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Опубликовано 2010-00-00 Опубликовано на SciPeople2010-12-10 14:24:12 ЖурналPhysical Review B

EPR study of carbon and silicon related defects in carbon-rich hydrogenated amorphous silicon-carbon films
E. N. Kalabukhova, S. N. Lukin, D. V. Savchenko, B. D. Shanina, A. V. Vasin, V. S. Lysenko, A. N. Nazarov, A. V. Rusavsky, J. Hoentsch, Y. Koshka / Дария Савченко
Аннотация Three paramagnetic defects were revealed in amorphous hydrogenated carbon-rich silicon-carbon alloy films a-Si0.3C0.7:H. Two of them were attributed to silicon Si dangling bonds Si DBs and carbon-related defects CRDs. The third defect, based on its g-value and linewidth, was tentatively attributed to a bulk Si DB defect bonded with nitrogen atoms in Si-N2Si configuration. The effect of thermal vacuum annealing on the properties of the a-Si0.3C0.7 :H films was studied in the temperature range of Tann=400–950 °C. A strong increase in CRD concentration was observed in high temperature annealed a-Si0.3C0.7 :H films, which was explained by hydrogen effusion process occurred at Tann above 400 °C. The increase in the concentration of the CRDs is accompanied by the exchange narrowing of its electron paramagnetic resonance EPR linewidth due to the formation of carbon clusters having ferromagnetic ordering. The temperature dependent g-factor anisotropies observed at Q-band and D-band frequencies for the CRD signal in the samples annealed at high temperature 950 °C were explained by the presence of graphitelike sp2-coordinated carbon clusters and demagnetization field shape-dependent anisotropy term. The demagnetizing field Bdem=−4Ms, where Ms is the sample magnetization, was found to be equal to 0.44 mT at 37 GHz and 1.1 mT at 140 GHz. Analysis of the temperature dependences of the integral intensities of the SiDB and CRD EPR signals has shown that they do not obey the Curie-Weiss law, and their spin systems exhibit superparamagnetic and ferromagnetic properties, respectively.
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