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  • 51.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ivanov, Ivan Gueorguiev
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Toropov, A. A.
    Terentev, Ya. V.
    Sorokin, S. V.
    Lebedev, A. V.
    Ivanov, S. V.
    Kopev, P. S.
    Tunable laser spectroscopy of spin injection in ZnMnSe/ZnCdSe quantum structures2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 12, p. 2196-Article in journal (Refereed)
    Abstract [en]

     Magneto-optical spectroscopy in combination with tunable laser excitation is employed to study exciton spin alignment and injection in ZnMnSe/ZnCdSe quantum structures. This approach enables us to selectively create preferred spin orientation and to separately monitor subsequent spin injection from individual spin states, thus shedding light on a possible source of spin loss. It is shown that the limited spin polarization in a nonmagnetic quantum well due to spin injection from a ZnMnSe-based diluted magnetic semiconductor (DMS) is not caused by a limited degree of spin alignment in the DMS, which is in fact complete, but rather occurs during subsequent processes.

  • 52.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Izadifard, M.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hong, Y.G.
    Tu, C.W.
    Modeling of band gap properties of GaInNP alloys lattice matched to GaAs2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 3, p. 31907-Article in journal (Refereed)
    Abstract [en]

    Compositional and temperature dependences of the band gap energies of GaInNP alloys, which are lattice matched to GaAs, are determined and modeled by a band anticrossing (BAC) interaction between the localized state of the isolated NP and extended host states. The BAC parameters are deduced as EN =2.1±0.1 eV and CMN =1.7±0.2 eV. The low value of the coupling parameter CMN implies weaker coupling of the N level with the host matrix, presumably due to short range ordering effects, similar to the case of GaInNAs alloys with a high In content. The obtained information is important for future modeling of the electronic structure of the alloys. © 2006 American Institute of Physics.

  • 53.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Izadifard, Morteza
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kim, J.
    Ren, F.
    Thaler, G.
    Abernathy, C. R.
    Pearton, S. J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J. Y.
    Zavada, J. M.
    On the origin of spin loss in GaMnN/InGaN Light-Emitting Diodes2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, p. 2599-Article in journal (Refereed)
    Abstract [en]

     Spin polarization of GaMnN/InGaN light-emitting diodes grown by molecular beam epitaxy is analyzed. In spite of the ferromagnetic behavior of the GaMnN spin injector, the diodes are shown to exhibit very low efficiency of spin injection. Based on resonant optical orientation spectroscopy, the spin loss in the structures is shown to be largely due to fast spin relaxation within the InGaN spin detector, which itself destroys any spin polarization generated by optical spin orientation or electrical spin injection.

  • 54.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Izadifard, Morteza
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Polimeni, A.
    Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza,” Roma, Italy.
    Capizzi, M.
    Istituto Nazionale di Fisica della Materia, Dipartimento di Fisica, Università degli Studi di Roma “La Sapienza,” Roma, Italy.
    Xin, H. P.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California.
    Hydrogen-induced improvements in optical quality of GaNAs alloys2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 21, p. 3662-3665Article in journal (Refereed)
    Abstract [en]

    Strong suppression of potential fluctuations in the band edges of GaNAs alloys due to postgrowth hydrogen treatment, which is accompanied by a reopening of the alloy band gap, is revealed from temperature-dependent photoluminescence (PL) and PL excitation measurements. The effect likely indicates preferential trapping of hydrogen near the lattice sites with the highest nitrogen content. A remarkable improvement in the radiative efficiency of the alloys at room temperature is also demonstrated and is ascribed to efficient hydrogen passivation of competing nonradiative centers.

  • 55.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Tu, C. W.
    Time-resolved studies of photoluminescence in GaNxP1-x alloys: Evidence for indirect-direct band gap crossover2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, no 1, p. 52-Article in journal (Refereed)
    Abstract [en]

     Time resolved photoluminescence spectroscopy is employed to monitor the effect of N incorporation on the band structure of GaNP alloys. Abrupt shortening in radiative lifetime of near-band gap emissions, arising from excitonic radiative recombination within N-related centers, is found to occur at very low N compositions of around 0.5%, i.e., within the same range as the appearance of the direct-band gap-like transitions in the photomodulated transmission spectra of GaNP reported previously. The effect has been attributed to an enhancement in oscillator strength of optical transitions due to band crossover from indirect to direct-band gap of the alloy.

  • 56.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, Galia
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Hai, P. N.
    Thinh, N. Q.
    Bergman, Peder
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Tu, C. W.
    Mechanism for rapid thermal annealing improvements in undoped GaNxAs1-x/GaAs structures grown by molecular beam epitaxy2000In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 77, no 15, p. 2325-Article in journal (Refereed)
    Abstract [en]

     A systematic investigation of the effect of rapid thermal annealing (RTA) on optical properties of undoped GaNAs/GaAs structures is reported. Two effects are suggested to account for the observed dramatic improvement in the quality of the GaNxAs1-x/GaAs quantum structures after RTA: (i) improved composition uniformity of the GaNxAs1-x alloy, deduced from the photoluminescence (PL), PL excitation and time-resolved measurements; and (ii) significant reduction in the concentration of competing nonradiative defects, revealed by the optically detected magnetic resonance studies.

  • 57.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Rudko, G. Yu.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Toropov, A. A.
    Sorokin, S. V.
    Ivanov, S. V.
    Kopev, P. S.
    Control of spin functionality in ZnMnSe-based structures: Spin switching versus spin alignment2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 11, p. 1700-Article in journal (Refereed)
    Abstract [en]

     The ability of attaining desired spin functionality by adjusting structural design is demonstrated in diluted magnetic semiconductor (DMS) quantum structures based on II-VI semiconductors. The following spin enabling functions are achieved by tuning the ratio between the rates of exciton spin relaxation within the DMS and exciton escape from it to an adjacent nonmagnetic spin detector. Spin switching is realized when using a thin layer of Zn0.95Mn0.05Se as a spin manipulator and is attributed to a fast exciton escape from the DMS preceding the spin relaxation. Spin alignment is accomplished in tunneling structures where the presence of an energy barrier inserted between a spin manipulator (a DMS-based superlattice) and a spin detector ensures a slow escape rate from the DMS layer.

