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  • 201.
    Echresh, Ahmad
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology. Shahid Chamran University of Ahvaz, Iran.
    Oeurn Chey, Chan
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Zargar Shoushtari, Morteza
    Shahid Chamran University of Ahvaz, Iran.
    Nur, Omer
    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.
    Tuning the emission of ZnO nanorods based light emitting diodes using Ag doping2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 19, p. 2-9Article in journal (Refereed)
    Abstract [en]

    We have fabricated, characterized, and compared ZnO nanorods/p-GaN and n-Zn0.94Ag0.06O nanorods/p-GaN light emitting diodes (LEDs). Current-voltage measurement showed an obvious rectifying behaviour of both LEDs. A reduction of the optical band gap of the Zn0.94Ag0.06O nanorods compared to pure ZnO nanorods was observed. This reduction leads to decrease the valence band offset at n-Zn0.94Ag0.06O nanorods/p-GaN interface compared to n-ZnO nanorods/p-GaN heterojunction. Consequently, this reduction leads to increase the hole injection from the GaN to the ZnO. From electroluminescence measurement, white light was observed for the n-Zn0.94Ag0.06O nanorods/p-GaN heterojunction LEDs under forward bias, while for the reverse bias, blue light was observed. While for the n-ZnO nanorods/p-GaN blue light dominated the emission in both forward and reverse biases. Further, the LEDs exhibited a high sensitivity in responding to UV illumination. The results presented here indicate that doping ZnO nanorods might pave the way to tune the light emission from n-ZnO/p-GaN LEDs.

  • 202.
    Edström, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Sangiovanni, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Ruhr University of Bochum, Germany.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA.
    Chirita, Valeriu
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Effects of incident N atom kinetic energy on TiN/TiN(001) film growth dynamics: A molecular dynamics investigation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 2, article id 025302Article in journal (Refereed)
    Abstract [en]

    Large-scale classical molecular dynamics simulations of epitaxial TiN/TiN(001) thin film growth at 1200 K, a temperature within the optimal range for epitaxial TiN growth, with an incident N-to-Ti flux ratio of four, are carried out using incident N energies E-N = 2 and 10 eV and incident Ti energy E-Ti = 2 eV. To further highlight the effect of E-N, we grow a bilayer film with E-N = 2 eV initially and then switch to E-N = 10 eV. As-deposited layers are analyzed as a function of composition, island-size distribution, island-edge orientation, and vacancy formation. Results show that growth with E-N = 2 eV results in films that are globally overstoichiometric with islands bounded by N-terminated polar 110 edges, whereas films grown with E-N = 10 eV are flatter and closer to stoichiometric. However, E-N = 10 eV layers exhibit local N deficiency leading to the formation of isolated 111-oriented islands. Films grown by changing the incident energy from 2 to 10 eV during growth are more compact than those grown entirely with E-N = 2 eV and exhibit greatly reduced concentrations of upper-layer adatoms, admolecules, and small clusters. Islands with 110 edges formed during growth with E-N = 2 eV transform to islands with 100 edges as E-N is switched to 10 eV. Published by AIP Publishing.

  • 203.
    Efthimiopoulos, I.
    et al.
    Natl Hellen Res Fdn, Greece;Deutsch GeoForschungsZentrum GFZ, Germany.
    Palles, D.
    Natl Hellen Res Fdn, Greece.
    Richter, S.
    Friedrich Schiller Univ Jena, Germany;TRUMPF Lasertech GmbH, Germany.
    Hoppe, U.
    Univ Rostock, Germany.
    Möncke, Doris
    Linnaeus University, Faculty of Technology, Department of Built Environment and Energy Technology. Natl Hellen Res Fdn, Greece.
    Wondraczek, L.
    Friedrich Schiller Univ Jena, Germany;Fraunhofer Inst Appl Opt & Precis Engn, Germany.
    Nolte, S.
    Friedrich Schiller Univ Jena, Germany;Fraunhofer Inst Appl Opt & Precis Engn, Germany.
    Kamitsos, E. I.
    Natl Hellen Res Fdn, Greece.
    Femtosecond laser-induced transformations in ultra-low expansion glass: Microstructure and local density variations by vibrational spectroscopy2018In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 23, article id 233105Article in journal (Refereed)
    Abstract [en]

    We report X-ray diffraction, resonance Raman, and infrared (IR) results on pristine ultra-low expansion (ULE) glass, a binary titanosilicate glass with 5.67 mol. % TiO2. ULE processing by femtosecond (fs) laser radiation leads to nanograting writing and photo-darkening for imaging and data storage. We investigate here the vibrational/structural changes induced by fs laser irradiation of ULE at 515 nm. Optical imaging revealed the formation of micro-cavities, and Raman mapping showed molecular oxygen trapped in such cavities of laser-irradiated ULE glass. While titanium in the pristine glass was found predominantly in tetrahedral Ti4+ sites highly dispersed in the silicate matrix, Raman and IR reflectance spectroscopy on laser-irradiated ULE indicated the formation of Ti3+ sites; Ti3+ octahedral sites are formed in the shells of cavities and aggregate in amorphous Ti2O3-type clusters, while the glass around and below cavities contains Ti3+ tetrahedral sites dispersed in the silicate network. Laser-processed ULE glass was found to also exhibit local restructuring of the silicate matrix. Shifts of the strong IR band at about 1080-1100 cm(-1) were translated into changes of the average Si-O-Si bond angle in the laser-transformed areas and found to reflect local density variations; the average local density increases relative to silica glass up to about 8% in the shells of micro-cavities and decreases by about 0.5% in the surrounding material. Chemical processes were proposed to account for photo-darkening and the local structural transformation effect in the probed areas of the fs laser-processed ULE glasses. Published by AIP Publishing.

  • 204. Egilsson, T.
    et al.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Henry, Anne
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Janzén, Erik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Excitation spectra of nitrogen bound excitons in 4H- and 6H-SiC2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 3, p. 2028-2032Article in journal (Refereed)
    Abstract [en]

    We report photoluminescence excitation spectra of the nitrogen (N) donor bound excitons (BE) in 4H- and 6H-SiC. The spectra reveal several excited states of the N-BEs. An attempt is made in the article to classify the N-BE states according to a simple shell model. © 2002 American Institute of Physics.

  • 205. Ekvall, K.
    et al.
    van der Meulen, P.
    Dhollande, C.
    Berg, Lars-Erik
    KTH, Superseded Departments, Physics.
    Pommeret, S.
    Naskrecki, R.
    Mialocq, J. C.
    Cross phase modulation artifact in liquid phase transient absorption spectroscopy2000In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 87, no 5, p. 2340-2352Article in journal (Refereed)
    Abstract [en]

    We present experimental results for the cross phase modulation (xpm) induced transient absorption signal in a 1 mm thick fused silica plate using a white light continuum as a probe. The fused silica plate mimics the entrance window of a commercial flow cell commonly used in liquid-phase transient absorption measurements. The experimental results are compared with those obtained theoretically by numerically solving the set of nonlinear coupled wave equations describing the propagation of the pump and the probe. The simulations allow for the different group velocities of the pump and probe pulses, and include the influence of the first and second order dispersion on the continuum probe. From the calculations the physical origin of the complex oscillatory feature observed around the zero time delay of each wavelength of the (chirped) continuum has been accurately identified. The influence of propagation effects arising from the finite thickness of the sample is discussed in great detail, and the necessity to work with thin samples, preferably free-flowing jets, is emphasized. The good agreement between theory and experiment indicates that the xpm artifact may be useful for characterizing the continuum probe, in particular its chirp.

