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

Abstract

Homogeneous SiO x 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 SiO x 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 N 2 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/SiO x 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).