Enhanced visible photoluminescence from nc-Si/SiOx films deposited by electron beam evaporation

Homogeneous SiOx thin films were deposited on Si substrates by the electron beam evaporation technique in an ultra-high vacuum apparatus. The structures of the samples annealed at 1000 °C were analyzed by high resolution transmission electron microscopy (HRTEM). HRTEM observation reveals that the thin films contain nanocrystalline silicon (nc-Si) grains with average diameters in the range from 3.0 to 4.5 nm, embedded in an amorphous SiOx matrix. Raman and Fourier transform infrared transmission (FTIR) results reveal the occurrence of phase transitions from amorphous silicon (a-Si) to nc-Si after the samples were annealed in N2 at temperatures above 1000 °C for 1 h. An enhanced photoluminescence (PL) signal with a peak at 760 nm was observed for samples annealed at 1000 °C. While the PL peaks for samples annealed below 1000 °C are related to Si–O bonds at the a-Si/SiOx interfaces, the PL peaks for samples annealed above 1000 °C are attributed to the Si=O bonds at the surface of nc-Si and the formation of intermediate state of silicon (IPSS).