  • 58.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Rudko, G. Yu.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Xin, H. P.
    Tu, C. W.
    Radiative recombination mechanism in GaNxP1-x alloys2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 80, p. 1740-Article in journal (Refereed)
    Abstract [en]

     Based on the results of temperature-dependent photoluminescence (PL) and absorption measurements, the PL emission in GaNP epilayers and GaNP/GaP multiple quantum well structures with N composition up to 4% is shown to be dominated by optical transitions within deep states likely related to N clusters. With increasing N composition, these states are shown to become resonant with conduction band of the alloy and thus optically inactive, leading to the apparent redshift of the PL maximum position.

  • 59.
    Buyanova, Irina
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Wang, Xingjun
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Pozina, G.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Lim, W.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Norton, D. P.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Pearton, S. J.
    Department of Materials Science and Engineering University of Florida, Gainesville, Florida 32611, USA.
    Osinsky, A.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Dong, J. W.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Hertog, B.
    SVT Associates Eden Prairie, Minnesota 55344, USA.
    Effects of hydrogen on the optical properties of ZnCdO/ZnO quantum wells grown by molecular beam epitaxy2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, p. 261912-Article in journal (Refereed)
    Abstract [en]

    Temperature-dependent cw- and time-resolved photoluminescence (PL), as well as optically detected magnetic resonance (ODMR) measurements are employed to evaluate effects of deuterium (2H) doping on optical properties of ZnCdO/ZnO quantum well structures grown by molecular beam epitaxy. It is shown that incorporation of 2H from a remote plasma causes a substantial improvement in radiative efficiency of the investigated structures. Based on transient PL measurements, the observed improvements are attributed to efficient passivation by hydrogen of competing nonradiative recombination centers via defects. This conclusion is confirmed from the ODMR studies.

  • 60.
    Cakir, Deniz
    et al.
    University of Twente.
    Bokdam, Menno
    University of Twente.
    de Jong, Michel P
    University of Twente.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Brocks, Geert
    University of Twente.
    Modeling charge transfer at organic donor-acceptor semiconductor interfaces2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, no 20, p. 203302-Article in journal (Refereed)
    Abstract [en]

    We develop an integer charge transfer model for the potential steps observed at interfaces between donor and acceptor molecular semiconductors. The potential step can be expressed as the difference between the Fermi energy pinning levels of electrons on the acceptor material and holes on the donor material, as determined from metal-organic semiconductor contacts. These pinning levels can be obtained from simple density functional theory calculations.

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  • 61.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nordblad, Per
    Department of Engineering Sciences, Uppsala University, S-751 21 Uppsala, Sweden.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Air-stable organic-based semiconducting room temperature thin film magnet for spintronics applications2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, no 16, p. 163308-Article in journal (Refereed)
    Abstract [en]

    Herein, we report on a preparation method of vanadium tetracyanoethylene, V(TCNE)x, an organic-based semiconducting room temperature thin film magnet. Previously, this compound has been reported to be extremely air sensitive but this preparation method leads to V(TCNE)x, which can retain its magnetic ordering at least several weeks in air. The electronic structure has been studied by photoelectron spectroscopy and the magnetic properties by superconducting quantum interference device. The properties mentioned above, in combination with complete spin polarization, makes this air-stable V(TCNE)x a very promising material for spintronic devices.

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  • 62.
    Chang, KC
    et al.
    Carnegie Mellon Univ, Dept Mat Sci & Engn, Pittsburgh, PA 15213 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Nuhfer, NT
    Carnegie Mellon Univ, Dept Mat Sci & Engn, Pittsburgh, PA 15213 USA Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Porter, Lisa
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Wahab, Qamar Ul
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    High-carbon concentrations at the silicon dioxide-silicon carbide interface identified by electron energy loss spectroscopy2000In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 77, no 14, p. 2186-2188Article in journal (Refereed)
    Abstract [en]

    High carbon concentrations at distinct regions at thermally-grown SiO2/6H-SiC(0001) interfaces have been detected by electron energy loss spectroscopy (EELS). The thickness of these C-rich regions is estimated to be 10-15 Angstrom. The oxides were grown on n-type 6H-SiC at 1100 degrees C in a wet O-2 ambient for 4 h immediately after cleaning the substrates with the complete RCA process. In contrast, C-rich regions were not detected from EELS analyses of thermally grown SiO2/Si interfaces nor of chemical vapor deposition deposited SiO2/SiC interfaces. Silicon-rich layers within the SiC substrate adjacent to the thermally grown SiO2/SiC interface were also evident. The interface state density D-it in metal-oxide-SiC diodes (with thermally grown SiO2) was approximately 9x10(11) cm(-2) eV(-1) at E- E-v=2.0 eV, which compares well with reported values for SiC metal-oxide-semiconductor (MOS) diodes that have not received a postoxidation anneal. The C-rich regions and the change in SiC stoichiometry may be associated with the higher than desirable D-it's and the low channel mobilities in SiC-based MOS field effect transistors. (C) 2000 American Institute of Physics. [S0003-6951(00)01940-9].

  • 63.
    Chen, Jr-Tai
    et al.
    SweGaN AB, Teknikringen 8D, Linköping, Sweden.
    Bergsten, Johan
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden.
    Lu, Jun
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Janzén, Erik
    SweGaN AB, Teknikringen 8D, Linköping, Sweden.
    Thorsell, Mattias
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Rorsman, Niklas
    Department of Microtechnology and Nanoscience, Chalmers University of Technology, Gothenburg, Sweden.
    Kordina, Olof
    SweGaN AB, Teknikringen 8D, Linköping, Sweden.
    A GaN-SiC hybrid material for high-frequency and power electronics2018In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 113, no 4, article id 041605Article in journal (Refereed)
    Abstract [en]

    We demonstrate that 3.5% in-plane lattice mismatch between GaN (0001) epitaxial layers and SiC (0001) substrates can be accommodated without triggering extended defects over large areas using a grain-boundary-free AIN nucleation layer (NL). Defect formation in the initial epitaxial growth phase is thus significantly alleviated, confirmed by various characterization techniques. As a result, a high-quality 0.2-mu m thin GaN layer can be grown on the AIN NL and directly serve as a channel layer in power devices, like high electron mobility transistors (HEMTs). The channel electrons exhibit a state-of-the-art mobility of amp;gt;2000 cm(2)/V-s, in the AlGaN/GaN heterostructures without a conventional thick C- or Fe-doped buffer layer. The highly scaled transistor processed on the heterostructure with a nearly perfect GaN-SiC interface shows excellent DC and microwave performances. A peak RF power density of 5.8 W/mm was obtained at V-DSQ = 40 V and a fundamental frequency of 30 GHz. Moreover, an unpassivated 0.2-mu m GaN/AIN/SiC stack shows lateral and vertical breakdowns at 1.5 kV. Perfecting the GaN-SiC interface enables a GaN-SiC hybrid material that combines the high-electron-velocity thin GaN with the high-breakdown bulk SiC, which promises further advances in a wide spectrum of high-frequency and power electronics.

