EPR investigations of SiC and SiOC nanometric powders

Abstract

Abstraer. EPR investigations are performed in SiC and SiOC nanometric powders armealed between 1200 and 1800~ By using different EPR frequency bands anda suitable speetra analysis, three quite different paramagnetic defects with well defined gi (i = 1, 2, 3) and hyperfme ,~ (i = 1, 2) tensors aeeount for the EPR signal in these materials. The defeets are charaeterized by gl (g~q= 2.0046(3), g~~ = 2.0023(3)), g2 (g~~ = 2.0037(3), g~ = 2.0028(3)) and an isolropic g3 (2.0030(3)) tensors. In SiC powders, the defects assignment is discussed with respeet to the different SiC forms, namely tx-SiC and 13-SiC polytypes as well as amorphous SiC and earbon present in minor eoncentration in the network. In SiOC powders, the above defeets are evideneed only at high annealing temperature (T, >_ 1200~ when the oxygen contained is highly redueed.

Investigation of the paramagnetic centres and electronic properties of silicon carbide nanomaterials

“…According to the procedure described previously for SiC and SiOC nanomaterials [11], the paramagnetic centres are S = 1/2 defects interacting with N equivalent neighbouring nuclei of 29 Si or 13 C (nuclear spin I = 1/2) and with an applied magnetic field H st . Each paramagnetic centre is described by the following spin Hamiltonian:…”