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  • 1.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Balagula, Roman
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Yukimune, M
    Ehime University, Matsuyama, Japan.
    Fujiwara, R
    Ehime University, Matsuyama, Japan.
    Ishikawa, Fumitaro
    Ehime University, Matsuyama, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Effects of growth temperature and thermal annealing on optical quality of GaNAs nanowires emitting in the near-infrared spectral range2020In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 31, no 6, article id 065702Article in journal (Refereed)
    Abstract [en]

    We report on optimization of growth conditions of GaAs/GaNAs/GaAs core/shell/shell nanowire (NW) structures emitting at ~1 μm, aiming to increase their light emitting efficiency. A slight change in growth temperature is found to critically affect optical quality of the active GaNAs shell and is shown to result from suppressed formation of non-radiative recombination (NRR) centers under the optimum growth temperature. By employing the optically detected magnetic resonance spectroscopy, we identify gallium vacancies and gallium interstitials as being among the dominant NRR defects. The radiative efficiency of the NWs can be further improved by post-growth annealing at 680 °C, which removes the gallium interstitials.

  • 2.
    Zhang, Bin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Chinese Academy of Sciences, Shanghai, China.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, P.P.
    Chinese Academy of Sciences, Shanghai, China.
    Wang, X. J.
    Chinese Academy of Sciences, Shanghai, China.
    Lu, W
    Chinese Academy of Sciences, Shanghai, China.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Band structure of wurtzite GaBiAs nanowires2019In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 19, p. 6454-6460Article in journal (Refereed)
    Abstract [en]

    We report on the first successful growth of wurtzite (WZ) GaBiAs nanowires (NWs) and reveal the effects of Bi incorporation on the electronic band structure by using polarization-resolved optical spectroscopies performed on individual NWs. Experimental evidence of a decrease in the band-gap energy and an upward shift of the topmost three valence subbands upon the incorporation of Bi atoms is provided, whereas the symmetry and ordering of the valence band states remain unchanged, that is, Γ9, Γ7, and Γ7 within the current range of Bi compositions. The extraordinary valence band structure of WZ GaBiAs NWs is explained by anisotropic hybridization and anticrossing between p-like Bi states and the extended valence band states of host WZ GaAs. Moreover, the incorporation of Bi into GaAs is found to significantly reduce the temperature sensitivity of the band-gap energy in WZ GaBiAs NWs. Our work therefore demonstrates that utilizing dilute bismide alloys provides new avenues for band-gap engineering and thus photonic engineering with NWs.

    The full text will be freely available from 2020-08-19 15:11
  • 3.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Cai, Li
    International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, 710049, Shaanxi, China.
    Shen, Shaohua
    International Research Center for Renewable Energy, State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, 710049, Shaanxi, China.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Effects of N implantation on defect formation in ZnO nanowires2019In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 687, article id UNSP 137449Article in journal (Refereed)
    Abstract [en]

    One-dimensional ZnO nanowires are a promising material system for a wide range of optoelectronic and photonic applications. Utilization of ZnO, however, requires high-quality ZnO with reliable n-type and p-type conductivity, with the latter remaining elusive, so far. In this work we report on effects of N doping via ion implantation on defect formation in ZnO nanowires studied by optically detected paramagnetic resonance (ODMR) spectroscopy complemented by photoluminescence spectroscopy. After N implantation, zinc interstitial shallow donors, which are formed as a result of ion implantation, are observed in addition to effective mass type shallow donors. Additionally, ODMR signals related to oxygen vacancies can be observed. Implantation also causes formation of a new nitrogen related defect center, which acts as an acceptor. The present findings are of importance for understanding impacts of different defects and impurities on electronic properties of nanostructured ZnO and achieving p-type conductivity via nitrogen doping.

    The full text will be freely available from 2021-08-01 08:00
  • 4.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Hofmann, Detlev
    Justus-Liebig-University Giessen, Giessen, Germany.
    Schörmann, Jörg
    Justus-Liebig-University Giessen, Giessen, Germany.
    Becker, Martin
    Justus-Liebig-University Giessen, Giessen, Germany.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Electron paramagnetic resonance signatures of Co2+ and Cu2+ in β-Ga2O32019In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 115, no 24, article id 242101Article in journal (Refereed)
    Abstract [en]

    Gallium oxide (β-Ga2O3) is a wide-bandgap compound semiconductor with a bandgap of ∼4.9 eV that is currently considered promising for a wide range of applications ranging from transparent conducting electrodes to UV optoelectronic devices and power electronics. However, all of these applications require a reliable and precise control of electrical and optical properties of the material, which can be largely affected by impurities, such as transition metals commonly present during the growth. In this work, we employ electron paramagnetic resonance (EPR) spectroscopy to obtain EPR signatures of the 3d-transition metals Co2+ and Cu2+ in β-Ga2O3 bulk crystals and powders that were unknown so far. Furthermore, we show that both Co2+ and Cu2+ preferentially reside on the octahedral gallium lattice site.

  • 5.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Pearton, Stephen
    Uecker, Reinhard
    Hofmann, Detlev
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Electron paramagnetic resonance signatures of defects and impurities in β-Ga2O32019Conference paper (Refereed)
  • 6.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Sensor and Actuator Systems. Linköping University, Faculty of Science & Engineering.
    Karlsson, Jan Olof G.
    Linköping University, Department of Medical and Health Sciences, Division of Drug Research. Linköping University, Faculty of Medicine and Health Sciences.
    Evidence that fodipir (DPDP) binds neurotoxic Pt2+ with a high affinity: An electron paramagnetic resonance study2019In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 15813Article in journal (Refereed)
    Abstract [en]