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  • 64.
    Chen, Jr-Tai
    et al.
    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.
    Impact of residual carbon on two-dimensional electron gas properties in AlxGa1−xN/GaN heterostructure2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 19, p. 193506-Article in journal (Refereed)
    Abstract [en]

    High tuneability of residual carbon doping is developed in a hot-wall metalorganic chemical vapor deposition reactor. Two orders of temperature-tuned carbon concentration, from ∼2 × 1018 cm−3 down to ∼1 × 1016 cm−3, can be effectively controlled in the growth of the GaN buffer layer. Excellent uniformity of two-dimensional electron gas (2DEG) properties in AlxGa1−xN/AlN/GaN heterostructure with very high average carrier density and mobility, 1.1 × 1013 cm−2 and 2035 cm2/V·s, respectively, over 3" semi-insulating SiC substrate is realized with the temperature-tuned carbon doping scheme. Reduction of carbon concentration is evidenced as a key to achieve high 2DEG carrier density and mobility.

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  • 65.
    Chen, Jr-Tai
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Persson, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nilsson, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Hsu, Chih-Wei
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Forsberg, Urban
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. 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.
    Janzén, Erik
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Room-Temperature mobility above 2200 cm2/V.s of two-dimensional electron gas in a sharp-interface AlGaN/GaN heterostructure2015In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, no 25, article id 251601Article in journal (Refereed)
    Abstract [en]

    A high mobility of 2250 cm2/V·s of a two-dimensional electron gas (2DEG) in a metalorganic chemical vapor deposition-grown AlGaN/GaN heterostructure was demonstrated. The mobility enhancement was a result of better electron confinement due to a sharp AlGaN/GaN interface, as confirmed by scanning transmission electron microscopy analysis, not owing to the formation of a traditional thin AlN exclusion layer. Moreover, we found that the electron mobility in the sharp-interface heterostructures can sustain above 2000 cm2/V·s for a wide range of 2DEG densities. Finally, it is promising that the sharp-interface AlGaN/GaN heterostructure would enable low contact resistance fabrication, less impurity-related scattering, and trapping than the AlGaN/AlN/GaN heterostructure, as the high-impurity-contained AlN is removed.

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  • 66.
    Chen, Miaoxiang
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Perzon, Erik
    Department of Materials and Surface Chemistry, Polymer Technology, Chalmers University of Technology, Göteborg, Sweden .
    Andersson, Mats R
    Department of Materials and Surface Chemistry, Polymer Technology, Chalmers University of Technology, Göteborg, Sweden .
    Pullerits, Tönu
    Department of Chemical Physics, Lund University, Lund, Sweden .
    Andersson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    High carrier mobility in low band gap polymer-based field-effect transistors2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 25, p. 252105-1-252105-3Article in journal (Refereed)
    Abstract [en]

    A conjugated polymer with a low band gap of 1.21 eV, i.e., absorbing infrared light, is demonstrated as active material in field-effect transistors (FETs). The material consists of alternating fluorene units and low band gap segments with electron donor-acceptor-donor units composed of two electron-donating thiophene rings attached on both sides of a thiadiazolo-quinoxaline electron-acceptor group. The polymer is solution-processable and air-stable; the resulting FETs exhibit typical p-channel characteristics and field-effect mobility of 0.03 cm2 V−1 s−1.

  • 67.
    Chen, Miaoxiang
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Nilsson, David
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kugler, Thomas
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Remonen, Tommie
    Acreo AB, Norrköping, Sweden.
    Electric current rectification by an all-organic electrochemical device2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 81, p. 2011-2013Article in journal (Refereed)
    Abstract [en]

    An all-organic printed electrochemical rectifier is reported. The device is based on a patterned layer of poly(3,4-ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS) that interfaces a patterned electrolyte top layer. Overlap between the electrolyte layer and the conducting polymer pattern results in the formation of two electrochemically active areas within the conducting polymer pattern. When bias voltage is applied across the conducting polymer pattern, the PEDOT in the negatively biased areas is reduced electrochemically, while the PEDOT in the positively biased area is further oxidized. Reducing PEDOT from its p-doped, pristine state to the neutral state results in a marked loss of electrical conductivity. Due to the unsymmetrical device geometry, the current through the device may be shut off for one polarity of applied bias voltage with an electrical current rectification ratio of 100 compared to the opposite polarity. The output characteristics of a corresponding half wave rectifier as well as those from a full wave bridge rectifier show stable performance at frequencies below 15 Hz.

  • 68.
    Chen, Miaoxiang
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Perzon, Erik
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden .
    Andersson, Mats R.
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden .
    Marcinkevicius, Saulius
    Department of Microelectronics and Information Technology, Royal Institute of Technology, Kista, Sweden .
    Jönsson, Stina
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    1 micron wavelength photo- and electroluminescence from a conjugated polymer2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 18, p. 3570-3572Article in journal (Refereed)
    Abstract [en]

    We report photo- and electroluminescence from an alternating conjugated polymer consisting of fluorene units and low-band gap donor-acceptor-donor (D–A–D) units. The D–A–D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of 1.27 eV. The corresponding electro- and photoluminescence spectra both peak at approximately 1 μm. Light-emitting diodes, based on a single layer of the polymer, demonstrated external quantum efficiencies from 0.03% to 0.05%.