  • 206. Elihn, K
    et al.
    Landström, Lars
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry.
    Alm, Oscar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Boman, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Heszler, Peter
    Size and structure of nanoparticles formed via ultraviolet photolysis of ferrocene2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 3, p. 034311-Article in journal (Refereed)
    Abstract [en]

    Iron nanoparticles enclosed in carbon shells were formed by laser-assisted chemical vapor decomposition of ferrocene (Fe(C5H5)2) vapor in Ar gas atmosphere. The particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser was examined and, e.g., an effective size decrease of the iron core was observed at elevated laser fluences. Characterizations of the iron and carbon microstructures were performed by x-ray diffraction and transmission electron microscopy, while relative iron deposition rates were measured by x-ray fluorescence spectroscopy. Both -Fe and -Fe phases were found for the single crystalline iron cores, surrounded by graphitic (inner) and amorphous (outer) carbon layers. The temperature rise of the laser-excited particles was also determined by optical spectroscopy of the emitted thermal radiation, which allowed an estimation of the iron loss of the nanoparticles due to evaporation. The estimated and measured iron losses are in good agreement.

  • 207.
    Elihn, Karine
    et al.
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Landstroem, L.
    Alm, O.
    Boman, M.
    Heszler, P.
    Size and structure of nanoparticles formed via ultraviolet photolysis of ferrocene2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 3, p. 34311-Article in journal (Refereed)
    Abstract [en]

    Iron nanoparticles enclosed in carbon shells were formed by laser-assisted chemical vapor decomposition of ferrocene (Fe(C5H5)(2)) vapor in Ar gas atmosphere. The particle size dependence on the total ambient gas pressure and on laser fluence of the pulsed ArF excimer laser was examined and, e.g., an effective size decrease of the iron core was observed at elevated laser fluences. Characterizations of the iron and carbon microstructures were performed by x-ray diffraction and transmission electron microscopy, while relative iron deposition rates were measured by x-ray fluorescence spectroscopy. Both alpha-Fe and gamma-Fe phases were found for the single crystalline iron cores, surrounded by graphitic (inner) and amorphous (outer) carbon layers. The temperature rise of the laser-excited particles was also determined by optical spectroscopy of the emitted thermal radiation, which allowed an estimation of the iron loss of the nanoparticles due to evaporation. The estimated and measured iron losses are in good agreement. 

  • 208.
    Elofsson, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Almyras, Georgios
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Lü, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Garbrecht, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Boyd, Robert
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Nanoscale engineering. Linköping University, Faculty of Science & Engineering.
    Structure formation in Ag-X (X = Au, Cu) alloys synthesized far-from-equilibrium2018In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 123, no 16Article in journal (Refereed)
    Abstract [en]

    We employ sub-monolayer, pulsed Ag and Au vapor fluxes, along with deterministic growth simulations, and nanoscale probes to study structure formation in miscible Ag-Au films synthesized under far-from-equilibrium conditions. Our results show that nanoscale atomic arrangement is primarily determined by roughness build up at the film growth front, whereby larger roughness leads to increased intermixing between Ag and Au. These findings suggest a different structure formation pathway as compared to the immiscible Ag-Cu system for which the present study, in combination with previously published data, reveals that no significant roughness is developed, and the local atomic structure is predominantly determined by the tendency of Ag and Cu to phase-separate.

  • 209.
    Elofsson, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Magnfält, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Unravelling the Physical Mechanisms that Determine Microstructural Evolution of Ultrathin Volmer-Weber Films2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 4, p. 044302-Article in journal (Refereed)
    Abstract [en]

    The initial formation stages (i.e., island nucleation, island growth, and island coalescence) set characteristic length scales during growth of thin films from the vapour phase. They are, thus, decisive for morphological and microstructural features of films and nanostructures. Each of the initial formation stages has previously been well-investigated separately for the case of Volmer-Weber growth, but knowledge on how and to what extent each stage individually and all together affect the microstructural evolution is still lacking. Here we address this question using growth of Ag on SiO2 from pulsed vapour fluxes as a case study. By combining in situ growth monitoring, ex situ imaging and growth simulations we systematically study the growth evolution all the way from nucleation to formation of a continuous film and establish the effect of the vapour flux time domain on the scaling behaviour of characteristic growth transitions (elongation transition, percolation and continuous film formation). Our data reveal a pulsing frequency dependence for the characteristic film growth transitions, where the nominal transition thickness decreases with increasing pulsing frequency up to a certain value after which a steady-state behaviour is observed. The scaling behaviour is shown to result from differences in island sizes and densities, as dictated by the initial film formation stages. These differences are determined solely by the interplay between the characteristics of the vapour flux and time required for island coalescence to be completed. In particular, our data provide evidence that the steady-state scaling regime of the characteristic growth transitions is caused by island growth that hinders coalescence from being completed, leading to a coalescence-free growth regime.

  • 210.
    Elofsson, Viktor
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Magnfält, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Samuelsson, M
    Impact Coatings, Linköping, Sweden .
    Sarakinos, Kostas
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, The Institute of Technology.
    Tilt of the columnar microstructure in off-normally deposited thin films using highly ionized vapor fluxes2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 17, p. 7 pages-Article in journal (Refereed)
    Abstract [en]

    The tilt of the columnar microstructure has been studied for Cu and Cr thin films grown off-normally using highly ionized vapor fluxes, generated by the deposition technique high power impulse magnetron sputtering. It is found that the relatively large column tilt (with respect to the substrate normal) observed for Cu films decreases as the ionization degree of the deposition flux increases. On the contrary, Cr columns are found to grow relatively close to the substrate normal and the column tilt is independent from the ionization degree of the vapor flux when films are deposited at room temperature. The Cr column tilt is only found to be influenced by the ionized fluxes when films are grown at elevated temperatures, suggesting that film morphology during the film nucleation stage is also important in affecting column tilt. A phenomenological model that accounts for the effect of atomic shadowing at different nucleation conditions is suggested to explain the results.

  • 211.
    Emmerlich, Jens
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Högberg, Hans
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sasvári, Szilvia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Palmquist, Jens-Petter
    Department of Material Chemistry, Uppsala University, The Ångström Laboratory, Uppsala, Sweden .
    Jansson, Ulf
    Department of Material Chemistry, Uppsala University, The Ångström Laboratory, Uppsala, Sweden .
    Molina-Aldareguia, Jon M.
    CEIT (Centro de Estudios e Investigaciones Técnicas e Gipuzkoa), Spain .
    Czigány, Zsolt
    Research Institute for Technical Physics and Materials Science, Hungary .
    Growth of Ti3SiC2 thin films by elemental target magnetron sputtering2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 9, p. 4817-4826Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2(0001) thin films have been deposited by dc magnetron sputtering from three elemental targets of Ti, C, and Si onto MgO(111) and Al2O3(0001) substrates at temperatures of 800–900 °C. This process allows composition control to synthesize Mn+1AXn (MAX) phases (M: early transition metal; A: A-group element; X: C and∕or N; n=1–3) including Ti4SiC3. Depositions on MgO(100) substrates yielding the Ti–Si–C MAX phases with (105), as the preferred orientation. Samples grown at different substrate temperatures, studied by means of transmission electron microscopy and x-ray diffraction investigations, revealed the constraints of Ti3SiC2 nucleation due to kinetic limitations at substrate temperatures below 700 °C. Instead, there is a competitive TiCx growth with Si segregation to form twin boundaries or Si substitutional incorporation in TiCx. Physical properties of the as-deposited single-crystal Ti3SiC2 films were determined. A low resistivity of 25 μΩ cm was measured. The Young’s modulus, ascertained by nanoindentation, yielded a value of 343–370 GPa. For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost 30 GPa. With increased maximum indentation loads, the hardness was observed to decrease toward bulk values as the characteristic kink formation sets in with dislocation ordering and delamination at basal planes.

