Self-organized growth and optical emission of silicon-based nanoscale β-SiC quantum dots

Si-based beta-SiC quantum dots (QDs) were fabricated for exploring efficient blue emission from beta-SiC nanostructures. Microstructural observations and x-ray photoemission spectroscopy reveal that the beta-SiC QDs with sizes of 5-7 nm are embedded in the SiO2 and graphite matrices, displaying a locally tetragonal symmetry. Photoluminescence spectral examinations show two narrow blue-emitting bands at 417 and 436 nm, which are determined by both quantum confinement and surface structure of the beta-SiC QDs. Electron spin resonance investigation demonstrates that the photoexcited carriers partially come from the beta-SiC QD core with a widened band gap, whereas the radiative recombination occurs in Si excess defect centers at the beta-SiC QD surface. A theoretical calculation about electronic states caused by the vacancy defects in the gap of balls formed with excess Si atoms at the surfaces of the beta-SiC QDs supports our assignment to the two blue-emitting origin. (C) 2003 American Institute of Physics.