Papers by Keyword: Electron Paramagnetic Resonance (EPR)

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Authors: K. Irmscher, W. Gehlhoff, Y. Tomm, H. Lange
Authors: Z. Zolnai, Nguyen Tien Son, Björn Magnusson, Christer Hallin, Erik Janzén
Authors: M.M. Afanasjev, R. Laiho, L.S. Vlasenko, M.P. Vlasenko
Authors: Larysa Khomenkova, M. Baran, Oleksandr Kolomys, Victor Strelchuk, Andrian V. Kuchuk, V.P. Kladko, J. Jedrzejewski, I. Balberg, Y. Goldstein, Philippe Marie, Fabrice Gourbilleau, N. Korsunska
Abstract: RF magnetron sputtering of two separate silicon and oxide (SiO2 or Al2O3) targets in pure argon plasma was used for deposition of Six(SiO2)1-x and Six(Al2O3)1-x films with x=0.15-0.7 on long fused quarts substrate. The effect of post-fabrication treatments on structural and light emitting properties of the films with different x values was investigated by means of Raman scattering, electron paramagnetic resonance and X-ray diffraction as well as by photoluminescence (PL) methods. The formation of amorphous Si clusters upon deposition process was found for the both types of films. The annealing treatment at 1150°C during 30 min results in formation of Si nanocrystallites (Si-ncs). The latter were found to be larger in Six(Al2O3)1-x films than that in Six(SiO2)1-x counterparts with the same x values and are under tensile stresses. The investigation of photoluminescence properties of annealed films of both types revealed the appearance of visible-near infrared light emission. The Six(SiO2)1-x films demonstrated one broad PL band which peak position shifts gradually to from 1.4 eV to 1.8 eV with the x decrease. Contrary to this, for the Six(Al2O3)1-x films two overlapped PL bands were observed in the 1.4-2.4 eV spectral range with peak positions at ~2.1 eV and ~1.7 eV accompanied by near-infrared tail. Comparative analysis of PL spectra of both types samples showed that the main contribution to PL spectra of Six(SiO2)1-x films is given by exciton recombination in the Si-ncs whereas PL emission of Six(Al2O3)1-x films is caused mainly by carrier recombination either via defects in matrix or via electron states at the Si-ncs/matrix interface.
Authors: Patrick Carlsson, Nguyen Tien Son, T. Umeda, Junichi Isoya, Erik Janzén
Abstract: The SI-5 electron-paramagnetic-resonance (EPR) centre is a dominant defect in some high-purity semi-insulating (HPSI) SiC substrates and has recently been shown to originate from the negatively charged carbon vacancy-carbon antisite pair (VC − Si C ). In this work, photoexcitation EPR (photo-EPR) was used for determination of the energy position of deep acceptor levels of VCCSi in 4H-SiC. Our photo-EPR measurements in slightly n-type material show an increase of the EPR signal of VC − Si C for photon energies from ~0.8 eV to ~1.3 eV. Combining the data from EPR, deep level transient spectroscopy and supercell calculations we suggest that the (1–|2–) levels of the different configurations of the defect are located in the range ~0.8-1.1 eV below the conduction band.
Authors: Ivan V. Ilyin, Alexandra A. Soltamova, V.A. Soltamov, V.A. Khramtsov, E.N. Mokhov, P.G. Baranov
Abstract: Electron paramagnetic resonance (EPR) at X-band (9.4 GHz) and Q-band (35 GHz) have been used to study defects in two samples of AlN monocrystals, grown by a sublimation sandwich method. These investigations reveal the presence of Fe2+ impurities in the reddish sample. The spectra of substitutional Fe2+ are highly anisotropic and could be observed even up to the room temperature. After illumination the signals showing the DX behavior were detected in the same sample. We assume these signals to arise due to the presence of the shallow donor center namely the isolated substitutional oxygen ON occupying the nitrogen position. In the second slightly amber-coloured sample EPR measurements before and after X-ray showed the presence of a deep-donor center which was assumed to be nitrogen vacancy VN. Based on thermoluminescence measurements the depth of the level was estimated to 0.45-0.5 eV.
Authors: Mary Ellen Zvanut, G. Ngetich, H.J. Chung, A.Y. Polyakov, Marek Skowronski, N.Y. Garces, E.R. Glaser
Abstract: The understanding of the structure and associated defect level of point defects in SiC is important because the material is to be used both as a semiconductor and semi-insulator. Production of the latter is achieved by compensation of unavoidable impurities using defects that require more energy for ionization than the unintentional donors or acceptors. The purpose of the present work is to measure the defect energy level of one center in high resistivity 4H SiC using photo-induced electron paramagnetic resonance (photo-EPR). The center is identified as SI-5, an EPR signal that others have attributed to the negative charge state of the carbon vacancy-carbon antisite pair, − C Si V C . Samples containing this defect exhibit two different photo thresholds, which depend on the resistivity activation energy, Ea. For samples with Ea less than 0.8 eV, a photothreshold at 0.75+/- 0.05 eV is observed, but for those with Ea greater than 0.8 eV, the threshold is between 2 and 2.5 eV. Previous work focused on the former case. Here, the SiC substrates with the larger Ea are emphasized, showing that the photo-threshold likely measures the neutral to negative defect level, − / 0 C Si V C .
Authors: Lesya P. Yurchenko, Igor P. Bykov, Alexander B. Brik, Oleksandr D. Vasylyev, Valeriy G. Vereschak, Gunnar Suchaneck, Lubomir Jastrabik, Alexandr Dejneka
Abstract: The formation mechanisms of paramagnetic centers originating from Zr3+ and Cr3+ ions and the influence of the nanoparticle composition on thermal generation processes of these paramagnetic centers in ZrO2 structure were studied by electron paramagnetic resonance. A set of nanosized zirconium oxide powders (nominally pure ZrO2, ZrO2 doped with correspondingly Y2O3 and Sc2O3, Cr2O3 and Y2O3, as well as Cr2O3) was investigated: The influence of annealing on the EPR lines of Zr3+ and Cr5+ ions was found to be different. Annealing curves of EPR signals caused by Cr5+ ions have a maximum in temperature range 500–600 °C. Mechanisms of Zr3+ and Cr5+ ions formation were discussed.
Authors: D.M. Hofmann, B.K. Meyer, P. Christmann, T. Wimbauer, W. Stadler, A. Nikolov, A. Scharmann, A. Hofstätter
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