  • 212. Emmerlich, Jens
    et al.
    Högberg, Hans
    Sasvári, Szilvia
    Persson, Per O. Å
    Hultman, Lars
    Palmquist, Jens-Petter
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Jansson, Ulf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry.
    Molina-Aldareguia, Jon M
    Czigány, Zsolt
    Growth of Ti3SiC2 thin films by elemental target magnetron sputtering2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 9, p. 4817-4826Article in journal (Refereed)
    Abstract [en]

    Epitaxial Ti3SiC2(0001) thin films have been deposited by dc magnetron sputtering from three elemental targets of Ti, C, and Si onto MgO(111) and Al2O3(0001) substrates at temperatures of 800–900 °C. This process allows composition control to synthesize Mn + 1AXn (MAX) phases (M: early transition metal; A: A-group element; X: C and/or N; n = 1–3) including Ti4SiC3. Depositions on MgO(100) substrates yielding the Ti–Si–C MAX phases with (105), as the preferred orientation. Samples grown at different substrate temperatures, studied by means of transmission electron microscopy and x-ray diffraction investigations, revealed the constraints of Ti3SiC2 nucleation due to kinetic limitations at substrate temperatures below 700 °C. Instead, there is a competitive TiCx growth with Si segregation to form twin boundaries or Si substitutional incorporation in TiCx. Physical properties of the as-deposited single-crystal Ti3SiC2 films were determined. A low resistivity of 25 µ cm was measured. The Young's modulus, ascertained by nanoindentation, yielded a value of 343–370 GPa. For the mechanical deformation response of the material, probing with cube corner and Berkovich indenters showed an initial high hardness of almost 30 GPa. With increased maximum indentation loads, the hardness was observed to decrease toward bulk values as the characteristic kink formation sets in with dislocation ordering and delamination at basal planes.

  • 213.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bergqvist, A.
    Lundgren, A.
    Stillesjö, F.
    Statistical modeling of magnetic and magnetostrictive properties due to domain wall motion1999In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, ISSN 0021-8979, Vol. 85, no 8, p. 5190-5192Article in journal (Refereed)
    Abstract [en]

    Statistical mechanics is employed to derive magnetic and magnetostrictive bulk properties of soft magnetic materials dominated by domain wall motion. The material is divided into an ensemble of volumes with uniform magnetization, each one much smaller than a typical domain but much larger than one atom. The energy for such a volume element is assumed to consist of an internal energy: the interaction with the external magnetic field and a mean field interaction with the surrounding medium. The volume fractions of discrete mesoscopic magnetizations in the medium are derived from Boltzmann statistics. The bulk magnetization is the weighted average of the mesoscopic values. Magnetostriction is treated in a similar way. Calculations are compared with two-dimensional measurements on grain-oriented silicon #x2013;iron. #xa9; 1999 American Institute of Physics.

  • 214.
    Engdahl, Göran
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Svensson, L.
    Simulation of the magnetostrictive performance of Terfenol-D in mechanical devices1988In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 63, p. 3924-3926Article in journal (Refereed)
    Abstract [en]

    A dynamic simulation model has been developed. Registered data from static measurements of the magnetostrictive strain for different magnetizations and mechanical stresses are used as numerical input. Easy examination of differences in dynamic performance between samples of different compositions and manufacturing methods is also possible due to a computer #x2010;aided input data handling system. The shape of the imposed magnetization can be a step, impulse, sinusoidal, or an arbitrary function. The mechanical load can be a prescribed force against the magnetostrictive element or an arbitrarily chosen mechanical impedance. The model has been verified against dynamic measurements in an experimental setup for sinusoidal and impulse magnetizations. Comparison between the model and the experimental data reveals that the model is a powerful tool for designing magnetomechanical devices based on giant magnetostrictive materials.

  • 215.
    Engström, Jens
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Mikael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Göteman, Malin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Performance of large arrays of point absorbing direct-driven wave energy converters2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 20, p. 204502-Article in journal (Refereed)
    Abstract [en]

    Future commercial installation of wave energy plants using point absorber technology will require clusters of tens up to several hundred devices, in order to reach a viable electricity production. Interconnected devices also serve the purpose of power smoothing, which is especially important for devices using direct-driven power take off. The scope of this paper is to evaluate a method to optimize wave energy farms in terms of power production, economic viability and resources. In particular, the paper deals with the power variation in a large array of point-absorbing direct-driven wave energy converters, and the smoothing effect due to the number of devices and their hydrodynamic interactions. A few array geometries are compared and 34 sea states measured at the Lysekil research site at the Swedish west coast are used in the simulations. Potential linear flow theory are used with full hydrodynamic interactions between the buoys. It is shown that the variance in power production depends crucially on the geometry of the array and the number of interacting devices, but not significantly on the energy period of the waves.

  • 216.
    Engström, Jens
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Eriksson, Mikael
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wave energy converter with enhanced amplitude response at frequencies coinciding with Swedish west coast sea states by use of a supplementary submerged body2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 6, article id 064512Article in journal (Refereed)
    Abstract [en]

    The full-scale direct-driven wave energy converter developed at Uppsala University has been in offshore operation at the Swedish west coast since 2006. Earlier simulations have now been validated by full-scale experiment with good agreement. Based on that, a theoretical model for a passive system having optimum amplitude response at frequencies coinciding with Swedish west coast conditions has been developed. The amplitude response is increased by adding supplementary inertia by use of the additional mass from a submerged body. A sphere with neutral buoyancy is chosen as the submerged body and modeled as being below the motion of the waves. The model is based on potential linear wave theory and the power capture ratio is studied for real ocean wave data collected at the research test site. It is found that the power capture ratio for the two body system can be increased from 30% to 60% compared to a single body system. Increased velocity in the system also decreases the value for optimal load damping from the generator, opening up the possibility to design smaller units.

  • 217.
    Engström, Jens
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Kurupath, Venugopalan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    A resonant Two Body System for a point absorbing Wave Energy Converter with direct-driven linear generator2011In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 110, no 12, p. 124904-Article in journal (Refereed)
    Abstract [en]

    Based on an earlier conceptual model of a two body system point absorbing wave energy converter tuned to resonance in Swedish west coast sea states, an extended coupled hydrodynamic, mechanic, and electromagnetic model has been developed. The hydrodynamic characteristics of the two body system are studied in the frequency and time domain, while its response to real Swedish west coast sea states are studied in the time domain, by using a wave energy converter model with two independently moving bodies connected to a direct driven linear generator with non-linear damping. The two body system wave energy converter gives nearly 80% power capture ratio in irregular waves. The resonant behaviour is shown to be sensitive to the shape of the spectrum, and the distance between the two bodies is shown to have a large effect on the power absorption.