    Oxaliplatin typically causes acute neuropathic problems, which may, in a dose-dependent manner, develop into a chronic form of chemotherapy-induced peripheral neuropathy (CIPN), which is associated with retention of Pt2+ in the dorsal root ganglion. A clinical study by Coriat and co-workers suggests that co-treatment with mangafodipir [Manganese(II) DiPyridoxyl DiPhosphate; MnDPDP] cures ongoing CIPN. These authors anticipated that it is the manganese superoxide dismutase mimetic activity of MnDPDP that explains its curative activity. However, this is questionable from a pharmacokinetic perspective. Another, but until recently undisclosed possibility is that Pt2+ outcompetes Mn2+/Ca2+/Zn2+ for binding to DPDP or its dephosphorylated metabolite PLED (diPyridoxyL EthylDiamine) and transforms toxic Pt2+ into a non-toxic complex, which can be readily excreted from the body. We have used electron paramagnetic resonance guided competition experiments between MnDPDP (10logKML ≈ 15) and K2PtCl4, and between MnDPDP and ZnCl2 (10logKML ≈ 19), respectively, in order to obtain an estimate the 10logKML of PtDPDP. Optical absorption spectroscopy revealed a unique absorption line at 255 nm for PtDPDP. The experimental data suggest that PtDPDP has a higher formation constant than that of ZnDPDP, i.e., higher than 19. The present results suggest that DPDP/PLED has a high enough affinity for Pt2+ acting as an efficacious drug in chronic Pt2+-associated CIPN.

  • 7.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Cai, Li
    Xi An Jiao Tong Univ, Peoples R China.
    Shen, Shaohua
    Xi An Jiao Tong Univ, Peoples R China.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Identification of a Nitrogen-related acceptor in ZnO nanowires2019In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 11, no 22, p. 10921-10926Article in journal (Refereed)
    Abstract [en]

    Nanostructured ZnO, such as ZnO nanowires (NWs), is a promising material system for a wide range of electronic applications ranging from light emission to water splitting. Utilization of ZnO requires development of effective and controllable p-type doping. Nitrogen is considered among key p-type dopants though the exact origin of N-induced acceptors is not fully understood, especially in the case of nanostructured ZnO. In this work we employ electron paramagnetic resonance (EPR) spectroscopy to characterize N-related acceptors in ZnO NWs. N doping was achieved using ion implantation commonly employed for these purposes. We show that the Fermi level position is lowered in the N implanted NWs, indicating the formation of compensating acceptors. The formed acceptor is unambiguously proven to involve an N atom based on a resolved hyperfine interaction with a 14N nucleus with a nuclear spin I = 1. The revealed center is shown to act as a deep acceptor with an energy level located at about 1.1 eV above the top of the valence band. This work represents the first unambiguous identification of acceptors deliberately introduced in ZnO nanostructures. It also shows that the configuration and electronic structure of the N-related acceptors in nanostructures differ from those in ZnO bulk and thin-films. The present findings are of importance for understanding the electronic properties of nanostructured ZnO required for its future electronic applications.

  • 8.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Cai, Li
    Xi'an Jiaotong University, Shaanxi, China.
    Shen, Shaohua
    Xi'an Jiaotong University, Shaanxi, China.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Identification of a N-related acceptor in ZnO nanowires2019Conference paper (Refereed)
  • 9.
    Jansson, Mattias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Francaviglia, Luca
    Ecole Polytech Fed Lausanne, Switzerland.
    La, Rui
    Univ Calif San Diego, CA 92093 USA.
    Balagula, Roman
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Tu, Charles W.
    Univ Calif San Diego, CA 92093 USA.
    Morral, Anna Fontcuberta I
    Ecole Polytech Fed Lausanne, Switzerland; Ecole Polytech Fed Lausanne, Switzerland.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Increasing N content in GaNAsP nanowires suppresses the impact of polytypism on luminescence2019In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 30, no 40, article id 405703Article in journal (Refereed)
    Abstract [en]

    Cathodoluminescence (CL) and micro-photoluminescence spectroscopies are employed to investigate effects of structural defects on carrier recombination in GaNAsP nanowires (NWs) grown by molecular beam epitaxy on Si substrates. In the NWs with a low N content of 0.08%, these defects are found to promote non-radiative (NR) recombination, which causes spatial variation of the CL peak position and its intensity. Unexpectedly, these detrimental effects can be suppressed even by a small increase in the nitrogen composition from 0.08% to 0.12%. This is attributed to more efficient trapping of excited carriers/excitons to the localized states promoted by N-induced localization and also the presence of other NR channels At room temperature, the structural defects no longer dominate in carrier recombination even in the NWs with the lower nitrogen content, likely due to increasing importance of other recombination channels. Our work underlines the need in eliminating important thermally activated NR defects, other than the structural defects, for future optoelectronic applications of these NWs.

  • 10.
    Rudko, G.Yu
    et al.
    V. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Vorona, I. P.
    V. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Dzhagan, V. M.
    V. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Raevskaya, A. E.
    L. Pysarzhevsky Institute of Physical Chemistry, National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Stroyuk, O. L.
    L. Pysarzhevsky Institute of Physical Chemistry, National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Fediv, V. I.
    Bukovinian State Medical University, Chernivtsi, Ukraine.
    Kovalchuk, A. O.
    V. Lashkaryov Institute of Semiconductor Physics of National Academy of Sciences of Ukraine, prospect Nauky, Kyiv, Ukraine.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Optically detected magnetic resonance study of relaxation/emission processes in the nanoparticle-polymer composite2019In: SPQEO, ISSN 1605-6582, Vol. 22, no 3, p. 310-318Article in journal (Refereed)
    Abstract [en]

    Two nanocomposites containing CdS nanoparticles in polymeric matrices were studied using the photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. Due to equal sizes of NPs in the composites (~5 nm) but different matrices – the oxygen-containing polymer PVA (polyvinyl alcohol) and oxygen-free polymer PEI (polyethyleneimine) – differences of nanocomposites properties are predominantly caused by different interfacial conditions. ODMR spectra have revealed five types of centers related to the PL emission – four centers involved in radiative recombination and one center related to non-radiative recombination processes. The oxygen-related interfacial center in CdS/PVA (LK1-center) and sulfur vacancy center in CdS/PEI (Vs-center) were identified.

