XANES and XEOL investigations of SiC microcrystals and SiC nanowires

Abstract

X-ray absorption near-edge structures (XANES) at Si and C K-edge as well as X-ray excited optical luminescence (XEOL) have been used to investigate the electronic structures and optical properties of SiC microcrystals (SiCmcs) and SiC nanowires (SiCnws). SiCnws synthesized via thermal evaporation, have a SiC (β-phase)-core-SiO2-shell morphology. We found that the XANES for SiCmcs, a 6H-SiC (α-phase) structure, shows reasonable agreement with density functional theory (DFT) calculations. As for SiCnws, we observed both SiO2 and SiC features at the Si K-edge. It is interesting to note that upon X-ray excitation, SiCmcs emit bright light at the wavelength of 600 nm (2.07 eV), although bulk α-SiC has an indirect band-gap of 3.02 eV. SiCnws, on the other hand, exhibit luminescence at 460 nm with a shoulder at 600 nm. The analysis of these data and its implications are presented. © 2009 IOP Publishing Ltd.