  • 218.
    Eriksson, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Zhirkov, I.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Dahlqvist, Martin
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Jensen, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Rosen, J.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Characterization of plasma chemistry and ion energy in cathodic arc plasma from Ti-Si cathodes of different compositions2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 16Article in journal (Refereed)
    Abstract [en]

    Arc plasma from Ti-Si compound cathodes with up to 25 at. % Si was characterized in a DC arc system with respect to chemistry and charge-state-resolved ion energy. The plasma ion composition showed a lower Si content, diverging up to 12 at. % compared to the cathode composition, yet concurrently deposited films were in accordance with the cathode stoichiometry. Significant contribution to film growth from neutrals is inferred besides ions, since the contribution from macroparticles, estimated by scanning electron microscopy, cannot alone account for the compositional difference between cathode, plasma, and film. The average ion charge states for Ti and Si were higher than reference data for elemental cathodes. This result is likely related to TiSix phases of higher cohesive energies in the compound cathodes and higher effective electron temperature in plasma formation. The ion energy distributions extended up to ∼200 and ∼130 eV for Ti and Si, respectively, with corresponding average energies of ∼60 and ∼30 eV. These averages were, however, not dependent on Si content in the cathode, except for 25 at. % Si where the average energies were increased up to 72 eV for Ti and 47 eV for Si.

  • 219.
    Eriksson, Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Reflectivity and structural evolution of Cr/Sc and nitrogen containing Cr/Sc multilayers during thermal annealing2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 104, no 6, p. 063516-Article in journal (Refereed)
    Abstract [en]

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

  • 220.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Hydrogen adsorption states at the Pd-SiO2 interface and simulation of the response of a Pd metal-oxide-semiconductor hydrogen sensor1998In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 83, no 8, p. 3947-3951Article in journal (Refereed)
    Abstract [en]

    The response of a Pd–SiO 2 –Si hydrogen sensor depends on the reaction kinetics of hydrogen on the Pd surface and on the hydrogen adsorption states at the Pd/SiO 2 interface. In this work we show that besides the dominating hydrogen adsorption state located on the oxide side of the interface, a second state, resulting in opposite hydrogen polarization, exists. This state is possibly a reminiscence of the hydrogen adsorption state on a clean Pd surface. Taking both states into account, a simulation of the hydrogen response over more than ten decades in hydrogen pressures gives good agreement with published data.

  • 221.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Chemical and Optical Sensor Systems. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, Faculty of Science & Engineering.
    Ekedahl, Lars-Gunnar
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    A model of the Temkin isotherm behaviour for hydrogen adsorption at Pd-SiO2 interfaces1997In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 82, no 6, p. 3143-3146Article in journal (Refereed)
    Abstract [en]

    A simple electrostatic model of the adsorbate–adsorbateinteraction of hydrogen atoms at a Pd–SiO 2 interface is presented. The model predicts a hydrogen adsorption isotherm of the Temkin type. It is found that, in practice, an upper limit for the hydrogen response of a Pd-metal-oxide-semiconductor device exists. The value (in V) is equal to the difference of the initial heats of adsorption (in eV) of the interface and the Pd bulk, respectively. Furthermore, a corresponding maximum hydrogen concentration, at the interface, of 1×10 18  m −2 is predicted. The predictions are in good agreement with previously observed experimental data.

  • 222.
    Eriksson, Mats
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Salomonsson, Anette
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Briand, Danick
    Institute of Microtechnology, University of Neuchâtel, Neuchâtel, Switzerland.
    Åbom, Elisabeth
    Sapa Heat Transfer, Finspång, Sweden.
    The influence of the insulator surface properties on the hydrogen response of field-effect gas sensors2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 98, no 3, p. 34903-34908Article in journal (Refereed)
    Abstract [en]

    The hydrogen response of gas-sensitive field-effect devices is mainly due to trapping of atomic hydrogen on the insulator side of the metal-insulator interface of the metal-insulator-semiconductor (MIS) structure. Therefore an influence of the choice of insulator on the hydrogen response properties is expected. We have investigated this influence by producing MIS capacitors with four different insulators; SiO2, Al2O3, Si3N4, and Ta2O5. The results show that the choice of insulator influences the detection limit, the saturation concentration, and the saturation response. Furthermore, there is a strong correlation between the observed saturation response and the oxygen concentration of the insulator surface, as measured by Auger electron spectroscopy, which indicates that the trapping of hydrogen at the interface occurs at the oxygen atoms of the insulator surface. Finally, if the metal film is porous a catalytic oxidation of the insulator surface appears to be facilitated, which can increase the hydrogen response.

  • 223.
    Eriksson, Mikael
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Waters, Rafael
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Svensson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Isberg, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Leijon, Mats
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Wave power absorption: Experiments in open sea and simulation2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 102, no 8, p. 084910-084910-5Article in journal (Refereed)
    Abstract [en]

    A full scale prototype of a wave power plant based on a direct drive linear generator driven by a point absorber has been installed at the west coast of Sweden. In this paper, experimentally collected data of energy absorption for different electrical loads are used to verify a model of the wave power plant including the interactions of wave, buoy, generator, and external load circuit. The wave-buoy interaction is modeled with linear potential wave theory. The generator is modeled as a nonlinear mechanical damping function that is dependent on piston velocity and electric load. The results show good agreement between experiments and simulations. Potential wave theory is well suited for the modeling of a point absorber in normal operation and for the design of future converters. Moreover, the simulations are fast, which opens up for simulations of wave farms.

  • 224.
    Eriksson, Olle
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Iusan, Diana
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics, Theoretical Magnetism.
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Sanyal, Biplab
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ordering in diluted magnetic semiconductors: A magnetic percolation phenomenon (invited)2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 9, p. 09H114-Article in journal (Refereed)
    Abstract [en]

    We report on first principles calculations that describe the electronic structure, magnetic exchange interactions, and ordering temperatures of diluted magnetic semiconductors. The calculated interatomic exchange couplings are used in a Heisenberg Hamiltonian, and ordering temperatures are calculated with the use of Monte Carlo simulations. The accuracy of the method is analyzed by comparing observed and calculated ordering temperatures of several Mn and Cr doped III-V and II-VI semiconductors. The effect of magnetic percolation is discussed along with clustering phenomena and the effect of strong electron-electron interaction.

  • 225.
    Espenlaub, Andrew C.
    et al.
    Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA..
    Myers, Daniel J.
    Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA..
    Young, Erin C.
    Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA..
    Marcinkevicius, Saulius
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Weisbuch, Claude
    Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA.;IP Paris, Ecole Polytech, CNRS, Lab Phys Matiere Condensee, F-91128 Palaiseau, France..
    Speck, James S.
    Univ Calif Santa Barbara, Dept Mat, Santa Barbara, CA 93106 USA..
    Evidence of trap-assisted Auger recombination in low radiative efficiency MBE-grown III-nitride LEDs2019In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 126, no 18, article id 184502Article in journal (Refereed)
    Abstract [en]

    By studying low radiative efficiency blue III-nitride light emitting diodes (LEDs), we find that the ABC model of recombination commonly used for understanding efficiency behavior in LEDs is insufficient and that additional effects should be taken into account. We propose a modification to the standard recombination model by incorporating a bimolecular nonradiative term. The modified model is shown to be in much better agreement with the radiative efficiency data and to be more consistent than the conventional model with very short carrier lifetimes measured by time-resolved photoluminescence in similar, low radiative efficiency material. We present experimental evidence that a hot carrier-generating process is occurring within these devices, in the form of measurements of forward photocurrent under forward bias. The forward photocurrent, due to hot carrier generation in the active region, is present despite the lack of any "efficiency droop"-the usual signature of band-to-band Auger recombination in high-quality III-nitride LEDs. Hot carrier generation in the absence of band-to-band Auger recombination implies that some other source of hot carriers exists within these low radiative efficiency devices, such as trap-assisted Auger recombination.

