Papers by Author: Ekaterina N. Kalabukhova

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Authors: B.D. Shanina, Ekaterina N. Kalabukhova, S.N. Lukin, E.N. Mokhov
Authors: Siegmund Greulich-Weber, M. März, Johann Martin Spaeth, E.N. Mokhov, Ekaterina N. Kalabukhova
Authors: Ekaterina N. Kalabukhova, S.N. Lukin, E.N. Mokhov, B.D. Shanina
Authors: Ekaterina N. Kalabukhova, Dariya Savchenko, Bela Shanina, Nikolai T. Bagraev, Leonid Klyachkin, Anna Malyarenko
Abstract: Triplet center with spin state S = 1 is detected in the EPR spectrum of the self-assembled 6H SiC nanostructure obtained by non-equilibrium boron diffusion into the n-type 6H SiC epitaxial layer (EL) under conditions of the controlled injection of the silicon vacancies at the temperature of T = 900°C. From the analysis of the angular dependences of the EPR spectrum and the numerical diagonalization of the spin Hamiltonian, the value of the zero-field splitting constant D and g-factor are found to be D = 1140•10-4см-1 and gpar = 1.9700, gper = 1.9964. Based on the hyperfine (hf) structure of the defect originating from the hf interaction with one 14N nuclei, the large value of the zero-field splitting constant D and technological conditions of the boron diffusion into the n-type 6H SiC EL, the triplet center is tentatively assigned to the defect center consisting of nitrogen atom and silicon vacancy.
Authors: Ekaterina N. Kalabukhova, S.N. Lukin, D.V. Savchenko, W.C. Mitchel, Siegmund Greulich-Weber, Uwe Gerstmann, Andreas Pöppl, J. Hoentsch, E. Rauls, Yurii Rozentzveig, E.N. Mokhov, Mikael Syväjärvi, Rositza Yakimova
Abstract: D-band electron paramagnetic resonance (EPR) measurements as well as X and Q-band field-swept Electron Spin Echo (ESE) and pulsed Electron Nuclear Double Resonance (ENDOR) studies were performed on a series of n-type 4H-SiC wafers grown by different techniques including sublimation sandwich method (SSM), physical vapor transport (PVT) and modified Lely method. Depending on the C/Si ratio and the growth temperature the n-type 4H-SiC wafers revealed, besides a triplet due to nitrogen residing on the cubic site (Nc), two nitrogen (N) related EPR spectra with g||=2.0055, g⊥=2.0010 and g||=2.0063, g⊥=2.0005 with different intensities. In the samples with low C/Si ratio the EPR spectrum with g|| =2.0055, g⊥=2.0010 consists of a triplet with low intensity which is tentatively explained as a N-related complex, while in the samples with high C/Si ratio the triplet is transformed into one structureless line of high intensity, which is explained as being due to an exchange interaction between N donors. In the samples grown at low temperature with enhanced carbon concentration the EPR line with g||=2.0063, g⊥=2.0005 and a small hyperfine (hf) interaction dominates the EPR spectrum. It is attributed to N on the hexagonal lattice site. The interpretation of the EPR data is supported by activation energies and donor concentrations obtained from Hall effect measurements for three donor levels in this series of 4H-SiC samples.
Authors: Ekaterina N. Kalabukhova, S.N. Lukin
Authors: Ekaterina N. Kalabukhova, D.V. Savchenko, Siegmund Greulich-Weber, M.F. Bulanyi, S.A. Omelchenko, O.V. Khmelenko, A.A. Gorban, E.N. Mokhov
Abstract: In this paper, we report on a photoluminescence (PL) and EPR study of several semiinsulating (SI) 4H SiC samples showing the different compensation regimes due to the presence of V4+ and V3+of different concentration. The samples which contain only V3+ indicates the compensation regime NV≅ND-NA>0 with the Fermi level located in the upper half of the band gap. The presence of V4+ along with V3+ in the other two set of samples indicates the SI behavior of the samples with compensation regime NV>NA-ND>0. Considering that the samples revealed EPR spectrum of vanadium V3+, position of the Fermi level should be also in the upper half of the band gap and mixed conductivity could be expected. UD-3 PL spectrum was observed in vanadium doped SI 4H SiC presented in the samples in V3+/V4+ and V4+/V5+ charge states with compensation regime NV>NA-ND>0. The data obtained prove that the PL and EPR are suitable techniques in determination SI yield in SiC crystal.
Authors: D. Savchenko, Ekaterina N. Kalabukhova, A. Sitnikov, A.V. Vasin, S. Starik, O. Gontar, G. Rudko, A.N. Nazarov, V.S. Lysenko, V. Tertykh
Abstract: The carbonized silica (SiO2:C) nanopowders were prepared by chemical modification of fumed silica (aerosil) by phenyltrimethoxysilane followed by thermal annealing at temperature in range of 500-800 °C in nitrogen flow. Their magnetic properties were investigated by electron paramagnetic resonance (EPR) in the temperature range from 4.2 K to 292 K. The initial and annealed SiO2:C samples revealed carbon (C) related defects. The carbon related radicals (CRR) in annealed SiO2:C nanopowders with g-factors 2.0042, 2.0039 were attributed to the oxygen (O)-centered CRR and C-centered CRR with a nearby O heteroatom, respectively. The EPR data were compared with infrared (IR) and photoluminescence (PL) data. It was found that the position of the PL band depends on the type of CRR formed after sample annealing. The PL with maximum intensity at 440 nm was found for the sample annealed at 500°C in which O-centered CRR was observed while in the sample annealed at 600°C in which C-centered CRR with a nearby O heteroatom was observed and graphite-like amorphous C clusters were appeared the peak of the PL band was shifted to the 510-520 nm.
Authors: B.D. Shanina, Ekaterina N. Kalabukhova, S.N. Lukin, E.N. Mokhov
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