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The physical properties of the pramagnetic nitrogen donors in the silicon carbide monocrystalls and nanopowders


Author: Savchenko D.V.


Presented by National Technical University of Ukraine "Kyiv Polytechnic Institute'"


A series consists of 1 monograph,15 scientific papers and 15 abstracts presented at Ukrainian and international conferences, published during 2009-2013 years and devoted to the study of the physical properties of nitrogen donors in silicon carbide monocrystals and nanopowders by the continuous wave and pulse magnetic resonance methods.

The paramagnetic triplet center (S = 1) was found in n-type silicon carbide monocrystals of 4H and 6H polytypes and was assigned with the distant nitrogen donor pair residing quasi-cubic and hexagonal positions in the silicon carbide lattice, that are coupled by the silicon atom. The formation of this pair does not depend on the growth method of silicon carbide monocrystals and nitrogen donor concentration.

The new idea that the nitrogen donors can substitute not only carbon sites, but the silicon sites with the deep energy levels in the bandgap in the 6H and 15R polytypes of silicon carbide was proposed.

The magnetic and electric properties of conduction electrons in the n-type silicon carbide monocrystals of 4H and 6H polytypes was obtained. In the highly nitrogen doped silicon carbide monocrystals of 6H polytype the insulator-metal transition (Mott transition) was observed. It was found that the transition temperature depends on the nitrogen donor concentration.

In self-assembled silicon carbide nanosturctures, obtained by the planar diffusion technique without preliminary irradiation, the paramagnetic nitrogen-vacancy center in the triplet state (S = 1) was detected and has a practical significance for the spintronics, particularly for the development of qubits.

In the semi-insulating silicon carbide substrates of 4H polytype the processes of persistent photoconductivity and relaxation of the non-equilibrium charge carriers, trapped on the defect and impurity centers, where experimentally and theoretically described. The kinetic characteristics of photosensitive paramagnetic centers (in particular nitrogen donors) and the probability of the electron and hole transitions between them after termination of the photoexcitation were obtained. The most efficient electron processes responsible for the persistent photoconductivity and relaxation in the semi-insulating silicon carbide substrates of 4H polytype were established.

The quantum size effect for nitrogen donors in the silicon carbide nanopowders was found and results in the delocalization of the nitrogen donor wave function with the particle size decrease (d < 50 nm).

The results of theinvestigation concerning the theme of the work are presented in: 1 monograph,15 papers(14 in the international journals that are included in the Scopus database) and 15– conference abstracts. The overall citing index of the papers presented by the author is 78 (according to the Scopus database), h-index=5.

Total number of publications of the author – 90: among them 2 monographs, 38 – scientific papers, 50 – conference abstracts.