  • 226. Esteve, Romain
    et al.
    Schoner, A.
    Reshanov, S. A.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nagasawa, H.
    Advanced oxidation process combining oxide deposition and short postoxidation step for N-type 3C- and 4H-SiC2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 4Article in journal (Refereed)
    Abstract [en]

    The electrical properties of oxides fabricated on n-type 3C-SiC (001) and 4H-SiC (0001) epilayers using an advanced oxidation process combining plasma enhanced deposition and rapid postoxidation steps have been investigated. Three gas atmospheres have been studied for the postoxidation steps: N2O, dry, and wet oxygen (H2O). In comparison, additional oxides using postannealing in pure N-2 have been fabricated. The implementation of wet oxygen resulted. in a significant decrease in the interface traps density, in a reduction of oxide fixed charges and in the increased breakdown field in the case of 3C-SiC. In the case of 4H-SiC the postoxidation in N2O is a superior postprocessing step.

  • 227. Esteve, Romain
    et al.
    Schoner, A.
    Reshanov, S. A.
    Zetterling, Carl-Mikael
    KTH, School of Information and Communication Technology (ICT), Microelectronics and Applied Physics, MAP.
    Nagasawa, H.
    Comparative study of thermally grown oxides on n-type free standing 3C-SiC (001)2009In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 106, no 4Article in journal (Refereed)
    Abstract [en]

    Alternative ways to improve the oxidation process of free standing 3C-SiC (001) are developed and tested with the aim to reduce the fixed and mobile charges in the oxide and at the SiO2/3C-SiC interface. The postoxidation annealing step in wet oxygen (O-2+H-2) is demonstrated to be beneficial for n-type 3C-SiC metal-oxide-semi conductor capacitors resulting in significant reduction in flat band voltage shift, effective oxide charge density, and density of interface traps. The inefficiency of nitridation for the improvement of the oxide quality on 3C-SiC is discussed.

  • 228. Ewing, D.J.
    et al.
    Porter, L.M.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Ma, X.
    Sudharsan, T.S.
    Tumakha, S.
    Goa, M.
    Brillson, L.J.
    Inhomogeneities in Ni4H-SiC Schottky barriers: Localized Fermi-level pinning by defect states2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 11Article in journal (Refereed)
    Abstract [en]

    We investigated arrays of Ni, Pt, or Ti Schottky diodes on n -type 4H-SiC epitaxial layers using current-voltage (I-V) measurements, electron beam induced current (EBIC), polarized light microscopy, x-ray topography, and depth-resolved cathodoluminescence spectroscopy. A significant percentage of diodes (∼7%-30% depending on epitaxial growth method and diode size) displayed "nonideal" or inhomogeneous barrier height characteristics. We used a thermionic emission model based on two parallel diodes to determine the barrier heights and ideality factors of high- and low-barrier regions within individual nonideal diodes. Whereas high-barrier barrier heights increased with metal work function, low-barrier barrier heights remained constant at ∼0.60, 0.85, and 1.05 eV. The sources of these nonidealities were investigated with a variety of spectroscopic and imaging techniques to determine the nature and energy levels of the defects. EBIC indicated that clusters of defects occurred in all inhomogeneous diodes. Cathodoluminescence spectra revealed additional peaks in the nonideal diodes at 2.65, 2.40, and 2.20 eV, which complement the low-barrier barrier heights. It is proposed that defect clusters act to locally pin the Fermi level, creating localized low-barrier patches, which account for the inhomogeneous electrical characteristics. © 2007 American Institute of Physics.

  • 229. Eyrich, C.
    et al.
    Huttema, W.
    Arora, M.
    Montoya, E.
    Rashidi, F.
    Burrowes, C.
    Kardasz, B.
    Girt, E.
    Heinrich, B.
    Mryasov, O. N.
    From, M.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Exchange stiffness in thin film Co alloys2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 7, p. 07C919-Article in journal (Refereed)
    Abstract [en]

    The exchange stiffness (A(ex)) is one of the key parameters controlling magnetization reversal in magnetic materials. We used a method based on the spin spiral formation in two ferromagnetic films antiferromagnetically coupled across a non-magnetic spacer layer and Brillouin scattering to measure A(ex) for a series of Co1-delta X delta (X=Cr, Ni, Ru, Pd, Pt) thin film alloys. The results show that A(ex) of Co alloys does not necessarily scale with M-s; A(ex) approximately decreases at the rate of 1.1%, 1.5%, 2.1%, 3.5%, and 5.6%, while M-s decreases at the rate of 1.1%, 0.5%, 1.1%, 3.7%, and 2.5% per addition of 1 at% of Pt, Ni, Pd, Cr, and Ru, respectively.

  • 230.
    Fager, Hanna
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Tengstrand, Olof
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Bolz, S.
    CemeCon AG, Germany.
    Mesic, B.
    CemeCon AG, Germany.
    Koelker, W.
    CemeCon AG, Germany.
    Schiffers, Ch.
    CemeCon AG, Germany.
    Lemmer, O.
    CemeCon AG, Germany.
    Greene, Joseph E
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Petrov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. University of Illinois, IL 61801 USA; University of Illinois, IL 61801 USA.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Low-temperature growth of dense and hard Ti0.41Al0.51Ta0.08N films via hybrid HIPIMS/DC magnetron co-sputtering with synchronized metal-ion irradiation2017In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 121, no 17, article id 171902Article in journal (Refereed)
    Abstract [en]

    Hard Ti1-xAlxN thin films are of importance for metal-cutting applications. The hardness, thermal stability, and oxidation resistance of these coatings can be further enhanced by alloying with TaN. We use a hybrid high-power pulsed and dc magnetron co-sputtering (HIPIMS/DCMS) technique to grow dense and hard Ti0.41Al0.51Ta0.08N alloys without external heating (T-s amp;lt; 150 degrees C). Separate Ti and Al targets operating in the DCMS mode maintain a deposition rate of similar to 50 nm/min, while irradiation of the growing film by heavy Ta+/Ta2+ ions from the HIPIMS-powered Ta target, using dc bias synchronized to the metal-ion-rich part of each HIPIMS pulse, provides effective near-surface atomic mixing resulting in densification. The substrate is maintained at floating potential between the short bias pulses to minimize Ar+ bombardment, which typically leads to high compressive stress. Transmission and scanning electron microscopy analyses reveal dramatic differences in the microstructure of the co-sputtered HIPIMS/DCMS films (Ta-HIPIMS) compared to films with the same composition grown at floating potential with all targets in the DCMS mode (Ta-DCMS). The Ta-DCMS alloy films are only similar to 70% dense due to both inter-and intra-columnar porosity. In contrast, the Ta-HIPIMS layers exhibit no inter-columnar porosity and are essentially fully dense. The mechanical properties of Ta-HIPIMS films are significantly improved with hardness and elastic modulus values of 28.0 and 328 GPa compared to 15.3 and 289 GPa for reference Ta-DCMS films. Published by AIP Publishing.

  • 231.
    Fagerlind, M.
    et al.
    Chalmers.
    Allerstam, F.
    Chalmers.
    Sveinbjornsson, E.O.
    Chalmers.
    Rorsman, N.
    Chalmers.
    Kakanakova-Georgieva, Anelia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Lundskog, Anders
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Investigation of the interface between silicon nitride passivations and AlGaN/AlN/GaN heterostructures by C(V) characterization of metal-insulator-semiconductor-heterostructure capacitors2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 1, p. 014508-Article in journal (Refereed)
    Abstract [en]

    Capacitance-voltage [C(V)] measurements of metal-insulator-semiconductor-heterostructure capacitors are used to investigate the interface between silicon nitride passivation and AlGaN/AlN/GaN heterostructure material. AlGaN/AlN/GaN samples having different silicon nitride passivating layers, deposited using three different deposition techniques, are evaluated. Different interface state distributions result in large differences in the C(V) characteristics. A method to extract fixed charge as well as traps from the C(V) characteristics is presented. Rough estimates of the emission time constants of the traps can be extracted by careful analysis of the C(V) characteristics. The fixed charge is positive for all samples, with a density varying between 1.3 x 10(12) and 7.1 x 10(12) cm(-2). For the traps, the peak density of interface states is varying between 16 x 10(12) and 31 x 10(12) cm(-2) eV(-1) for the three samples. It is concluded that, of the deposition methods investigated in this report, the low pressure chemical vapor deposited silicon nitride passivation shows the most promising results with regards to low densities of interface states.