  • 11.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Shen, Shaohua
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Effects of N implantation on defect formation in ZnO nanowires2018Conference paper (Refereed)
  • 12.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Svensson, B. G.
    Univ Oslo, Norway.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Efficient Auger Charge-Transfer Processes in ZnO2018In: Physical Review Applied, ISSN 2331-7019, Vol. 9, no 5, article id 054014Article in journal (Refereed)
    Abstract [en]

    Photoluminescence and magneto-optical measurements are performed on a line peaking at 3.354 eV (labeled as NBX) in electron-irradiated ZnO. Even though the energy position of the NBX line is close to that for bound excitons in ZnO, it has distinctively different magneto-optical properties. Photoelectron paramagnetic resonance measurements reveal a connection and a charge-transfer process involving NBX and Fe and Al centers. The experimental results are explained within a model which assumes that the NBX is a neutral donor bound exciton at a defect center located near a Fe impurity and an Auger-type charge-transfer process occurs between NBX and Fe3+. While the NBX dissociates, its hole is captured by an excited state of Fe3+ and the released energy is transferred to the NBX electron, which is excited to the conduction band and subsequently trapped by a substitutional Al-zn shallow donor.

  • 13.
    Askari, Sadegh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Christian Albrechts Univ Kiel, Germany.
    Mariotti, Davide
    Ulster Univ, North Ireland.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Benedikt, Jan
    Christian Albrechts Univ Kiel, Germany.
    Keraudy, Julien
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Helmersson, Ulf
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Low-Loss and Tunable Localized Mid-Infrared Plasmons in Nanocrystals of Highly Degenerate InN2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 9, p. 5681-5687Article in journal (Refereed)
    Abstract [en]

    Plasmonic response of free charges confined in nanostructures of plasmonic materials is a powerful means for manipulating the light-material interaction at the nanoscale and hence has influence on various relevant technologies. In particular, plasmonic materials responsive in the mid-infrared range are technologically important as the mid-infrared is home to the vibrational resonance of molecules and also thermal radiation of hot objects. However, the development of the field is practically challenged with the lack of low-loss materials supporting high quality plasmons in this range of the spectrum. Here, we demonstrate that degenerately doped InN nanocrystals (NCs) support tunable and low-loss plasmon resonance spanning the entire midwave infrared range. Modulating free-carrier concentration is achieved by engineering nitrogen-vacancy defects (InN1-x, 0.017 amp;lt; x amp;lt; 0.085) in highly degenerate NCs using a nonequilibrium gas-phase growth process. Despite the significant reduction in the carrier mobility relative to intrinsic InN, the mobility in degenerate InN NCs (amp;gt;60 cm(2)/(V s)) remains considerably higher than the carrier mobility reported for other materials NCs such as doped metal oxides, chalcogenides, and noble metals. These findings demonstrate feasibility of controlled tuning of infrared plasmon resonances in a low-loss material of III-V compounds and open a gateway to further studies of these materials nanostructures for infrared plasmonic applications.

  • 14.
    Shakeri Yekta, Sepehr
    et al.
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Hedenstrom, Mattias
    Department of Chemistry, Umeå University, Umeå, Sweden.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Dario, Mårten
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Hertkorn, Norbert
    German Res Ctr Environm Hlth, Germany.
    Björn (Fredriksson), Annika
    Linköping University, Department of Thematic Studies, Tema Environmental Change. Linköping University, Faculty of Arts and Sciences.
    Pretreatment,of anaerobic digester samples by hydrochloric acid for solution-state H-1 and C-13 NMR spectroscopic characterization of organic matter2018In: Chemosphere, ISSN 0045-6535, E-ISSN 1879-1298, Vol. 199, p. 201-209Article in journal (Refereed)
    Abstract [en]

    Pretreatment of anaerobic digester samples by hydrochloric acid (HCl) resulted in removal of Fe-based mineral and coordination compounds, attenuating their interferences with solution-state nuclear magnetic resonance (NMR) spectroscopic characterization of the solid phase organic matter. Substrate (influent) and digestate (effluent) samples from two full-scale anaerobic digesters, designated CD (co-digester) and SSD (sewage sludge digester), were investigated. Pretreatment of CD samples with 0.2-2.0 mol l(-1) HCl and pretreatment of SSD samples with 1.0-3.0 mol l(-1) HCl removed 96-100% and 76-80% of total Fe, respectively. Pretreatment declined overall paramagnetic characteristics of digestate samples, manifested by 50% (CD) and 70% (SSD) decrease in electron paramagnetic resonance signal intensities. As a result, meaningful solution-state H-1,C-13 heteronuclear single quantum coherence and H-1 NMR spectra of DMSO-d(6) soluble organic matter could be acquired. Sample pretreatment with the lowest concentration of HCl resulted in alteration of C:N ratios in solid phase, likely due to removal of labile organic and inorganic C- and N-containing compounds, while elevating the HCl concentration did not further change the C:N ratios. Furthermore, sample pretreatment increased the solubility of carbohydrates and proteins in DMSO-d(6), enabling the detection of NMR resonances from certain structural units of carbohydrates (e.g. anomeric O2CH) and proteins (e.g. CH alpha in amino acids). Both attenuation of the paramagnetic matrix as well as art enhanced solubility of carbohydrate and protein fractions of the samples in DMSO-d(6) solvent contributed to an improved molecular characterization of anaerobic digester samples by solution-state NMR analysis.

