Photoluminescence origin of nanocrystalline SiC films

The nanocrystalline SiC films were prepared on Si (111) substrates by rf magnetron sputtering and then annealed at 800°C and 1000°C for 30 minutes in a vacuum annealing system. The crystal structure and crystallization of as-annealed SiC films were determined by the Fourier transform infrared (FTIR) absorption spectra and the X-ray diffraction (XRD) analysis. Measurement of photoluminescence (PL) of the nanocrystalline SiC (nc-SiC) films shows that the blue light with 473 nm and 477 nm wavelengths emitted at room temperature and that the PL peak shifts to shorter wavelength side and the PL intensity becomes stronger as the annealing temperature decreases. The time-resolved spectrum of the PL at 477 nm exhibits a bi-exponential decay process with lifetimes of 600 ps and 5 ns and a characteristic of the direct band gap. The strong blue light emission with short PL lifetimes suggests that the quantum confinement effect of the SiC nanocrystals resulted in the radiative recombination of the direct optical transitions. The project supported by the National Natural Science Foundation of China (Grant No. 60476003)