Pulsed EPR and ENDOR Study of SiC Nanopowders

Abstract

The great potential of the micro(mp) nano-particle (np) silicon carbide (SiC) for future applications in spintronics stimulates detailed studies of the effects of impurities and defects in their electronic properties. In particular, mpand np-SiC doped with nitrogen (N) atoms is an important issue to be investigated, since N is a common contaminant in SiC bulk, acting as n-type dopant. Although N has been found to be present in the nanomaterials, there is no experimental evidence indicating for the formation of the N shallow donor state in np-SiC. The np-SiC samples with R 50 nm which was identified by pulsed ENDOR as the N in quasi-cubic (Nk2) site. As the size of the np-SiC decrease, the signal from VC in 6H SiC phase appeared in the FS ESE spectrum, which gives rise to the compensation of the N donors and as a result the FS ESE spectrum intensity of N decrease significantly. Only two signals due to the VC located in 3C and 6H SiC phase were observed in the FS ESE spectrum of the np-SiC samples with the R < 50 nm. The fact that the ENDOR signal centered at the hydrogen (H) nuclear Larmor frequency (n) was observed in the np-SiC with R < 100 nm indicates that H atoms are localized in the vicinity of the VC and can form the H-related defect like (VC+H). As a conclusion, two phases (and -SiC crystalline phases) are presented in np-SiC. The work was supported by GA CR 13-06697P and SAFMAT project CZ.2.16/3.1.00/22132.