  • 15.
    Chen, Shula
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Huang, Yuqing
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ishikawa, Fumitaro
    Ehime University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Dilute Nitride Nanowire Lasers Based on a GaAs/GaNAs Core/Shell Structure2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 3, p. 1775-1781Article in journal (Refereed)
    Abstract [en]

    Nanowire (NW) lasers operating in the near infrared spectral range are of significant technological importance for applications in telecommunications, sensing, and medical diagnostics. So far, lasing within this spectral range has been achieved using GaAs/AlGaAs, GaAs/GaAsP, and InGaAs/GaAs core/shell NWs. Another promising III-V material, not yet explored in its lasing capacity, is the dilute nitride GaNAs. In this work, we demonstrate, for the first time, optically pumped lasing from the GaNAs shell of a single GaAs/GaNAs core/shell NW. The characteristic "S"-shaped pump power dependence of the lasing intensity, with the concomitant line width narrowing, is observed, which yields a threshold gain, g(th), of 3300 cm(-1) and a spontaneous emission coupling factor beta, of 0.045. The dominant lasing peak is identified to arise from the HE21b, cavity mode, as determined from its pronounced emission polarization along the NW axis combined with theoretical calculations of lasing threshold for guided modes inside the nanowire. Even without intentional pas sivation of the NW surface, the lasing emission can be sustained up to 150 K. This is facilitated by the improved surface quality due to nitrogen incorporation, which partly suppresses the surface-related nonradiative recombination centers via nitridation. Our work therefore represents the first step toward development of room-temperature infrared NW lasers based on dilute nitrides with extended tunability in the lasing wavelength.

  • 16.
    Jansson, Mattias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    La, Rui
    University of Calif San Diego, CA 92093 USA.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Tu, Charles W.
    University of Calif San Diego, CA 92093 USA; University of Calif San Diego, CA 92093 USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Effects of Nitrogen Incorporation on Structural and Optical Properties of GaNAsP Nanowires2017In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 12, p. 7047-7055Article in journal (Refereed)
    Abstract [en]

    In this work, we carry out a comprehensive investigation of structural and optical effects in GaNAsP nanowires (NWs), which are novel materials promising for advanced photovoltaic applications. Despite a significant mismatch in electronegativity between N and As/P atoms, we show that incorporation of nitrogen does not degrade structural quality of the nanowires and the fabricated NW arrays have excellent compositional uniformity among individual wires. From temperature-dependent photoluminescence (PL) measurements, statistical fluctuations of the alloy composition are shown to lead to localization of photoexcited carriers at low temperatures but do not affect material properties at room temperature. According to time-resolved PL measurements, the room-temperature carrier lifetime increases in the GaNAsP NWs as compared with the GaAsP NWs, which indicates reduced nonradiative recombination. Moreover, in spite of the very low N content in the studied NWs (up to 0.16%), their bandgap energy can be tuned by more than 100 meV. This is accompanied by about 30% reduction in the temperature dependence of the bandgap energy. The presented results demonstrate that alloying of GaAsP with nitrogen provides an additional means of design optimization, beneficial for, e.g., NW-based intermediate band solar cells that are highly dependent on the optimum bandgap structure.

  • 17.
    Rudko, Galyna Yu.
    et al.
    National Academic Science Ukraine, Ukraine.
    Vorona, Igor P.
    National Academic Science Ukraine, Ukraine.
    Fediv, Volodymyr I.
    Bukovinian State Medical University, Ukraine.
    Kovalchuk, Andrii
    National Academic Science Ukraine, Ukraine.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Shanina, Bela D.
    National Academic Science Ukraine, Ukraine.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Luminescent and Optically Detected Magnetic Resonance Studies of CdS/PVA Nanocomposite2017In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 12, article id 130Article in journal (Refereed)
    Abstract [en]

    A series of solid nanocomposites containing CdS nanoparticles in polymeric matrix with varied conditions on the interface particle/polymer was fabricated and studied by photoluminescence (PL) and optically detected magnetic resonance (ODMR) methods. The results revealed interface-related features in both PL and ODMR spectra. The revealed paramagnetic centers are concluded to be involved in the processes of photo-excited carriers relaxation.

  • 18.
    Karimi, Mohammad
    et al.
    Lund University, Sweden; Halmstad University, Sweden.
    Jain, Vishal
    Lund University, Sweden; Halmstad University, Sweden.
    Heurlin, Magnus
    Lund University, Sweden.
    Nowzari, Ali
    Lund University, Sweden.
    Hussain, Laiq
    Lund University, Sweden; Halmstad University, Sweden.
    Lindgren, David
    Lund University, Sweden.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Gustafsson, Anders
    Lund University, Sweden.
    Samuelson, Lars
    Lund University, Sweden.
    Borgström, Magnus T.
    Lund University, Sweden.
    Pettersson, Håkan
    Lund University, Sweden; Halmstad University, Sweden.
    Room-temperature InP/InAsP Quantum Discs-in-Nanowire Infrared Photodetectors2017In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 6, p. 3356-3362Article in journal (Refereed)
    Abstract [en]

    The possibility to engineer nanowire heterostructures with large bandgap variations is particularly interesting for technologically important broadband photodetector applications. Here we report on a combined study of design, fabrication, and optoelectronic properties of infrared photodetectors comprising four million n(+)in(+) InP nanowires periodically ordered in arrays. The nanowires were grown by metalorganic vapor phase epitaxy on InP substrates, with either a single or 20 InAsP quantum discs embedded in the i-segment. By Zn compensation of the residual n-dopants in the i-segment, the room-temperature dark current is strongly suppressed to a level of pA/NW at 1 V bias. The low dark current is manifested in the spectrally resolved photocurrent measurements, which reveal strong photocurrent contributions from the InAsP quantum discs at room temperature with a threshold wavelength of about 2.0 m and a bias-tunable responsivity reaching 7 A/W@1.38 m at 2 V bias. Two different processing schemes were implemented to study the effects of radial self-gating in the nanowires induced by the nanowire/SiOx/ITO wrap-gate geometry. Summarized, our results show that properly designed axial InP/InAsP nanowire heterostructures are promising candidates for broadband photodetectors.

