
    Abstract [en]

    Investigation of Cd behavior in the ZnCdO alloys, where Cd content exceeds the solubility limit, is of importance due to possible impurity segregation and second phases' formation in this material. We have studied the Cd behavior in the Zn1-xCdxO films deposited by dc magnetron sputtering on different substrates: c-plane Al2O3, bare Si (1 0 0) and Au (45 nm)/Si (1 0 0). It is revealed that Cd content of 10 at. % in the target results in average 6-8 at. % of Cd in the films, depending on the substrate type. Structural analysis based on X-ray diffraction revealed the absence of Cd-related secondary phases. Time-resolved photoluminescence (TRPL) and high-resolution energy dispersive X-ray analysis (EDX) help to understand the recombination dynamics of spontaneous emission and to establish correlations between cadmium content and radiative lifetime. We have revealed that the internal quantum efficiency is influenced by the Cd content and defect concentration. It is suggested that increasing of the cadmium content results in the reduction of nonradiative recombination centers originating from point defects.

  • 57.
    Toropov, A.A.
    et al.
    Ioffe Institute of RAS, Politeknicheskaia 26, 194021, St. Petersburg, Russian Federation.
    Shubina, T.V.
    Ioffe Institute of RAS, Politeknicheskaia 26, 194021, St. Petersburg, Russian Federation.
    Sorokin, S.V.
    Ioffe Institute of RAS, Politeknicheskaia 26, 194021, St. Petersburg, Russian Federation.
    Kyutt, R.N.
    Ioffe Institute of RAS, Politeknicheskaia 26, 194021, St. Petersburg, Russian Federation.
    Ivanov, S.V.
    Ioffe Institute of RAS, Politeknicheskaia 26, 194021, St. Petersburg, Russian Federation.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Karlsteen, M.
    Chalmers Univ. Technol./Goteborg U., S-412 96, Göteborg, Sweden.
    Willander, M.
    Chalmers Univ. Technol./Goteborg U., S-412 96, Göteborg, Sweden.
    Excitons as a probe of interface morphology in Cd(Zn)Se/ZnSe heterostructures2000In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 166, no 1, p. 278-283Article in journal (Refereed)
    Abstract [en]

    We present studies of the excitonic spectrum in superlattices (SLs) of CdSe insertions in a ZnSe matrix aimed at elucidating the CdSe/ZnSe interface morphology. The experimental photoluminescence excitation spectra are compared with the results of variational exciton calculations performed within the effective mass approximation. The shape of the average vertical (along the SL growth axis) distribution of CdSe within each insertion, used in the calculations, was obtained from a theoretical simulation of X-ray diffraction (XRD) rocking curves measured in the same samples. The results indicate that the thinnest layers are graded composition ZnCdSe quantum wells (QWs), generally homogeneous in the layer planes, whereas flat islands enriched by Cd appear at the CdSe nominal thickness larger than 0.5-0.6 monolayer (ML).

  • 58.
    Torrisi, Lorenzo
    et al.
    University of Messina, Italy.
    Cutroneo, Maria
    INFN - Laboratori Nazionali del Sud, Catania, Italy.
    Cavallaro, Salvatore
    INFN - Laboratori Nazionali del Sud, Catania, Italy.
    Giuffirda, Lorenzo
    INFN - Laboratori Nazionali del Sud, Catania, Italy.
    Andò, L.
    INFN - Laboratori Nazionali del Sud, Catania, Italy.
    Cirrone, Pablo
    INFN - Laboratori Nazionali del Sud, Catania, Italy.
    Bertuccio, Giuseppe
    Politecnico di Milano, Como Campus, Italy.
    Puglisi, Donatella
    Politecnico di Milano, Como Campus, Italy.
    Calcagno, Lucia
    University of Catania, Italy.
    Verona, Claudio
    University of Rome "Tor Vergata", Italy.
    Picciotto, A.
    Fondazione Bruno Kessler–IRST, Povo, Trento, Italy.
    Krasa, J.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Margarone, Daniele
    Institute of Physics, ASCR, Prague, Czech Republic.
    Velyhan, A.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Laska, L.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Krousky, E.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Pfeiffer, M.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Skala, J.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Ullschmied, J.
    Institute of Physics, ASCR, Prague, Czech Republic.
    Wolowski, J.
    Institute of Plasma Physics and Laser Microfusion, IPPLM, Waesaw, Poland.
    Badziak, J.
    Institute of Plasma Physics and Laser Microfusion, IPPLM, Waesaw, Poland.
    Rosinski, M.
    Institute of Plasma Physics and Laser Microfusion, IPPLM, Waesaw, Poland.
    Ryc, L.
    Institute of Plasma Physics and Laser Microfusion, IPPLM, Waesaw, Poland.
    Szydlowski, A.
    Institute of Plasma Physics and Laser Microfusion, IPPLM, Waesaw, Poland.
    Proton driven acceleration by intense laser pulses irradiating thin hydrogenated targets2013In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 272, p. 2-5Article in journal (Refereed)
    Abstract [en]