  • 69.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    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.
    Donor bound excitons involving a hole from the B valence band in ZnO: Time resolved and magneto-photoluminescence studies2011In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 99, no 9, p. 091909-Article in journal (Refereed)
    Abstract [en]

    Time-resolved and magneto-photoluminescence (PL) studies are performed for the so-called I(6)(B) and I(7)(B) excitonic transitions, previously attributed to neutral donor bound excitons involving a hole from the B valence band (VB), D(0)X(B). It is shown that PL decays of these emissions at 2 K are faster than that of their I(6) and I(7) counterparts involving an A VB hole, which is interpreted as being due to energy relaxation of the hole assisted by acoustic phonons. From the magneto-PL measurements, values of effective Lande g factors for conduction electrons and B VB holes are determined as g(e) = 1.91, g(h)(parallel to) = 1.79, and g(h)(perpendicular to) = 0, respectively.

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  • 70.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    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.
    Dynamics of donor bound excitons in ZnO2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 12, p. 121103-Article in journal (Refereed)
    Abstract [en]

    Comprehensive time-resolved photoluminescence measurements are performed on shallow neutral donor bound excitons (D0Xs) in bulk ZnO. It is found that transients of the no-phonon D0X transitions (I6-I9 lines) are largely affected by excitation conditions and change from a bi-exponential decay with characteristic fast (τf) and slow (τs) time constants under above-bandgap excitation to a single exponential one, determined by τs, under two-photon excitation. The slow decay also dominates transients of longitudinal optical phonon-assisted and two-electron-satellite D0X transitions, and is attributed to “bulk” D0X lifetime. The fast component is tentatively suggested to represent effects of surface recombination.

  • 71.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ishikawa, Fumitaro
    Ehime University, Japan.
    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.
    Origin of radiative recombination and manifestations of localization effects in GaAs/GaNAs core/shell nanowires2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 105, no 25, p. 253106-Article in journal (Refereed)
    Abstract [en]

    Radiative carrier recombination processes in GaAs/GaNAs core/shell nanowires grown by molecular beam epitaxy on a Si substrate are systematically investigated by employing micro-photoluminescence (mu-PL) and mu-PL excitation (mu-PLE) measurements complemented by time-resolved PL spectroscopy. At low temperatures, alloy disorder is found to cause localization of photo-excited carriers leading to predominance of optical transitions from localized excitons (LE). Some of the local fluctuations in N composition are suggested to lead to strongly localized three-dimensional confining potential equivalent to that for quantum dots, based on the observation of sharp and discrete PL lines within the LE contour. The localization effects are found to have minor influence on PL spectra at room temperature due to thermal activation of the localized excitons to extended states. Under these conditions, photo-excited carrier lifetime is found to be governed by non-radiative recombination via surface states which is somewhat suppressed upon N incorporation. (C) 2014 AIP Publishing LLC.

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  • 72.
    Chen, Shula
    et al.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Kiba, T.
    Kitami Institute of Technology, Kitami Hokkaido, Japan.
    Yang, Xiaojie
    Suzhou QiangMing Optoelectronics Co. Ltd., Suzhou, China.
    Takayama, J.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Murayama, A.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Power-dependent spin amplification in (In, Ga)As/GaAs quantum well via Pauli blocking by tunnel-coupled quantum dot ensembles2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 15, article id 152103Article in journal (Refereed)
    Abstract [en]

    Power-dependent time-resolved optical spin orientation measurements were performed on In0.1Ga0.9As quantum well(QW) and In0.5Ga0.5As quantum dot (QD) tunnel-coupled structures with an 8-nm-thick GaAs barrier. A fast transient increase of electron spin polarization was observed at the QW ground state after circular-polarized pulse excitation. The temporal maximum of polarization increased with increasing pumping fluence owing to enhanced spin blocking in the QDs, yielding a highest amplification of 174% with respect to the initial spin polarization. Further elevation of the laser power gradually quenched the polarizationdynamics, which was induced by saturated spin filling of both the QDs and the QW phase spaces.

  • 73.
    Chen, Shula
    et al.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Kiba, T.
    Kitami Institute of Technology, Kitami, Hokkaido, Japan.
    Yang, Xiaojie
    Suzhou QiangMing Optoelectronics Co. Ltd., Suzhou, China.
    Takayama, J.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Murayama, A.
    Graduate School of Information Science and Technology, Hokkaido University, Kita-ku, Sapporo, Japan.
    Temperature-dependent spin injection dynamics in InGaAs/GaAs quantum well-dot tunnel-coupled nanostructures2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 119, article id 115701Article in journal (Refereed)
    Abstract [en]

    Time-resolved optical spin orientation spectroscopy was employed to investigate the temperature-dependent electron spin injection in In0.1Ga0.9As quantum well (QW) and In0.5Ga0.5As quantum dots (QDs) tunnel-coupled nanostructures with 4, 6, and 8 nm-thick GaAs barriers. The fast picosecond-ranged spin injection from QW to QDexcited states (ES) was observed to speed up with temperature, as induced by pronounced longitudinal-optical (LO)-phonon-involved multiple scattering process, which contributes to a thermally stable and almost fully spin-conserving injection within 5–180 K. The LO-phonon coupling was also found to cause accelerated electron spin relaxation of QD ES at elevated temperature, mainly via hyperfine interaction with random nuclear field.

  • 74.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kyun Lee, Sun
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dong, H X
    Fudan University.
    Sun, L
    Fudan University.
    Chen, Z H
    Fudan University.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    On the origin of suppression of free exciton no-phonon emission in ZnO tetrapods2010In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 96, no 3, p. 033108-Article in journal (Refereed)
    Abstract [en]

    Temperature dependent photoluminescence and cathodoluminescence (CL) spectroscopies are employed to investigate free exciton (FX) emissions in ZnO tetrapods. The intensity of the no-phonon line is found to be largely suppressed as compared with longitudinal optical phonon assisted transitions, in sharp contrast to bulk ZnO. From spatially resolved CL studies, this suppression is shown to strongly depend on structural morphology of the ZnO tetrapods and becomes most significant within areas with faceted surfaces. A model based on reabsorption due to multiple internal reflections in the vicinity of the FX resonance is suggested to account for the observed effect.