  • 19.
    Philipps, Jan M.
    et al.
    Justus Liebig University of Giessen, Germany.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Hofmann, Detlev M.
    Justus Liebig University of Giessen, Germany.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Eickhoff, Martin
    University of Bremen, Germany.
    Study of the carrier transfer across the GaNP nanowire electrolyte interface by electron paramagnetic spin trapping2017In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 110, no 22, article id 222101Article in journal (Refereed)
    Abstract [en]

    We investigate the transfer of photoexcited charge carriers from GaP and GaNP nanowires to an electrolyte by bias-dependent photocurrent and electron paramagnetic resonance experiments using 5,5-dimethyl-1-pyrroline-N-oxide as a spin trap. The results of the latter show that hydroxyl radicals are created over the entire applied bias range from -1000mV to +1300mV by hole transfer. In contrast, the photocurrent changes from cathodic to anodic at the open circuit potential of the three-electrode setup with the nanowire sample acting as the working electrode. The experiments show that the photoelectrochemical response of GaNP nanowires is significantly stronger compared to that of the GaP nanowires. Published by AIP Publishing.

  • 20.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Dobrovolsky, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Kuang, K. J.
    Sukrittanon, Supanee
    Tu, Charles W.
    Department of Electrical and Computer Engineering, University of California.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Thematic Studies. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Department of Thematic Studies. Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Defect formation and optical properties of coaxial GaP/GaNP core/shell Nanowires (invited talk)2016Conference paper (Refereed)
  • 21.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Ishikawa, F.
    Ehime University, Japan.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Defect formation in GaAs/GaNxAs1-x core/shell nanowires2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 109, no 20, article id 203103Article in journal (Refereed)
    Abstract [en]

    Photoluminescence and optically detected magnetic resonance (ODMR) spectroscopies are used to investigate the formation and role of defects in GaAs/GaNxAs1-x core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates. Gallium vacancies, which act as non-radiative recombination (NRR) centers, are identified by ODMR. It is shown that the defects are formed in bulk regions, i.e., not on the surface, of the GaNAs shell and that their concentration increases with increasing nitrogen content. Temperature dependent photoluminescence experiments reveal, on the other hand, suppressed thermal quenching of the near-band-edge emission with increasing [N]. This leads to the conclusion that the dominant NRR processes in the studied NWs are governed by surface defects, whereas the role of gallium vacancies in the observed thermally activated NRR is minor. Published by AIP Publishing.

  • 22.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Tu, C. W.
    University of Calif La Jolla, CA USA.
    Novel GaP/GaNP core/shell nanowires for optoelectronics and photonics (invited talk)2016In: The 7th IEEE International Nanoelectronics Conference 2016, IEEE , 2016Conference paper (Refereed)
    Abstract [en]

    GaNP-based nanowires (NWs) represent a novel material system that has a great potential in a variety of optoelectronic and photonic applications. In this paper we review our recent results showing that advantages provided by alloying with nitrogen can be realized and even further enhanced in novel coaxial GaNP NWs grown on Si substrates. Based on combined mu-photoluminescence and optically detected magnetic resonance measurements, we identify the optimum structural design of these nanowires. We also demonstrate that these novel structures have potential as nanoscale light sources of linearly polarized light.

  • 23.
    Filippov, Stanislav
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Jansson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Palisaitis, Justinas
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Persson, Per O. Å.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Ishikawa, Fumitaro
    Graduate School of Science and Engineering, Ehime University, Matsuyama, Japan.
    Chen, Weimin M.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Buyanova, Irina A.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Strongly polarized quantum-dot-like light emitters embedded in GaAs/GaNAs core/shell nanowires2016In: Nanoscale, ISSN 2040-3364, E-ISSN 2040-3372, Vol. 8, no 35, p. 15939-15947Article in journal (Refereed)
    Abstract [en]

    Recent developments in fabrication techniques and extensive investigations of the physical properties of III-V semiconductor nanowires (NWs), such as GaAs NWs, have demonstrated their potential for a multitude of advanced electronic and photonics applications. Alloying of GaAs with nitrogen can further enhance the performance and extend the device functionality via intentional defects and heterostructure engineering in GaNAs and GaAs/GaNAs coaxial NWs. In this work, it is shown that incorporation of nitrogen in GaAs NWs leads to formation of three-dimensional confining potentials caused by short-range fluctuations in the nitrogen composition, which are superimposed on long-range alloy disorder. The resulting localized states exhibit a quantum-dot like electronic structure, forming optically active states in the GaNAs shell. By directly correlating the structural and optical properties of individual NWs, it is also shown that formation of the localized states is efficient in pure zinc-blende wires and is further facilitated by structural polymorphism. The light emission from these localized states is found to be spectrally narrow (similar to 50-130 mu eV) and is highly polarized (up to 100%) with the preferable polarization direction orthogonal to the NW axis, suggesting a preferential orientation of the localization potential. These properties of self-assembled nano-emitters embedded in the GaNAs-based nanowire structures may be attractive for potential optoelectronic applications.

  • 24.
    Stehr, Jan Eric
    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, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Svensson, Bengt
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    The zinc vacancy – donor complex: A relevant compensating center in n-type ZnO (invited talk)2016Conference paper (Refereed)
  • 25.
    Stehr, Jan Eric
    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, Faculty of Science & Engineering.
    Svensson, B. G.
    University of Oslo, Norway.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Thermal stability of the prominent compensating (Al-Zn-V-Zn) center in ZnO2016In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 119, no 10, p. 105702-Article in journal (Refereed)
    Abstract [en]

    Electron paramagnetic resonance spectroscopy is used to investigate the thermal stability of the Aluminum-Zinc vacancy (Al-Zn-V-Zn) complex created in bulk single crystalline ZnO by room temperature electron irradiation with an energy of 1.2 MeV. Two different stages in the annealing process at 160 and 250 degrees C with apparent activation energies of E-A1 = 1.5 +/- 0.2 eV and E-A2 = 1.9 +/- 0.2 eV, respectively, are observed. The second stage leads to the complete annealing out of the (Al-Zn-V-Zn) complex and is accompanied by restoration of the concentration of the AlZn shallow donor centers to its initial value in as-grown (i.e., not irradiated) material. The obtained results prove that the (Al-Zn-V-Zn) complex is the dominant acceptor responsible for compensation of n-type-dopants in the studied Al-containing ZnO samples. (C) 2016 AIP Publishing LLC.