  • 232.
    Fallqvist, Amie
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Fager, Hanna
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Self-organization during Growth of ZrN/SiNx Multilayers by Epitaxial Lateral Overgrowth2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 224302Article in journal (Refereed)
    Abstract [en]

    ZrN/SiNx nanoscale multilayers were deposited on ZrN seed layers grown on top of MgO(001) substrates by dc magnetron sputtering with a constant ZrN thickness of 40 Å and with an intended SiNx thickness of 2, 4, 6, 8, and 15 Å at a substrate temperature of 800 °C and 6 Å at 500 °C. The films were investigated by X-ray diffraction, high-resolution scanning transmission electron microscopy, and energy dispersive X-ray spectroscopy. The investigations show that the SiNx is amorphous and that the ZrN layers are crystalline. Growth of epitaxial cubic SiNx – known to take place on TiN(001) – on ZrN(001) is excluded to the monolayer resolution of this study. During the course of SiNx deposition, the material segregates to form surface precipitates in discontinuous layers for SiNx thicknesses ≤ 6 Å that coalesce into continuous layers for 8 and 15 Å thickness at 800 °C, and for 6 Å at 500 °C. The SiNx precipitates are aligned vertically. The ZrN layers in turn grow by epitaxial lateral overgrowth on the discontinuous SiNx in samples deposited at 800 °C with up to 6 Å thick SiNx layers. Effectively a self-organized nanostructure can be grown consisting of strings of 1-3 nm large SiNx precipitates along apparent column boundaries in the epitaxial ZrN.

  • 233.
    Fang, C. M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Ahuja, Rajeev
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Eriksson, Olle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Prediction of MAX phases, VN+1SiCN (N=1,2), from first-principles theory2007In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 101, no 1, p. 013511-Article in journal (Refereed)
    Abstract [en]

    We have investigated the phase stability of two MAX phases, V3SiC2 and V2SiC, by means of first-principles total-energy calculations within the generalized-gradient approximation and the projector-augmented wave method. The theoretical bulk modulus of V3SiC2 is 219 GPa, which is similar to 17% larger than that of Ti3SiC2 (187 GPa). The total-energy calculations show that V2SiC is stable with a formation energy of about 0.27 eVf.u. and that V3SiC2 is metastable (only 0.02 eVf.u. is required to stabilize this phase from its competing phases). We suggest that both these two MAX compounds should be possible to synthesize as stable (or metastable) phases using, e.g., thin-film deposition.

  • 234.
    Fang, Mei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Volotinen, Tarja
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Kulkarni, S. K.
    Indian Institute of Science Education and Research, India.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Rao, K. V.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Engineering Material Physics.
    Enhanced linear sphere size dependence of photonic band gaps for 3D nanocomposite magnetic photonic crystals2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550Article in journal (Other academic)
    Abstract [en]

    Silica spheres in the size range (70-650) nm, containing embedded nano-sized magnetic iron oxide particles have been synthesized and arranged into 3D-face-centered-cubic (fcc) structured magnetic photonic crystals (MPCs) with the (111) crystal plane parallel to the glass substrate surface. Five photonic band gaps (PBGs) are observed in the optical transmission spectra measured over UV-Vis-near IR range for MPCs. The peak wavelengths of the PBGs (λC) are found to increase linearly with the sphere size (Φ). Furthermore, on embedding magnetic nanoparticles the position of PBGs is shifted to higher wavelengths. In addition, the average refractive index, 1.5 ± 0.1, obtained for the MPCs from the slopes of λC(Φ) is found to be larger than the reported value of 1.349 for pure silica PCs.

  • 235. Fang, Mei
    et al.
    Volotinen, Tarja T.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kulkarni, S K
    Belova, Lyubov
    Rao, K V
    Effect of embedding Fe3O4 nanoparticles in silica spheres on the optical transmission properties of three-dimensional magnetic photonic crystals2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 10, p. 103501-Article in journal (Refereed)
    Abstract [en]

    Magnetic and optical properties of three-dimensional fcc-structured magnetic photonic crystals (MPCs), consisting of SiO2 spheres, in the size range 260-680 nm, embedded with 0-6.4 wt % Fe3O4 nanoparticles have been investigated. In the wide spatial angle transmission spectra for these crystals at normal incidence of light in the UV-visible range, five photonic band gaps (PBGs) due to Bragg diffraction from different crystal planes have been observed. The Bragg wavelengths (lambda(B)) of PBGs in both the nonmagnetic and MPCs of the same structure are found to depend linearly on the sphere size. From the slope of this linear function the calculated effective refractive index is found to increase with the concentration of the magnetite nanoparticles in the MPCs, and is consistent with the result calculated from the average dielectric constant. We also find lambda(B) of PBGs are dependent on the angle of the incidence of the light. Furthermore, for small angles this angular dependency is more strongly dependent on the polarization of incident light for MPCs than for the non-MPCs. Thus, magnetic nanocomposite PCs can be designed to incorporate additional functionality in the development of potential magneto-optical devices. c 2010 American Institute of Physics. [doi:10.1063/1.3509146]

  • 236.
    Fang, Mei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Volotinen, Tarja T.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kulkarni, S. K.
    Belova, Lyubov
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Rao, K. Venkat
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of embedding Fe3O4 nanoparticles in silica spheres on the optical transmission properties of three-dimensional magnetic photonic crystals2010In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 108, no 10, p. 103501-Article in journal (Refereed)
    Abstract [en]

    Magnetic and optical properties of three-dimensional fcc-structured magnetic photonic crystals (MPCs), consisting of SiO2 spheres, in the size range 260-680 nm, embedded with 0-6.4 wt % Fe3O4 nanoparticles have been investigated. In the wide spatial angle transmission spectra for these crystals at normal incidence of light in the UV-visible range, five photonic band gaps (PBGs) due to Bragg diffraction from different crystal planes have been observed. The Bragg wavelengths (lambda(B)) of PBGs in both the nonmagnetic and MPCs of the same structure are found to depend linearly on the sphere size. From the slope of this linear function the calculated effective refractive index is found to increase with the concentration of the magnetite nanoparticles in the MPCs, and is consistent with the result calculated from the average dielectric constant. We also find lambda(B) of PBGs are dependent on the angle of the incidence of the light. Furthermore, for small angles this angular dependency is more strongly dependent on the polarization of incident light for MPCs than for the non-MPCs. Thus, magnetic nanocomposite PCs can be designed to incorporate additional functionality in the development of potential magneto-optical devices.