    The Asterix iodine laser of the PALS laboratory in Prague, operating at 1315 nm fundamental frequency, 300 ps pulse duration, 600 J maximum pulse energy and 1016 W/cm2 intensity, is employed to irradiatethin hydrogenated targets placed in high vacuum. Different metallic and polymeric targets allow togenerate multi-energetic and multi-specie ion beams showing peculiar properties. The plasma obtainedby the laser irradiation is monitored, in terms of properties of the emitted charge particles, by using time-of-flight techniques and Thomson parabola spectrometer (TPS). A particular attention is given tothe proton beam production in terms of the maximum energy, emission yield and angular distributionas a function of the laser energy, focal position (FP), target thickness and composition.

  • 59.
    Virojanadara, Chariya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Glans, P.-A.
    Johansson, Leif
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Eickhoff, Th.
    II. Inst. Exp. Phys., Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany.
    Drube, W.
    Hamburger S., Deutschen Elektronen-Synchrt. DESY, D-22603 Hamburg, Germany.
    High energy photoemission investigations of SiO2/SiC samples2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 172, no 3-4, p. 253-259Article in journal (Refereed)
    Abstract [en]

    Chemically etched and directly load-locked SiO2/SiC samples are investigated using a photon energy of 3.0 keV. Si 2p and C 1s spectra recorded at different electron emission angles each show two components originating from SiC, SiO2 and graphite like carbon, respectively. The relative intensity of these are extracted and compared to calculated intensity variations. For the samples investigated, best agreement between experimental and calculated intensity variations is obtained when assuming a graphite like layer on top of the oxide. No graphite like carbon at the SiO2/SiC interface was detected, even on a sample for which the graphite like carbon contribution at the surface corresponds to a layer thickness of only 0.05 angstrom. The energy separation between the oxide and carbide components in the Si 2p spectrum was monitored before and after Ar+ sputtering cycles and before and after in situ heating. The separation increased directly upon sputtering while only in situ heating does not affect it. We suggest that defects induced by the sputtering give rise to the increase, observed in the energy separation.

  • 60.
    Wallin, M.
    et al.
    Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96, Göteborg, Sweden, Dept. of Applied Surface Chemistry, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
    Gronbeck, H.
    Grönbeck, H., Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96, Göteborg, Sweden, Department of Applied Physics, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
    Lloyd-Spets, Anita
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Skoglundh, M.
    Competence Centre for Catalysis, Chalmers University of Technology, SE-412 96, Göteborg, Sweden, Dept. of Applied Surface Chemistry, Chalmers University of Technology, SE-412 96, Göteborg, Sweden.
    Vibrational study of ammonia adsorption on Pt/SiO22004In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 235, no 4, p. 487-500Article in journal (Refereed)
    Abstract [en]