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  • 75.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kayanuma, K.
    Chen, Z. H.
    Murayama, A.
    Oka, Y.
    Toropov, A. A.
    Sorokin, S. V.
    Ivanov, S. V.
    Kopev, P. S.
    Efficient spin depolarization in ZnCdSe spin detector: an important factor limiting optical spin injection efficiency in ZnMnSe/CdZnSe spin light-emitting structures2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 85, p. 5260-Article in journal (Refereed)
    Abstract [en]

     Spin depolarization of a ZnCdSe quantum-well spin detector (SD) in ZnMnSe/ZnCdSe light-emitting quantum structures is investigated by cw and time-resolved optical orientation spectroscopy. It is shown that spin depolarization is governed by three distinct spin relaxation processes with the corresponding polarization decay times of 850, 30, and <10 ps. The dominant and the fastest process is attributed to spin relaxation accompanying energy relaxation of hot excitons (and hot carriers) within the SD, providing evidence that it can be an important source of spin loss, leading to the observed limited efficiency of optical spin injection in the structures.

  • 76.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Murayama, A.
    Furuta, T.
    Oka, Y.
    Norton, D. P.
    Pearton, S. J.
    Osinsky, A.
    Dong, J. W.
    Dominant factors limiting efficiency of optical spin detection in ZnO-based materials2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 92, p. 092103-Article in journal (Refereed)
    Abstract [en]

    Two dominant factors limiting efficiency of optical spin detection in ZnO-based materials system are identified from time-resolved optical orientation and magneto-optical studies. The first is related to the fundamental band structure of the materials characterized by a weak spin-orbit interaction. It leads to cancellation of circular polarization from the optical transitions between the conduction band and the A and B valence band states, which would otherwise carry the desired information on spin polarization of carriers. The second limiting factor is shown to be efficient carrier/exciton spin relaxation, i.e., about 45-80 ps.

  • 77.
    Chen, Weimin
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Nishibayashi, K.
    Kayanuma, K.
    Seo, K.
    Murayama, A.
    Oka, Y.
    Thaler, G.
    Frazier, R.
    Abernathy, C.R.
    Ren, F.
    Pearton, S.J.
    Pan, C.-C.
    Chen, G.-T.
    Chyi, J.-I
    Efficient spin relaxation in InGaN/GaN and InGaN/GaMnN quantum wells: An obstacle to spin detection2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 19, p. 192107-Article in journal (Refereed)
    Abstract [en]

    Transient magneto-optical spectroscopy of InGaNGaN and InGaNGaMnN quantum wells reveals a spin relaxation process with a characteristic time of 50 ps. We show that the observed spin relaxation is mediated by spin flips of individual carriers rather than by direct exciton spin flips, and is proposed to occur near the bottom of the exciton band (K=0). Nearly complete thermalization between spin sublevels of the excitons, observed immediately after the pulsed photoexcitation, is attributed to even faster spin relaxation of photogenerated hot carriers/excitons accompanying momentum and energy relaxation at high K vectors. © 2005 American Institute of Physics.

  • 78.
    Chen, X. Y.
    et al.
    Nanjing University, Peoples R China.
    Yu, T.
    Nanjing University, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, The Institute of Technology.
    Zhang, H. T.
    Nanjing University, Peoples R China.
    Liu, L. F.
    Nanjing University, Peoples R China.
    Wang, Y. M.
    Nanjing University, Peoples R China.
    Li, Z. S.
    Nanjing University, Peoples R China.
    Zou, Z. G.
    Nanjing University, Peoples R China.
    Liu, J.-M.
    Nanjing University, Peoples R China.
    Application of weak ferromagnetic BiFeO3 films as the photoelectrode material under visible-light irradiation2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 2, p. 022114-Article in journal (Refereed)
    Abstract [en]

    BiFeO3 films prepared by pulsed laser deposition on Pt/TiO2/SiO2/Si substrates were studied as photoelectrode for water splitting. Under visible-light irradiation, the photocurrent intensity of the polycrystalline BiFeO3 film was found to double that of the amorphous one in a three-electrode cell. The incident photon to current conversion efficiency for the polycrystalline BiFeO3 electrode was approximately 16% at 350 nm and 7% at 530 nm at 1.5 V (versus saturated calomel electrode). The ferromagnetism of the amorphous BiFeO3 film was an order of magnitude weaker than that of the polycrystalline one, supporting the "size effect" explanation for magnetic origin. (C) 2007 American Institute of Physics.

  • 79.
    Chen, Yen-Ting
    et al.
    Academic Sinica, Taiwan .
    Araki, Tsutomu
    Ritsumeikan University, Japan .
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Persson, Per O A
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chen, Li-Chyong
    National Taiwan University, Taiwan .
    Chen, Kuei-Hsien
    Academic Sinica, Taiwan .
    Holtz, Per-Olof
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Birch, Jens
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Nanishi, Yasushi
    Ritsumeikan University, Japan .
    Nucleation of single GaN nanorods with diameters smaller than 35 nm by molecular beam epitaxy2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 103, no 20, p. 203108-Article in journal (Refereed)
    Abstract [en]

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

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  • 80.
    Chiragwandi, Z.
    et al.
    Göteborg University.
    Gillepsie, K.
    Göteborg University.
    Zhao, Q.X.
    Göteborg University.
    Willander, Magnus
    Göteborg University.
    Panas, I.
    Chalmers University of Technology.
    Ultraviolet driven negative current and rectifier effect in self assembled green fluorescent protein devices2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 16, p. 162909-1-162909-3Article in journal (Refereed)
    Abstract [en]

        UV induced negative current produced at low voltages is reported in a photocurrent rectifier device consisting of a sensing region between two nano Al/Al2O3 electrodes placed 30 nm apart, employing a droplet of enhanced green fluorescent protein as molecular electrolyte. The current-voltage characteristics are discussed in terms of the properties of the thin Al2O3 scale, the position of the Fermi level, the position of the highest occupied molecular orbital-lowest unoccupied molecular orbital gap, and dispersion of states induced by varying dielectric constants

  • 81.
    Chiragwandi, ZG
    et al.
    Chalmers University of Technology and Göteborg University.
    Nour, Omer
    Chalmers University of Technology and Göteborg University.
    Willander, Magnus
    Chalmers University of Technology and Göteborg University.
    Calander, N
    Chalmers University of Technology and Göteborg University.
    dc characteristics of a nanoscale water-based transistor2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 83, no 25, p. 5310-5312Article in journal (Refereed)
    Abstract [en]

    We demonstrate a nanoscale water-based transistor. The presented nanoscale water-based transistor relies on the controlled modification of the pH in deionized water through the base applied electric field. The dc characteristics are presented and studied with a focus on the influence of the base applied electric field, the base electrode design, and their proximity to the sensing emitter and collector nanoelectrodes. The demonstrated water-based nanoscale device is of interest for many bioelectrical applications due to the biocompatibility and the wide usage and presence of water in biological systems.