  • 237. Fang, Yeyu
    et al.
    Persson, J.
    Zha, Chaolin
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Willman, J.
    Miller, Casey W.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Material Physics.
    Utility of reactively sputtered CuNx films in spintronics devices2012In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 111, no 7, p. 073912-Article in journal (Refereed)
    Abstract [en]

    We have studied nitrified copper (CuNx) thin films grown by reactive sputtering in the context of spintronic devices. The Ar-to-N-2 flow ratio enables tunability of the electrical resistivity and surface roughness of the CuNx films, with the former increasing to nearly 20 times that of Cu, and the latter reduced to the atomic scale. Incorporating this into a Ta/CuNx/Ta seed stack for spin valves improves the current-in-plane (CIP) magnetoresistance; maximum magnetoresistance results with CuNx seed layer and Cu interlayer. Finally, finite element modeling results are presented that suggest the use of CuNx in nanocontact spin torque oscillators can enhance current densities by limiting the current spread through the device. This may positively impact threshold currents, power requirements, and device reliability.

  • 238.
    Fare, T.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Spetz, Anita
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Armgarth, M.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Reversible interaction of hydrogen with thin layers of thermally grown silicon dioxide1988In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 63, no 11, p. 5507-5513Article in journal (Refereed)
    Abstract [en]

    Some effects of hydrogen on the electrical properties of Pd‐metal‐thin (≊10 nm) oxide‐silicon capacitors are reported. High‐frequency (1 MHz) and quasistatic capacitance voltage curves are measured at 100 °C as a function of hydrogen partial pressure in a background atmosphere of 20% O2/Ar. Besides the standard hydrogen‐induced shift of the capacitance‐voltage characteristics we find: (1) an increase in the accumulation capacitance with increasing hydrogen partial pressure, and (2) a nonmonotonic increase in the quasistatic capacitance minimum with increasing hydrogen pressure. The relative increase in the accumulation capacitance is shown to be related to the square of the hydrogen‐induced voltage shift (and hence to the square of the concentration of hydrogen atoms at the Pd‐SiO2 interface). We discuss our findings, based on existing hydrogen‐silicon dioxide models, to interpret the effects of hydrogen on the high‐frequency and quasistatic capacitance characteristics.

  • 239.
    Felton, Solveig
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Nordblad, Per
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. Fasta tillståndets fysik.
    Ronneteg, Sabina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Berger, Rolf
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics. oorganisk kemi.
    Magnetic properties of TlCu2–xFexSe2 crystals2005In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 97, no 10, p. 10B311-Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of two compositions of random solutions in the TlCu2–xFexSe2 system with x=0.2 and 0.45 have been investigated by superconducting quantum interference device magnetometry. The crystal structure is of a layer type and ordering due to the iron atoms occurs at low temperatures, with Tc=85 K for x=0.2 and Tc=130 K for x=0.45. The samples were highly textured crystals and the magnetic moments of both compositions were found to align along the c axis of the structure. The saturation moments were found to be 1.5µB/Fe for x=0.2 and 0.66µB/Fe for x=0.45.

  • 240.
    Ferreira, da Silva A.
    et al.
    Ferreira da Silva, A., Instituto de Física, Lab. de Propriedades Óticas, Camp. Universitário de Ondina, 40210-340 Salvador, Bahia, Brazil.
    Pepe, I.
    Instituto de Física, Lab. de Propriedades Óticas, Camp. Universitário de Ondina, 40210-340 Salvador, Bahia, Brazil.
    Sernelius, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics .
    Persson, C.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-75121 Uppsala, Sweden, National Renewable Energy Laboratory, Golden, CO 80401.
    Ahuja, R.
    Condensed Matter Theory Group, Department of Physics, Uppsala University, SE-75121 Uppsala, Sweden.
    De, Souza J.P.
    De Souza, J.P., Institute de Física, Univ. Federal do Rio Grande do Sul, 91501970 Porto Alegre, RS, Brazil, Thomas J. Watson Research Center, IBM, Yorktown Heights, NY 10598.
    Suzuki, Y.
    Physics Department, City College, City University of New York, New York 10031.
    Yang, Y.
    Physics Department, City College, City University of New York, New York 10031.
    Electrical resistivity of acceptor carbon in GaAs2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 95, no 5, p. 2532-2535Article in journal (Refereed)
    Abstract [en]

    The resistivity of GaAs implanted with carbon acceptors for concentrations spanning the insulating to the metallic regimes were investigated experimentally and theoretically between room temperature and 1.7 K. The resistivities obtained experimentally were compared with resistivity values calculated from a generalized Drude approach. The value of the critical impurity concentration was found to be about 1018cm-3. Good agreement was obtained between the experimental results and calculations.

  • 241.
    Figueiredo, Nuno M.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sanchez-Garcia, J. A.
    Escobar Galindo, R.
    Climent-Font, A.
    Cavaleiro, A.
    Optical properties and refractive index sensitivity of reactive sputtered oxide coatings with embedded Au clusters2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 6, p. 063512-Article in journal (Refereed)
    Abstract [en]

    In the present study, nanocomposite coatings of Au clusters embedded in two different oxides, TiO2 and Al2O3, were synthesized using pulsed DC magnetron sputtering. The depositions were carried out in three steps, by depositing the oxide, the Au clusters, and again the oxide. The deposition time of the Au clusters was varied in order to achieve different cluster sizes, morphologies, and nanocomposite topographies. The structure, microstructure, morphology, and the optical properties of the coatings were studied. With the increase in Au content, red-shifted surface plasmon resonance (SPR) peaks with higher intensity and increased widths were observed due to changes in the metal clusters sizes and morphology and due to interparticle effects. In order to relate the peculiar SPR extinction bands with the different clusters shapes and distributions, a simulation of the optical properties of the nanocomposites was performed making use of the Renormalized Maxwell-Garnett approach. A theoretical study concerning the refractive index sensitivity was made in order to predict the optimal coatings parameters for sensing experiments. The increased surface area and the strong SPR extinction bands make these coatings suitable for gas sensing and also catalysis, albeit many other application fields can be envisaged.

  • 242.
    Filippini, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Gunnarsson, J.
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Chemical image generation with a grid-gate device2004In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 96, no 12, p. 7583-7590Article in journal (Refereed)
    Abstract [en]

    Scanning light pulse technique generating distinctive chemical images of diverse gases is demonstrated using a sensing arrangement that allows unrestricted choice of sensing materials, disregarding its conductivity or morphology. The present device, a metal oxide semiconductor structure, disentangles biasing from chemical functions by providing an inert grid as a gate that supplies the proper biasing, while functional materials even in the form of disconnected clusters can be used for sensing. The reading of conductimetric chemical responses of clustered materials, in nominal operating conditions, is demonstrated by the generation of chemical images acquired for inversion biasing conditions. © 2004 American Institute of Physics.

  • 243.
    Filippini, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Hydrogen detection on bare SiO2 between metal gates2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 6, p. 3896-3903Article in journal (Refereed)
    Abstract [en]

    Metal-oxide-semiconductor capacitors with gates of Pd and Au forming a wedge of bare SiO2 between them are described. It is observed that the sensitivity to H2 in the wedge is larger than on the outside of the metal gates due to the different distribution of potential determined by the geometrical constraints. The local response of the surface is obtained through the use of a scanning light pulse technique (SLPT), showing photocurrent versus voltage curves shifted to more negative voltages upon exposure to hydrogen. Within the wedge there is a two-dimensional photocurrent pattern composed of two splitting photocurrent peaks, whose separation depends on the distance between Au and Pd contacts, and on the composition of the ambient. The transient response in the wedge is comparable to that of Pd gates and the possibility of detecting hydrogen (or other molecules) by measuring on the bare insulator surface provides new possibilities for the use of field-effect structures for gas sensing. A semiempirical model describing the SLPT response for this particular geometry, conforms to experimental features, and highlights the sensitivity of the distribution of potential in the wedge to the density of charges induced on the semiconductor surface. © 2002 American Institute of Physics.