    Vibrational properties of surface species formed upon NH3 adsorption on Pt/SiO2, model system for the gas sensitive part in ammonia sensors based on field effect devices, have been investigated with in situ DRIFT spectroscopy. Experiments have been performed for a series of samples with different Pt loading at three temperatures, 50, 150 and 300°C, and in the absence and presence of oxygen. In addition, electronic structure calculations and vibrational analysis have been performed within the density functional theory (DFT) for NH3 and NH2 species adsorbed on platinum and hydroxylated silica model systems. Observations from both DRIFT spectra and DFT calculations indicate that NH3 is more strongly bound to platinum than to silanol groups on the SiO2 support. Vibrational modes assigned to NH2 appeared in the DRIFT experiments, indicative of NH3 dissociation, an interpretation supported by the calculations. Exposure of O2 was found to have minor effect on the vibrational spectrum at 50°C. However, at 150°C an increase of the vibration band assigned to the NH2 surface species was observed together with formation of gas phase N2O for samples with high platinum content. Thus, ammonia is oxidised over Pt at this temperature and oxygen is most likely facilitating ammonia dissociation. © 2004 Elsevier B.V. All rights reserved.

  • 61.
    Wongmanerod, C.
    et al.
    Department of Physics, Fac. Sci., Chulalongkorn U., Bangkok, Thailand.
    Zangooie, S.
    Department of Electrical Engineering, Ctr. Microlectron. Optical Mat. R., Lincoln, NE 68588-0511, United States.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Determination of pore size distribution and surface area of thin porous silicon layers by spectroscopic ellipsometry2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 172, no 1-2, p. 117-125Article in journal (Refereed)
    Abstract [en]

    A non-destructive method for investigation of pore size distribution and surface area of porous silicon is presented. Adsorption and desorption isotherms of water in thin films of porous silicon are analyzed using variable angle of incidence spectroscopic ellipsometry. The analysis is based on multilayer optical models and the Bruggeman effective medium approximation. Pore size distribution and surface area are extracted from the isotherms employing the Wheeler theory combined with the Kelvin and Cohan equations. Good agreement is obtained between the calculated pore size distribution and estimations made by scanning electron microscopy. The evaluated specific surface area for the porous layers presented here is approximately 180 m2/cm3, which is in good agreement with the value reported in the literature.

  • 62.
    Wronkowska, A.A.
    et al.
    Instytut Matematyki i Fizyki, Akademia Techniczno-Rolnicza, Al. S. Kaliskiego 7, Bydgoszcz PL-85 796, Poland.
    Wronkowski, A.
    Instytut Matematyki i Fizyki, Akademia Techniczno-Rolnicza, Al. S. Kaliskiego 7, Bydgoszcz PL-85 796, Poland.
    Bukaluk, A.
    Instytut Matematyki i Fizyki, Akademia Techniczno-Rolnicza, Al. S. Kaliskiego 7, Bydgoszcz PL-85 796, Poland.
    Stefanski, M.
    Stefanski, M., Instytut Matematyki i Fizyki, Akademia Techniczno-Rolnicza, Al. S. Kaliskiego 7, Bydgoszcz PL-85 796, Poland.
    Arwin, Hans
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Optics .
    Firszt, F.
    Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. Grudzia¸dzka 5, Torun PL-87 100, Poland.
    Legowski, S.
    L?gowski, S., Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. Grudzia¸dzka 5, Torun PL-87 100, Poland.
    Meczynska, H.
    M?czynska, H., Instytut Fizyki, Uniw. Mikolaja Kopernika, Ul. Grudzia¸dzka 5, Torun PL-87 100, Poland.
    Hradil, K.
    Universität Würzburg, Mineralogisches Institut, Am Hubland, Würzburg, Germany.
    Investigations of Cd1-xMnxTe crystals by means of ellipsometry and Auger electron spectroscopy2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 212-213, no SPEC., p. 110-115Conference paper (Other academic)
    Abstract [en]

    Cd1-xMnxTe crystals, obtained by the high-pressure Bridgman method for x = 0, 0.27, 0.49, 0.67 and 0.8, were investigated. Crystal composition was determined by electron microprobe analysis. For an Mn content lower than 0.7, a single phase of pure zinc blend structure was found. In Cd0.2Mn0.8Te samples a two-phase structure was revealed. Auger electron spectroscopy (AES) was used to determine the composition of the crystal surfaces. AES depth profiles obtained by argon sputtering and AES analysis allowed to find the distribution of Cd, Mn and Te inside the sub-surface region. Spectroscopic ellipsometry was applied to determine the complex dielectric function e of the samples. Ellipsometric measurements were performed at room temperature in the photon energy range 0.75-6.5 eV. The spectral dependence of e was used to find the energy gaps Eg of the alloys with different Mn content. Ellipsometric data were correlated with the compositional results obtained from the electron microprobe and AES depth profile investigations. A linear increase of energy gaps with increasing x was observed for chemically homogeneous CdMnTe crystals. © 2003 Elsevier Science B.V. All rights reserved.