  • 26.
    Stehr, Jan Eric
    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, Faculty of Science & Engineering.
    Reddy, N. K.
    Humboldt University, Institute of Chemistry, Berlin, Germany .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, USA .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Unintentional nitrogen incorporation in ZnO nanowires detected by electron paramagnetic resonance spectroscopy2016In: Physica Status Solidi. C, Current topics in solid state physics, ISSN 1610-1634, E-ISSN 1610-1642, Vol. 13, no 7-9, p. 572-575Article in journal (Refereed)
    Abstract [en]

    Unintentional incorporation of nitrogen in ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition is unambiguously proven by electron paramagnetic resonance spectroscopy. The nitrogen dopants are suggested to be provided from contaminations in the source gases. The majority of incorporated nitrogen atoms are concluded to reside at oxygen sites, i.e. in the atomic configuration of nitrogen substituting for oxygen (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in a bulk material. This implies that the defect formation energy at the NW surface could be lower than its bulk value, consistent with previous theoretical predictions. The obtained results underline that nitrogen can be easily incorporated in ZnO nanostructures which may be of advantage for realizing p-type conducting ZnO via N doping. On the other hand, the awareness of this process can help to prevent such unintentional doping in structures with desired n-type conductivity.

  • 27.
    Stehr, Jan Eric
    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.
    Koteeswawa Reddy, Nandanapalli
    Humboldt University, Institute of Chemistry, Berlin, Germany.
    Tu, Charles W.
    University of California, Department of Electrical and Computer Engineering, La Jolla, CA, USA.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient nitrogen incorporation in ZnO nanowires2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 13406Article in journal (Refereed)
    Abstract [en]

    One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

  • 28.
    Stehr, Jan Eric
    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.
    Reddy, Nandanapalli Koteeswara
    Tu, C.W.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Efficient Nitrogen Incorporation in ZnO Nanowires by Unintentional Doping2015Conference paper (Refereed)
  • 29.
    Stehr, Jan Eric
    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, Faculty of Science & Engineering.
    Reddy, Nandanapalli Koteeswara
    Humboldt University, Institute of Chemistry, Berlin, 12489, Germany.
    Tu, Charles W
    University of California, Department of Electrical and Computer Engineering, La Jolla, CA 92093, USA.
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Efficient Nitrogen Incorporation in ZnO Nanowires by Unintentional Doping2015Conference paper (Refereed)
    Abstract [en]

    One-dimensional ZnO nanowires (NWs) are a promising materials system for a variety of applications. Utilization of ZnO, however, requires a good understanding and control of material properties that are largely affected by intrinsic defects and contaminants. In this work we provide experimental evidence for unintentional incorporation of nitrogen in ZnO NWs grown by rapid thermal chemical vapor deposition, from electron paramagnetic resonance spectroscopy. The incorporated nitrogen atoms are concluded to mainly reside at oxygen sites (NO). The NO centers are suggested to be located in proximity to the NW surface, based on their reduced optical ionization energy as compared with that in bulk. This implies a lower defect formation energy at the NW surface as compared with its bulk value, consistent with theoretical predictions. The revealed facilitated incorporation of nitrogen in ZnO nanostructures may be advantageous for realizing p-type conducting ZnO via N doping. The awareness of this process can also help to prevent such unintentional doping in structures with desired n-type conductivity.

  • 30.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dobrovolsky, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Sukrittanon, S.
    Kuang, Y.
    Tu, C.W.
    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.
    Fabry-Perot Microcavity Modes in Single GaP/GaNP Core/Shell Nanowires.2015Conference paper (Refereed)
  • 31.
    Dobrovolsky, Alexander
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, CA, USA.
    Kuang, Y.
    Department of Physics, University of California, La Jolla, CA, USA.
    Tu, C.W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, CA, 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.
    Fabry-Perot Microcavity Modes in Single GaP/GaNP Core/Shell Nanowires2015In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 11, no 47, p. 6331-6337Article in journal (Refereed)
    Abstract [en]

    Semiconductor nanowires (NWs) are attracting increasing interest as nanobuilding blocks for optoelectronics and photonics. A novel material system that is highly suitable for these applications are GaNP NWs. In this article, we show that individual GaP/GaNP core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates can act as Fabry-Perot (FP) microcavities. This conclusion is based on results of microphotoluminescence (μ-PL) measurements performed on individual NWs, which reveal periodic undulations of the PL intensity that follow an expected pattern of FP cavity modes. The cavity is concluded to be formed along the NW axis with the end facets acting as reflecting mirrors. The formation of the FP modes is shown to be facilitated by an increasing index contrast with the surrounding media. Spectral dependence of the group refractive index is also determined for the studied NWs. The observation of the FP microcavity modes in the GaP/GaNP core/shell NWs can be considered as a first step toward achieving lasing in this quasidirect bandgap semiconductor in the NW geometry.