  • 244.
    Filippini, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Lundström, Ingemar
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Applied Physics .
    Spectral characteristics of computer screen photoassisted classification2006In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 99, no 11Article in journal (Refereed)
    Abstract [en]

    The computer screen photoassisted technique (CSPT) is a practical method for the classification of colored or fluorescent substances such as those present in bioassays but using standard computer sets and regular web cameras as all instruments. It is empirically known that the performance of the CSPT classification depends on the composition of the illuminating sequences displayed by the computer screens during the measurements, and by the way that substance fingerprints from these measurements are composed. Here the illuminating conditions are examined with the help of a CSPT model that allows to examine the physical grounds of optimum illuminating sequences different from just three screen primaries and to assess the limitations and importance of longer illuminating sequences in practical determinations. © 2006 American Institute of Physics.

  • 245.
    Filippov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, X. J.
    National Laboratory for Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai, China .
    Devika, M.
    Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea .
    Koteeswara Reddy, N.
    Department of Nanobio Materials and Electronics, Gwangju Institute of Science and Technology, Gwangju 500712, Republic of Korea.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Effects of Ni-coating on ZnO nanowires: A Raman scattering study2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 21, p. 214302-1-214302-6Article in journal (Refereed)
    Abstract [en]

    Structural properties of ZnO/Ni core/shell nanowires (NWs) are studied in detail by means of Raman spectroscopy. It is shown that formation of the Ni shell leads to passivation of surface states responsible for the observed enhanced intensity of the A1(LO) Raman mode of the bare ZnO NWs. It also causes appearance of 490 cm−1 and 710 cm−1 modes that are attributed to local vibrational modes of a defect/impurity (or defects/impurities). This defect is concluded to be preferably formed in annealed ZnO/Ni NWs and is unlikely to contain a Ni atom, as the same Raman modes were also reported for the Ni-free ZnO nanostructures. From our resonant Raman studies, we also show that the ZnO/Ni core/shell NWs exhibit an enhanced Raman signal with a multiline structure involving A1(LO). This observation is attributed to combined effects of an enhanced Fröhlich interaction at the ZnO/Ni heterointerface and coupling of the scattered light with local surface plasmons excited in the Ni shell. The plasmonic effect is also suggested to allow detection of carbon-related species absorbed at the surface of a single ZnO/Ni NW, promising for applications of such structures as efficient nano-sized gas sensors.

  • 246. Fogelberg, J.
    et al.
    Eriksson, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Dannetun, Helen
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Petersson, L.-G.
    Kinetic modelling of hydrogen ad/absorption in thin films of hydrogen sensitive field effect devices: Observation of large hydrogen induced dipoles at the Pd/SiO2 interface1995In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, ISSN 0021-8979, Vol. 78, p. 988-Article in journal (Refereed)
    Abstract [en]

    A kinetic modeling of the hydrogen interaction with a Pd‐SiO2‐Si (Pd‐MOS) device is reported. The model is fitted to a number of experimental results, mainly from mass spectrometric desorption measurements. The new results verify an older description of the energetics of hydrogen adsorption states at the Pd/SiO2 interface in the sense that the adsorption may be described by a so‐called Temkin isotherm; however, several new findings have to be incorporated into the model in order to obtain a consistent picture. The initial heat of adsorption at the interface is around 0.8 eV/hydrogen atom. The number of adsorption sites at the interface is considerably smaller than at the surface, 6×1017 m−2 versus 1.5×1019 m−2. Furthermore, the interface hydrogen atoms are strongly polarized. An average value of 2 Debye is obtained. It is the large hydrogen polarization at the Pd/SiO2 interface and not a large concentration of adsorbed hydrogen atoms per se which accounts for the very high sensitivity of a Pd‐MOS device as hydrogen sensor

  • 247.
    Fogelqvist, Emelie
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Kördel, Mikael
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Selin, Mårten
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Hertz, Hans M.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Biomedical and X-ray Physics.
    Stability of liquid-nitrogen-jet laser-plasma targets2015In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 118, no 17, article id 174902Article in journal (Refereed)
    Abstract [en]

    Microscopic jets of cryogenic substances such as liquid nitrogen are important regenerative high-density targets for high-repetition rate, high-brightness laser-plasma soft x-ray sources. When operated in vacuum such liquid jets exhibit several non-classical instabilities that negatively influence the x-ray source's spatial and temporal stability, yield, and brightness, parameters that all are important for applications such as water-window microscopy. In the present paper, we investigate liquid-nitrogen jets with a flash-illumination imaging system that allows for a quantitative stability analysis with high spatial and temporal resolution. Direct and indirect consequences of evaporation are identified as the key reasons for the observed instabilities. Operating the jets in an approximately 100 mbar ambient atmosphere counteracts the effects of evaporation and produces highly stable liquid nitrogen jets. For operation in vacuum, which is necessary for the laser plasmas, we improve the stability by introducing an external radiative heating element. The method significantly extends the distance from the nozzle that can be used for liquid-jet laser plasmas, which is of importance for high-average-power applications. Finally, we show that laser-plasma operation with the heating-element-stabilized jet shows improved short-term and long-term temporal stability in its water-window x-ray emission.

  • 248.
    Forsén, Rikard
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Ghafoor, Naureen
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 114, no 24, p. 244303-Article in journal (Refereed)
    Abstract [en]

    A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti 1−x Cr x N multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti- and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti 1−x Cr x N layers. For x = 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > =0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials.

  • 249. Fraerman, A. A.
    et al.
    Gribkov, B. A.
    Gusev, S. A.
    Klimov, A. Yu.
    Mironov, V. L.
    Nikitushkin, D. S.
    Rogov, V. V.
    Vdovichev, S. N.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
    Zabel, H.
    Magnetic force microscopy of helical states in multilayer nanomagnets2008In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 103, no 7, p. 073916-Article in journal (Refereed)
    Abstract [en]

    We have used magnetic force microscopy (MFM) to investigate noncollinear helical states in multilayer nanomagnets, consisting of a stack of single domain ferromagnetic disks separated by insulating nonmagnetic spacers. The nanomagnets were fabricated from a [Co/Si]x3 multilayer thin film structure by electron beam lithography and ion beam etching. The structural parameters (Co layer and spacer thicknesses) were optimized to obtain a clear spiral signature in the MFM contrast, taking into account the magnetostatic interaction between the layers. MFM contrast corresponding to the helical states with different helicities was observed for the optimized structure with Co layer thicknesses of 16, 11, and 8 nm, and with 3 nm Si spacer thickness.

  • 250.
    Frenning, Göran
    et al.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Jonsson, AnnaKarin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Larsson, A.-L.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Strömme, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Materials Science.
    Theoretical investigation of ion conduction in three-layered ion-conductor systems: Derivation of the isothermal transient ionic current and frequency-dependent impedance2003In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 94, p. 1629-Article in journal (Refereed)
    Abstract [en]

    Ion conduction in three-layered ion-conductor systems is considered. Explicit analytic expressions for the isothermal transient ionic current and frequency-dependent impedance are derived. The analysis includes migration, diffusion and space-charge effects as contributors to the ionic motion. The resulting model allows conduction parameters such as diffusion coefficients and ion concentrations in three different layers to be obtained from one single measurement, either in the time or in the frequency domain. The implications of one or more of the layers being mixed ionic/electronic conductors are discussed, and it is argued that the proposed model provides a useful description of the coupled ionic/electronic motion occurring in such a mixed-conductor system.

2345678 201 - 250 of 979
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