  • 82.
    Chiragwandi, ZG
    et al.
    Göteborg University.
    Nour, Omer
    Göteborg University.
    Willander, Magnus
    Göteborg University.
    Panas, I
    Chalmers.
    Vortex rings in pure water under static external electric field2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 15Article in journal (Refereed)
    Abstract [en]

    The reproducible development of vortex rings in pure water under the action of a static external electric field is demonstrated. The phenomenon results from the electrochemical decomposition of water. Given the low conductivity of water in the absence of electrolyte, the field-driven buildup of hydroxide ions at the anode becomes essential to the proton release, which in turn is the result of the molecular O-2(g) evolution. Water recombination processes, which have protons flowing in a hydroxide background, as a key ingredient produce the phenomenon.

  • 83.
    Chirita, Valeriu
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Münger, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Sundgren, Jan-Erik
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Greene, Joseph E
    University of Illinois, Urbana, USA.
    Enhanced cluster mobilities on Pt(111) during film growth from the vapor phase1998In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 72, no 1, p. 127-129Article in journal (Refereed)
    Abstract [en]

    We use molecular dynamics simulations to follow the dynamics of small two-dimensional Pt clusters on Pt(111) at 1000 K. While close-packed Pt-7 heptamers are extremely stable structures, the addition of a single cluster vacancy or an on-top adatom immediately results in intracluster bond breaking, reconfigurations, rotations, the introduction of stacking faults, and greatly enhanced cluster diffusion rates. Mapping center-of-mass motion for total simulation times >145 ns revealed increases in cluster velocities by more than an order of magnitude with cluster migration occurring primarily by concerted motion and a novel diffusion mechanism involving double shearing of dimers/trimers. Contrary to some previous reports, edge-atom diffusion plays only a minor role. (C) 1998 American Institute of Physics.

  • 84.
    Chr Germs, W.
    et al.
    Eindhoven University of Technology, Netherlands.
    Roeling, E. M.
    Eindhoven University of Technology, Netherlands.
    van IJzendoorn, L. J.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Diffusion enhancement in on/off ratchets2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 7, article id 073104Article in journal (Refereed)
    Abstract [en]

    We show a diffusion enhancement of suspended polystyrene particles in an electrical on/off ratchet. The enhancement can be described by a simple master equation model. Furthermore, we find that the diffusion enhancement can be described by a general curve whose shape is only determined by the asymmetry of the ratchet repeat unit. The scaling of this curve can be explained from an analytical expression valid for small off-times. Finally, we demonstrate how the master equation model can be used to find the driving parameters for optimal particle separation. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4793198]

  • 85.
    Christova, C. G.
    et al.
    Eindhoven University of Technology, Netherlands.
    Stouwdam, J. W.
    Eindhoven University of Technology, Netherlands.
    Eijkemans, T. J.
    Eindhoven University of Technology, Netherlands.
    Silov, A. Yu.
    Eindhoven University of Technology, Netherlands.
    van der Heijden, R. W.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Janssen, R. A. J.
    Eindhoven University of Technology, Netherlands; Eindhoven University of Technology, Netherlands.
    Salemink, H. W. M.
    Delft University of Technology, Netherlands.
    Photoluminescence enhancement in thin films of PbSe nanocrystals2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 12, article id 121906Article in journal (Refereed)
    Abstract [en]

    Remarkable photoluminescence enhancement (PLE) in submonolayer films of PbSe nanocrystals (NCs) upon continuous illumination was observed. The intensity increase from films on InP substrates was highest in vacuum, while for films on Si/SiO(2) substrates the PLE was stronger in air. The magnitude of the PLE was found to depend on the excitation intensity, being higher for a weaker irradiation power. The possible mechanisms behind the phenomenon of the PLE are discussed and it is suggested to originate mainly from charge trapping outside the NCs core. (C) 2008 American Institute of Physics.

  • 86.
    Coletti, C.
    et al.
    University of South Florida, Tampa, USA.
    Frewin, C. L.
    University of South Florida, Tampa, USA.
    Saddow, S. E.
    University of South Florida, Tampa, USA.
    Hetzel, M.
    Virojanadara, Chariya
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Starke, Ulrich
    Max-Planck-Institut für Festkörperforschung, Stuttgart, Germany.
    Surface studies of hydrogen etched 3C-SiC(001) on Si(001)2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 6, p. 061914-Article in journal (Refereed)
    Abstract [en]

    Themorphology and structure of 3C-SiC(001) surfaces, grown on Si(001) andprepared via hydrogen etching, are studied using atomic force microscopy(AFM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES).On the etched samples, flat surfaces with large terraces andatomic steps are revealed by AFM. In ultrahigh vacuum asharp LEED pattern with an approximate (5×1) periodicity is observed. AES studies reveal a “bulklike” composition up to the nearsurface region and indicate that an overlayer consisting of aweakly bound silicon oxide monolayer is present.

  • 87.
    Crispin, Annica
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Berggren, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Transition between energy level alignment regimes at a low band gap polymer-electrode interfaces2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 89, no 21Article in journal (Refereed)
    Abstract [en]

    The energy level alignment at interfaces between a low band gap conjugated polymer and various electrodes is investigated using ultraviolet photoemission spectroscopy. When the electrode work function is lower (higher) than the negative (positive) polaronic level of the polymer, the Fermi level is pinned to the negative (positive) polaronic level. These Fermi level pinning regimes suggest a spontaneous electron transfer from or towards the electrode resulting in an interfacial dipole of different orientation. On the contrary, when the substrate work function is intermediate, there is no charge transfer and the energy level alignment across the interface follows the Schottky-Mott limit. © 2006 American Institute of Physics.

