Temperature dependent optical properties of Si nanocrystals embedded in SiO2 matrix

The optical properties of Si nanocrystals (nc-Si) with different sizes (2∼5 nm) embedded in a SiO2 matrix synthesized by the SiO x /SiO2 superlattice approach were studied in a temperature range from room temperature to 600 K by spectroscopic ellipsometry. The Maxwell–Garnett effective medium approximation and Lorentz oscillator model were employed to extract the dielectric function of nc-Si. The results show that the temperature dependence of optical properties of nc-Si is sensitive to its size. An empirical expression of Varshni approximation was obtained to characterize the band-gap energy change of nc-Si at different temperatures.