  • 32.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Dobrovolskiy, Alexander
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, San Diego, California, 92093, USA.
    Sukrittanon, S.
    Graduate Program of Material Science and Engineering, University of California, La Jolla, San Diego, California, 92093, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, San Diego, California, 92093, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Bouyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Novel GaP/GaNP Core/Shell Nanowires for Optoelectronics and Photonics2015In: Abstract Book, 2015, p. S8.03-Conference paper (Refereed)
  • 33.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dobrovolsky, Alexander
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, California, USA .
    Kuang, Yanjin
    Department of Physics, University of California—San Diego, La Jolla, California 92093, United States.
    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.
    Optimizing GaNP Coaxial Nanowires for Efficient Light Emission by Controlling Formation of Surface and Interfacial Defects2015In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 15, no 1, p. 242-247Article in journal (Refereed)
    Abstract [en]

    We report on identification and control of important nonradiative recombination centers in GaNP coaxial nanowires (NWs) grown on Si substrates in an effort to significantly increase light emitting efficiency of these novel nanostructures promising for a wide variety of optoelectronic and photonic applications. A point defect complex, labeled as DD1 and consisting of a P atom with a neighboring partner aligned along a crystallographic ⟨111⟩ axis, is identified by optically detected magnetic resonance as a dominant nonradiative recombination center that resides mainly on the surface of the NWs and partly at the heterointerfaces. The formation of DD1 is found to be promoted by the presence of nitrogen and can be suppressed by reducing the strain between the core and shell layers, as well as by protecting the optically active shell by an outer passivating shell. Growth modes employed during the NW growth are shown to play a role. On the basis of these results, we identify the GaP/GaNyP1–y/GaNxP1–x (x < y) core/shell/shell NW structure, where the GaNyP1–y inner shell with the highest nitrogen content serves as an active light-emitting layer, as the optimized and promising design for efficient light emitters based on GaNP NWs.

  • 34.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Dobrovolsky, Alexandr
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Sukrittanon, S.
    Tu, C. W.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Bouyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Surface and interfacial defects in coaxial GaNP nanowires2015Conference paper (Refereed)
  • 35.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Johansen, K. M.
    Borheim, T. S.
    Vines, L.
    Svensson, B. G.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Bouianova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    The Aluminum - zinc vacancy complex in ZnO: An EPR study2015Conference paper (Refereed)
  • 36.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, S. L.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Filippov, S.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    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.
    Defect properties of ZnO nanowires2014In: AIP Conference Proceedings, ISSN 0094-243X, E-ISSN 1551-7616, Vol. 1583, p. 272-276Article in journal (Refereed)
    Abstract [en]

    In this work we examined optical and defect properties of as-grown and Ni-coated ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition by means of optically detected magnetic resonance (ODMR). Several grown-in defects are revealed by monitoring visible photoluminescence (PL) emissions and are attributed to Zn vacancies, O vacancies, a shallow (but not effective mass) donor and exchange-coupled pairs of a Zn vacancy and a Zn interstitial. It is also found that the same ODMR signals are detected in the as-grown and Ni-coated NWs, indicating that metal coatings does not significantly affect formation of the aforementioned defects and that the observed defects are located in the bulk of the NWs.

  • 37.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dobrovolsky, Alexandr
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, California, USA.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, California, USA .
    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.
    Defects in GaNP Nanowires2014In: Abstract Book of the 56th Electronic Materials Conference, 2014, p. 114-Conference paper (Refereed)
  • 38.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dobrovolsky, Alexander
    Filippov, Stanislav
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, California, USA.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, California, USA .
    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.
    GaP/GaNP core/shell nanowires - a novel material system for optoelectronics and photonics2014In: Abstract Book of the 3rd Int. Conf. on Nanostructures, Nanomaterials and Nanoengineering, 2014, p. 31-Conference paper (Refereed)
  • 39.
    Dobrovolskiy, Alexander
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Stehr, Jan Eric
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, San Diego, California, 92093, USA.
    Sukrittanon, S.
    Graduate Program of Material Science and Engineering, University of California, La Jolla, San Diego, California, 92093, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, La Jolla, San Diego, California, 92093, USA.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Bouianova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Optical properties and defect formation in GaP/GaNP core/shell nanowires2014In: Program Book of the 226th Meeting of The Electrochemical Society, 2014, p. p.72-Conference paper (Refereed)
  • 40.
    Philipps, Jan M.
    et al.
    I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, D-35392 Giessen, Germany .
    Stehr, Jan Eric
    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.
    Tarun, Marianne C.
    Department of Physics and Astronomy and Materials Science Program, Washington State University, Pullman, Washington 99164-2814, USA.
    McCluskey, Matthew D.
    Department of Physics and Astronomy and Materials Science Program, Washington State University, Pullman, Washington 99164-2814, USA.
    Meyer, Bruno K.
    I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, D-35392 Giessen, Germany.
    Hofmann, Detlev M.
    I. Physikalisches Institut, Justus-Liebig-Universitaet Giessen, D-35392 Giessen, Germany.
    Recharging behavior of nitrogen-centers in ZnO2014In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 116, no 063701Article in journal (Refereed)
    Abstract [en]

    Electron Paramagnetic Resonance was used to study N2-centers in ZnO, which show a 5-line spectrum described by the hyperfine interaction of two nitrogen nuclei (nuclear spin I  = 1, 99.6% abundance). The recharging of this center exhibits two steps, a weak onset at about 1.4 eV and a strongly increasing signal for photon energies above 1.9 eV. The latter energy coincides with the recharging energy of NO centers (substitutional nitrogen atoms on oxygen sites). The results indicate that the N2-centers are deep level defects and therefore not suitable to cause significant hole-conductivity at room temperature.

  • 41.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Koteeswara Reddy, Nandanapalli
    Gwangju Institute Science and Technology, South Korea .
    Tu, Charles W.
    University of California, La Jolla, 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.
    Turning ZnO into an Efficient Energy Upconversion Material by Defect Engineering2014In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 24, no 24, p. 3760-3764Article in journal (Refereed)
    Abstract [en]

    Photon upconversion materials are attractive for a wide range of applications from medicine, biology, to photonics. Among them, ZnO is of particular interest owing to its outstanding combination of materials and physical properties. Though energy upconversion has been demonstrated in ZnO, the exact physical mechanism is still unknown, preventing control of the processes. Here, defects formed in bulk and nanostructured ZnO synthesized using standard growth techniques play a key role in promoting efficient energy upconversion via two-step two-photon absorption (TS-TPA). From photoluminescence excitation of the anti-Stokes emissions, the threshold energy of the TS-TPA process is determined as being 2.10-2.14 eV in all studied ZnO materials irrespective of the employed growth techniques. This photo-electron paramagnetic resonance studies show that this threshold closely matches the ionization energy of the zinc vacancy (a common grown-in intrinsic defect in ZnO), thereby identifying the zinc vacancy as being the dominant defect responsible for the observed efficient energy upconversion. The upconversion is found to persist even at a low excitation density, making it attractive for photonic and photovoltaic applications.