  • 63.
    Yang, Li-Li
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology. Institute of Condensed State Physics, Jilin Normal University, Siping, People's Republic of China.
    Zhao, Qingxiang
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Yang, J H
    Institute of Condensed State Physics, Jilin Normal University, Siping, People's Republic of China.
    Origin of the surface recombination centers in ZnO nanorods arrays by X-ray photoelectron spectroscopy2010In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 256, no 11, p. 3592-3597Article in journal (Refereed)
    Abstract [en]

    The surface composition of as-grown and annealed ZnO nanorods arrays (ZNAs) grown by a two-step chemical bath deposition method has been investigated by X-ray photoelectron spectroscopy (XPS). XPS confirms the presence of OH bonds and specific chemisorbed oxygen on the surface of ZNAs, as well as H bonds on (1 0 (1) over bar 0) surfaces which has been first time observed in the XPS spectra. The experimental results indicated that the OH and H bonds play the dominant role in facilitating surface recombination but specific chemisorbed oxygen also likely affect the surface recombination. Annealing can largely remove the OH and H bonds and transform the composition of the other chemisorbed oxygen at the surface to more closely resemble that of high temperature grown ZNAs, all of which suppresses surface recombination according to time-resolved photoluminescence measurements.

  • 64.
    Yang, L.L.
    et al.
    Jilin Normal University.
    Zhao, Qingxiang
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Xing, G.Z.
    Nanyang Technology University.
    Wang, D.D.
    Nanyang Technology University.
    Wu, T.
    Nanyang Technology University.
    Willander, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gueorguiev Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yang, J.H.
    Jilin Normal University.
    A SIMS study on Mg diffusion in Zn(0.94)Mg(0.06)O/ZnO heterostructures grown by metal organic chemical vapor deposition2011In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 257, no 20, p. 8629-8633Article in journal (Refereed)
    Abstract [en]

    Zn(0.94)Mg(0.06)O/ZnO heterostructures have been grown on 2 in. sapphire wafer using metal organic chemical vapor deposition (MOCVD). Photoluminescence (PL) mapping demonstrates that Mg distribution on the entire wafer is very uniform (standard deviation of Mg concentration/mean Mg concentration = 1.38%) with average concentration of similar to 6%. The effect of annealing on the Mg diffusion in Zn(0.94)Mg(0.06)O/ZnO heterostructures has been investigated in detail by using secondary ion mass spectrometry (SIMS). All the Mg SIMS depth profiles have been fitted by three Gaussian distribution functions. The Mg diffusion coefficient in the as-grown Zn(0.94)Mg(0.06)O layer deposited at 700 degrees C is two orders of magnitude lower than that of annealed samples, which clearly indicates that the deposition temperature of 700 degrees C is much more beneficial to grow ZnMgO/ZnO heterostructures and quantum wells.

  • 65.
    Yazdi, Gholamreza
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Akhtar, Fatima
    IHP, Germany.
    Ivanov, Ivan Gueorguiev
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Schmidt, Susann
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Shtepliuk, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Zakharov, Alexei
    Lund Univ, Sweden.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Effect of epitaxial graphene morphology on adsorption of ambient species2019In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 486, p. 239-248Article in journal (Refereed)
    Abstract [en]

    This work illustrates the impact of atmospheric gases on the surface of epitaxial graphene. The different rate of adsorption on different parts of graphene samples provides a concrete evidence that the surface morphology of graphene plays a significant role in this process. The uneven adsorption occurs only on the surface of the monolayer graphene and not on bilayer graphene. The second monolayer is distinguished and verified by the phase contrast mode of atomic force microscopy and the low energy electron microscopy, respectively. Raman spectroscopy is used to study the strain on the surface of graphene; results indicate that monolayer and bilayer graphene exhibit different types of strain. The bilayer is under more compressive strain in comparison with monolayer graphene that hinders the process of adsorption. However, the wrinkles and edges of steps of the bilayer are under tensile strain, hence, facilitate adsorption. Samples were subjected to X-ray photoelectron spectroscopy which confirms that the adsorbates on the epitaxial graphene are carbon clusters with nitrogen and oxygen contamination. For reversing the adsorption process the samples are annealed and a method for the removal of these adsorbates is proposed.

