Comparative analysis of photoluminescence in nano-sized amorphous and crystalline silicon embedded in silicon nitride thin film

Nano-sized amorphous silicon embedded in SiNx films are prepared by helicon wave plasma-enhanced chemical vapor deposition technique (HWP-CVD), and Si nanocrystals embedded in SiNx films is obtained after furnace annealing (FA) in nitrogen ambient. The structure and optical properties of nano-sized amorphous and crystalline silicon embedded in silicon nitride (SiNx) thin film is comparatively analyzed. Raman scattering measurement shows that, apart from appearance of a new peak at about 496-510cm(-1) corresponding to Si nanocrystals scattering, the relative scattering intensity of the two peaks located at 150 cm(-1) and at 480 cm(-1) increases after high temperature annealing, indicating that the microstructures of the annealed films becomes more disordered. Meanwhile, the photothermal deflection spectra (PDS) show the optical absorption coefficient of annealed samples in the band gap increases in about one order of magnitude, indicating that more gap states exist in the annealed samples. After further annealing in forming gas and comparing the PL results of both as-deposited and thermal treatment thin film, it is found that red shift of the main peak of PL spectra is correlated with the enlarge of the silicon size. The role of interface states between silicon clusters and SiNx matrix influence the PL behavior is discussed.