  • 42.
    Stehr, Jan Eric
    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.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Buyanova, Irina
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Unintentional Nitrogen Doping in ZnO Nanowires Revealed by Electron Paramagnetic Resonance Spectroscopy2014In: Abstract Book of the 56th Electronic Materials Conference, 2014, p. 113-Conference paper (Refereed)
  • 43.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Johansen, K. M.
    University of Oslo, Norway.
    Bjørheim, T. S.
    University of Oslo, Norway.
    Vines, L.
    University of Oslo, Norway.
    Svensson, B. G.
    University of Oslo, Norway.
    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.
    Zinc-Vacancy–Donor Complex: A Crucial Compensating Acceptor in ZnO2014In: Physical Review Applied, ISSN 2331-7019, Vol. 2, no 021001Article in journal (Refereed)
    Abstract [en]

    The aluminum–zinc-vacancy (Al Zn −V Zn ) complex is identified as one of the dominant defects in Al-containing n -type ZnO after electron irradiation at room temperature with energies above 0.8 MeV. The complex is energetically favorable over the isolated V Zn , binding more than 90% of the stable V Zn ’s generated by the irradiation. It acts as a deep acceptor with the (0/− ) energy level located at approximately 1 eV above the valence band. Such a complex is concluded to be a defect of crucial and general importance that limits the n -type doping efficiency by complex formation with donors, thereby literally removing the donors, as well as by charge compensation.

  • 44.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, Faculty of Science & Engineering.
    Chen, Shula
    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, Faculty of Science & Engineering.
    Devika, M
    Gwangju Institute Science and Technology, South Korea .
    Koteeswara Reddy, N
    Gwangju Institute Science and Technology, South Korea .
    Tu, C W
    Gwangju Institute Science and Technology, South Korea University of Calif San Diego, CA 92093 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.
    Defect properties of ZnO nanowires revealed from an optically detected magnetic resonance study2013In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 24, no 1, p. 015701-Article in journal (Refereed)
    Abstract [en]

    Optically detected magnetic resonance (ODMR) complemented by photoluminescence measurements is used to evaluate optical and defect properties of ZnO nanowires (NWs) grown by rapid thermal chemical vapor deposition. By monitoring visible emissions, several grown-in defects are revealed and attributed to Zn vacancies, shallow (but not effective mass) donor and exchange-coupled pairs of Zn vacancies and Zn interstitials. It is also found that the intensity of the donor-related ODMR signals is substantially lower in the NWs compared with that in bulk ZnO. This may indicate that formation of native donors is suppressed in NWs, which is beneficial for achieving p-type conductivity.

  • 45.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Knutsen, K. E.
    Svensson, B. G.
    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.
    Defects in Electron Irradiated ZnO: An Electron Paramagnetic Resonance Study2013In: 2013 MRS Fall Meeting, 2013Conference paper (Refereed)
  • 46.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Wang, Xingjun
    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.
    Pearton, S J.
    University of Florida, FL USA .
    Gueorguiev Ivanov, Ivan
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor 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.
    Defects in N, O and N, Zn implanted ZnO bulk crystals2013In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 10, p. 103509-Article in journal (Refereed)
    Abstract [en]

    Comprehensive characterization of defects formed in bulk ZnO single crystals co-implanted with N and Zn as well as N and O atoms is performed by means of optically detected magnetic resonance (ODMR) complemented by Raman and photoluminescence (PL) spectroscopies. It is shown that in addition to intrinsic defects such as Zn vacancies and Zn interstitials, several N-related defects are formed in the implanted ZnO. The prevailed configuration of the defects is found to depend on the choices of the co-implants and also the chosen annealing ambient. Specifically, co-implantation with O leads to the formation of (i) defects responsible for local vibrational modes at 277, 511, and 581 cm−1; (ii) a N-related acceptor with the binding energy of 160 ± 40 meV that is involved in the donor-acceptor pair emission at 3.23 eV; and (iii) a deep donor and a deep NO acceptor revealed from ODMR. Activation of the latter defects is found to require post-implantation annealing in nitrogen ambient. None of these defects are detected when N is co-implanted with Zn. Under these conditions, the dominant N-induced defects include a deep center responsible for the 3.3128 eV PL line, as well as an acceptor center of unknown origin revealed by ODMR. Formation mechanisms of the studied defects and their role in carrier recombination are discussed.

  • 47.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, S. L.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Knutsen, K. E.
    Svensson, B. G.
    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.
    Electron Paramagnetic Resonance Investigations of Defects in Electron Irradiated ZnO2013Conference paper (Other academic)
  • 48.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Dobrovolsky, Alexandr
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Kuang, Y. J.
    Department of Physics, University of California, La Jolla, California, USA.
    Sukrittanon, S.
    Graduate Program of Materials Science and Engineering, La Jolla, California, USA .
    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.
    Optically detected magnetic resonance investigation of GaP and GaP/GaNP/GaNP Nanowires2013In: 2013 MRS Fall Meeting, 2013Conference paper (Refereed)
  • 49.
    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.

  • 50.
    Stehr, Jan Eric
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials. Linköping University, The Institute of Technology.
    Chen, S. L.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    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.
    Photo-EPR and Photoluminescence Excitation Studies of Defects/Impurities Responsible for Upconversion Effects in Bulk ZnO crystals.2013Conference paper (Refereed)
12 1 - 50 of 56
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