Intrinsic defects in nonstoichiometric B-SiC nanoparticles studied by pulsed magnetic resonance methods

摘要

Nonstoichiometric B-SiC nanoparticles (np-SiC) have been studied by electronudparamagnetic resonance (EPR) and pulsed magnetic resonance methods including fieldudswept electron spin echo (FS ESE), pulsed electron nuclear double resonance (ENDOR)udand hyperfine sublevel correlation spectroscopy (HYSCORE). Four ESE signals relatedudto the paramagnetic centers labeled D1, D2, D3, D4 with g = 2.0043, g = 2.0029,udg = 2.0031, g = 2.0037 were resolved in FS ESE spectrum due to their different spinudrelaxation times. As deduced from the study of the superhyperfine structure of the D2uddefect by FS ESE, pulse ENDOR and HYSCORE methods the dominant paramagneticudcenter is a carbon vacancy (Vc) localized in B-SiC crystalline phase of the np-SiC. Theudparameters of the D2 center coincide with those found for the Vc in np-SiC obtained byudlaser pyrolysis method. Three other defects were identified by comparison of their EPRudparameters with the microstructure of the np-SiC. The D1 defect was attributed to the Vcudvacancy located in a-SiC crystalline phase. The D3 defect is identified with the carbonuddangling bonds located in the carbon excess phase. The D4 defect was assigned to audthreefold-coordinated Si atom bonded with one nitrogen atom, resulting in the formationudof the local bonding Si-Si2N configuration in a-Si3N4 phase.