  • 88. Czigany, Zs.
    et al.
    Brunell, I.F.
    Neidhardt, Jörg
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Suenaga, K.
    JST, c/o Meijo University, 468-8502 Nagoya, Japan.
    Growth of fullerene-like carbon nitride thin solid films consisting of cross-linked nano-onions2001In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 79, no 16, p. 2639-2641Article in journal (Refereed)
    Abstract [en]

    Fullerene-like CNx (x˜0.12) thin solid films were deposited by reactive magnetron sputtering of graphite in a nitrogen and argon discharge on cleaved NaCl and Si(001) substrates at 450°C. As-deposited films consist of 5 nm diam CNx nano-onions with shell sizes corresponding to Goldberg polyhedra determined by high-resolution transmission electron microscopy. Electron energy loss spectroscopy revealed that N incorporation is higher in the core of the onions than at the perimeter. N incorporation promotes pentagon formation and provides reactive sites for interlinks between shells of the onions. A model is proposed for the formation of CNx nano-onions by continuous surface nucleation and growth of hemispherical shells. © 2001 American Institute of Physics.

  • 89.
    Dagnelund, Daniel
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Buyanova, Irina
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Mchedlidze, T.
    Chen, Weimin
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Utsumi, A.
    Furukawa, Y.
    Moon, S.
    Wakahara, A.
    Yonezu, H.
    Effect of nitrogen ion bombardment on defect formation and luminescence efficiency of GaNP epilayers grown by molecular-beam epitaxy2006In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 88, no 10, p. 101904-Article in journal (Refereed)
    Abstract [en]

    Radiative efficiency of GaNP epilayers grown on GaP substrates by solid-source molecular beam epitaxy is significantly improved by reduced nitrogen ion bombardment during the growth. Based on the results of temperature-dependent photoluminescence (PL) and optically detected magnetic resonance studies (ODMR), the observed improvements are attributed to reduced formation of defects, such as a Ga interstitial related defect and an unidentified defect revealed by ODMR. We demonstrate that these defects act as competing recombination centers, which promote thermal quenching of the PL intensity and result in a substantial (34×) decrease in room-temperature PL intensity. © 2006 American Institute of Physics.

  • 90.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Puustinen, J.
    Tampere University of Technology, Finland .
    Guina, M.
    Tampere University of Technology, Finland .
    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.
    Identification of an isolated arsenic antisite defect in GaAsBi2014In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 104, no 5, p. 052110-Article in journal (Refereed)
    Abstract [en]

    Optically detected magnetic resonance and photoluminescence spectroscopy are employed to study grown-in defects in GaAs0.985Bi0.015 epilayers grown by molecular beam epitaxy. The dominant paramagnetic defect is identified as an isolated arsenic antisite, As-Ga, with an electron g-factor of 2.03 +/- 0.01 and an isotropic hyperfine interaction constant A (900 +/- 620) x 10(-4) cm(-1). The defect is found to be preferably incorporated during the growth at the lowest growth temperature of 270 degrees C, but its formation can be suppressed upon increasing growth temperature to 315 degrees C. The As-Ga concentration is also reduced after post-growth rapid thermal annealing at 600 degrees C.

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  • 91.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Ren, Q. J.
    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.
    Murayama, A.
    Graduate School of Information Science and Technology, Hokkaido University, Japan.
    Antiferromagnetic coupling in CdSe/ZnMnSe quantum dot structures2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 101, no 5, p. 052405-1-052405-Article in journal (Refereed)
    Abstract [en]

    Spin polarization of nonmagnetic CdSe quantum dots (QDs) coupled to adjacent ZnMnSe diluted magnetic semiconductor (DMS) is investigated by CW and time-resolved magneto-optical spectroscopy under tunable laser excitation. Efficient enhancement in the degree of σ circular polarization of photoluminescence from the CdSe QDs is observed under optical excitation at the σ+-active exciton state of the DMS. The fact that the enhancement persists much longer than the exciton lifetime of the DMS rules out a role of the DMS excitons. A possible explanation is discussed in terms of antiferromagnetic coupling between the excitons in QDs and aligned Mn ions in DMS.

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  • 92.
    Dagnelund, Daniel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Stehr, Jan E.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Yu Egorov, A
    St Petersburg Academic University, Russia .
    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.
    Optically detected magnetic resonance studies of point defects in quaternary GaNAsP epilayers grown by vapor phase epitaxy2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 2, p. 021910-Article in journal (Refereed)
    Abstract [en]

    Defect properties of quaternary GaNAsP/GaP epilayers grown by vapor phase epitaxy (VPE) are studied by photoluminescence and optically detected magnetic resonance techniques. Incorporation of more than 0.6% of nitrogen is found to facilitate formation of several paramagnetic defects which act as competing carrier recombination centers. One of the defects (labeled as Ga-i-D) is identified as a complex defect that has a Ga interstitial (Ga-i) atom residing inside a Ga tetrahedron as its core. A comparison of Ga-i-D with other Ga-i-related defects known in ternary GaNP and GaNAs alloys suggests that this defect configuration is specific to VPE-grown dilute nitrides.

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  • 93.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Boosalis, A.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Zakharov, A. A.
    Lund University, Maxlab, Lund, Sweden.
    Hofmann, T.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Schubert, M.
    Department of Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, USA.
    Tiwald, T. E.
    J. A. Woollam Co., Lincoln, Nebraska, USA.
    Iakimov, Tihomir
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Vasiliauskas, Remigijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Yakimova, Rositsa
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Large-area microfocal spectroscopic ellipsometry mapping of thickness and electronic properties of epitaxial graphene on Si- and C-face of 3C-SiC(111)2013In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 102, no 21, p. 213116-Article in journal (Refereed)
    Abstract [en]

    Microfocal spectroscopic ellipsometry mapping of the electronic properties and thickness of epitaxial graphene grown by high-temperature sublimation on 3C-SiC (111) substrates is reported. Growth of one monolayer graphene is demonstrated on both Si- and C-polarity of the 3C-SiC substrates and it is shown that large area homogeneous single monolayer graphene can be achieved on the Si-face substrates. Correlations between the number of graphene monolayers on one hand and the main transition associated with an exciton enhanced van Hove singularity at ∼4.5 eV and the free-charge carrier scattering time, on the other are established. It is shown that the interface structure on the Si- and C-polarity of the 3C-SiC(111) differs and has a determining role for the thickness and electronic properties homogeneity of the epitaxial graphene.

