Petrenko T. Paramagnetic defects in silicon oxides with nanocrystallites and p-type silicon carbide.

The Thesis is devoted to EPR investigations of paramagnetic defects in Si- and Ge-implanted SiO2 layers, SiOx films prepared by thermal evaporation of SiO and electron-irradiated p-type 6H-SiC. In the latter case experimental research was performed in conjunction with quantum- chemical simulation of the radiation defects in SiC. A number of paramagnetic defects in SiO2 layers and SiOx films were identified by EPR. A character of structural changes during the annealing of films in the temperature range of 100?1100 0С has been determined. Besides distinct well-known oxygen-vacancy associated defects in SiO2 and nonbridging oxygen hole centers, two new defects related to excess of Si atoms and presence of Ge atoms in SiO2 matrix have been revealed. In the case of SiOx films the EPR spectra of the Pb centers were detected for the first time at the interface of randomly oriented silicon nanocrystallites and SiO2. Spin Hamiltonian parameters for the Ky1, Ky2 and Ky3 centers observed in the electron-irradiated p-type 6H-SiC have been determined in the temperature range of 4–300 K. Comparison of experimentally observed hyperfine parameters with those derived from the density functional calculations of electronic structure for various defects has led to the unambiguous assignment of these centers to the positively charged carbon vacancy located in three inequivalent lattice sites of 6H-SiC. The well-known T5 and EI3 defects in electron-irradiated SiC have been also identified on a base of first principle studies as carbon <100>-split interstitial in charged and neutral state, respectively.