  • 66.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Balasubramanian, T
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Univ Lund, Max Lab, S-22100 Lund, Sweden.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics .
    Surface electronic structure of the root 3x root 3, root 39x root 39 and 6x6 surfaces of Ag/Ge(111): observation of a metal to semiconductor transition2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 175, p. 237-242Article in journal (Refereed)
    Abstract [en]

    Deposition of 1 monolayer (ML) of Ag on the clean Ge(1 1 1) surface, followed by annealing at 300 degreesC for 2 min, results in a sharp root3 x root3 low-energy electron diffraction (LEED) pattern. This surface transforms into a root 39 x root 39 surface, as observed by LEED, due to a tiny amount of additional Ag atoms when the temperature is below approximately -20 degreesC. The presence of the additional Ag leads to an increased filling of two partially occupied surface bands. By depositing approximately 0.2 ML of Ag on the root3 x root3 surface, it transforms into a 6 x 6 periodicity. The addition of Ag leads to an interesting transition from the metallic surfaces (root3 x root3 and root 39 x root 39) to the semiconducting 6 x 6 surface with a gap of around 0.2 eV with respect to the Fermi-level. On the 6 x 6 phase, the lower one of the partially occupied surface bands of the root3 x root3 and root 39 x root 39 surfaces seems to be entirely pulled down below the Fermi-level, while the upper one is missing. The electronic structures of the different Ag/Ge(111) surfaces an also discussed in comparison with the Ag/Si(111) surfaces. (C) 2001 Elsevier Science B.V. All rights reserved.

  • 67.
    Zhang, Hanmin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Sakamoto, K
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Uhrberg, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics. Linköping University, The Institute of Technology.
    Semiconductor-metal-semiconductor transition: valence band photoemission study of Ag/Si(111) surfaces2002In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 190, no 1-4, p. 103-107Article in journal (Refereed)
    Abstract [en]

    The root3 x root3, root21 x root21 and 6 x 6 phases of Ag/Si(111) have been studied by angle-resolved photoemission and low-energy electron diffraction. The Ag/Si(111) root3 x root3 surface has an intrinsic semiconducting character with two fully occupied, dispersing surface state bands. We find that only one of the additional surface bands on the root21 x root21 surface is metallic in contrast to the two metallic bands discussed in the literature. On the 6 x 6 surface, the partially occupied surface band of the root21 x root21 surface seems to be absent, resulting in a gap of about 0.2 eV with respect to the Fermi-level. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 68.
    Zhang, Hanmin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Uhrberg, Roger
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface and Semiconductor Physics.
    Atomic structures of Ag/Ge(1 1 1) v39 × v39 and 6 × 6 surfaces studied by STM: Observations of bias dependent reconstruction transformations2003In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 212-213, no SPEC., p. 353-359Article in journal (Refereed)
    Abstract [en]

    The 6 × 6 and v39 × v39 phases on Ag/Ge(1 1 1) have been studied by scanning tunneling microscopy (STM). Four types of 6 × 6 configurations are found which all consist of a v3 × v3 layer with six extra Ag adatoms per 6 × 6 unit cell. These reconstructions show either mirrored or complementary relations. We observe interesting transitions between the different 6 × 6 reconstructions. The v39 × v39 surface appears to have five extra Ag atoms per unit cell. By using various tip biases, we show that the v39 × v39 domain orientation can be changed. Surface structure models of the v39 × v39 and 6 × 6 phases are proposed based on the HCT structure of the underlying v3 × v3 surface. © 2003 Elsevier Science B.V. All rights reserved.

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