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  • 94.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . Linköping University, The Institute of Technology.
    Hofmann, T
    University of Nebraska.
    Schubert, M
    University of Nebraska.
    Sernelius, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Materials Science . 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.
    Giuliani, Finn
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Alves, E
    Sacavem, Portugal.
    Lu, H
    Cornell University.
    Schaff, W J
    Cornell University.
    Free electron behavior in InN: On the role of dislocations and surface electron accumulation2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 2, p. 022109-Article in journal (Refereed)
    Abstract [en]

    The free electron behavior in InN is studied on the basis of decoupled bulk and surface accumulation electron densities in InN films measured by contactless optical Hall effect. It is shown that the variation in the bulk electron density with film thickness does not follow the models of free electrons generated by dislocation-associated nitrogen vacancies. This finding, further supported by transmission electron microscopy results, indicates the existence of a different thickness-dependent doping mechanism. Furthermore, we observe a noticeable dependence of the surface electron density on the bulk density, which can be exploited for tuning the surface charge in future InN based devices.

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  • 95.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials.
    Usui, A.
    On the lattice parameters of GaN2007In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 3, p. 031911-Article in journal (Refereed)
    Abstract [en]

    The lattice parameters of low-defect density, undoped bulk GaN fabricated by hydride vapor phase epitaxy (HVPE) on (0001) sapphire and subsequent substrate removal, are precisely determined using high-resolution x-ray diffraction. The obtained values, c=5.18523 Å and a=3.18926 Å, are compared with the lattice parameters of freestanding HVPE GaN from different sources and found to be representative for state-of-the-art undoped HVPE bulk GaN material. A comparison with bulk GaN fabricated by the high-pressure technique and homoepitaxial GaN is made, and significant differences in the lattice parameters are found. The observed differences are discussed and a possible explanation is suggested. © 2007 American Institute of Physics.

  • 96.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Birch, Jens
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Tungasmita, Sukkaneste
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Deformation potentials of the E-1(TO) mode in AlN2002In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 80, no 13, p. 2302-2304Article in journal (Refereed)
    Abstract [en]

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

  • 97.
    Darakchieva, Vanya
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskov, Plamen
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Paskova, Tanja
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Valcheva, E.
    Monemar, Bo
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Materials Science .
    Heuken, M.
    Aixtron AG, D-52072 Aachen, Germany.
    Lattice parameters of GaN layers grown on a-plane sapphire: Effect of in-plane strain anisotropy2003In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 82, no 5, p. 703-705Article in journal (Refereed)
    Abstract [en]

    The lattice parameters of GaN layers grown on a-plane sapphire were investigated. The hydride vapor phase epitaxy and metalorganic vapor phase epitaxy were used for the determination of parameters. The strain anisotropy was found to have different values in the films and obtained values of parameters were grouped around two values.

  • 98.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology.
    Paskov, Plamen
    Linköping University, Department of Physics, Chemistry and Biology.
    Valcheva, E
    Paskova, Tanja
    Linköping University, Department of Physics, Chemistry and Biology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology.
    Schubert, M
    Lu, H
    Schaff, W.J.
    Deformation potentials of the E1 (TO) and E2 modes of InN2004In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 84, no 18, p. 3636-3638Article in journal (Refereed)
    Abstract [en]

    The determination of deformation potentials of E1(TO) and E 2 modes of InN were discussed. The deformation potentials were evaluated for two sets of stiffness constants using x-ray diffraction, IR spectroscopic ellipsometry (IRSE), Raman scattering, and Grüneisen parameter values. The InN layer were grown on GaN buffer layers on (0001) sapphire by molecular beam epitaxy. It was found that the strain-free values of the InN E1(TO) mode was 477.9 cm-1 and 491.9 cm -1 for the E2 modes.

  • 99.
    Darakchieva, Vanya
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Xie, Mengyao
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Tasnadi, Ferenc
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Hultman, Lars
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Monemar, Bo
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
    Kamimura, J
    Sophia University.
    Kishino, K
    Japan Science & Technology Agency.
    Lattice parameters, deviations from Vegards rule, and E-2 phonons in InAlN2008In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 93, no 26, p. 261908-Article in journal (Refereed)
    Abstract [en]

    The lattice parameters of InxAl1-xN in the whole compositional range are studied using first-principle calculations. Deviations from Vegards rule are obtained via the bowing parameters, delta(a)=0.0412 +/- 0.0039 A and delta(c)=-0.060 +/- 0.010 A, which largely differ from previously reported values. Implications of the observed deviations from Vegards rule on the In content extracted from x-ray diffraction are discussed. We also combine these results with x-ray diffraction and Raman scattering studies on InxAl1-xN nanocolumns with 0.627 <= x <= 1 and determine the E-2 phonon frequencies versus In composition in the scarcely studied In-rich compositional range.

  • 100.
    Davidsson, Joel
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ivády, Viktor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Hungarian Acad Sci, Hungary.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Ohshima, Takeshi
    Natl Inst Quantum and Radiol Sci and Technol, Japan.
    Nguyen, Son Tien
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Gali, Adam
    Hungarian Acad Sci, Hungary; Budapest Univ Technol and Econ, Hungary.
    Abrikosov, Igor
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering. Natl Univ Sci and Technol MISIS, Russia.
    Identification of divacancy and silicon vacancy qubits in 6H-SiC2019In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 114, no 11, article id 112107Article in journal (Refereed)
    Abstract [en]

    Point defects in semiconductors are relevant for use in quantum technologies as room temperature qubits and single photon emitters. Among suggested defects for these applications are the negatively charged silicon vacancy and the neutral divacancy in SiC. The possible nonequivalent configurations of these defects have been identified in 4H-SiC, but for 6H-SiC, the work is still in progress. In this paper, we identify the different configurations of the silicon vacancy and the divacancy defects to each of the V1-V3 and the QL1-QL6 color centers in 6H-SiC, respectively. We accomplish this by comparing the results from ab initio calculations with experimental measurements for the zero-phonon line, hyperfine tensor, and zero-field splitting. Published under license by AIP Publishing.

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