Microstructure Properties Of Silicon Nanograins/silicon Nitride Thin Films

Silicon-rich hydrogenated silicon nitride thin films (a-SiNx:H) are deposited by helicon wave plasma-enhanced chemical vapor deposition (HWP-CVD) technique. The influence of the thermal annealing on the microstructure modification and optical absorption properties of silicon nanoparticles (Si NPs) embedded in silicon nitride thin films (Si NPs/SiNx) are mainly concerned. The structural characterization and optical absorption properties of the films are analyzed by Raman scattering spectra, Fourier-transform infrared spectroscopy (FTIR), Atom Force Microscope (AFM), optical absorption and photoluminescence (PL) spectra. The microstructure of thin film properties are investigated in detail, and also investigate a basis for the future thermal annealing controlling and device applications of a-SiNx:H films.The films with the Si NPs/SiNx structure are obtained at low temperature by controlling the HWP-CVD conditions. The silicon nanocrystals thin films with embedded structure are synthesized directly by controlling hydrogen-diluted amount properly in reactant gas and the modification role is revealed to the microstructure of the films by introducing hydrogen in the reactant. It has been shown that the hydrogen dilution is beneficial to not only enhancing structure order degree and Si NPs crystallinity but also decreasing density of defect states.In the different environment(N2,FG--10%H2 and 90%N2,H2)at 800℃, the effect of thermal annealing on the microstructure of Si NPs/SiNx thin films is analyzed. The results show that the density of defect states and structure disorder degree increase, and the optical band gap decreases. The annealing process induces the decrease of Si-H and N-H binding densities. However the phase transition from amorphous to nanocrystalline Si NPs is not achieved after thermal annealing.The effect of Rapid Photo-thermal annealing (RPTA) on the microstructure of Si NPs /SiNx thin films is investigated. The Raman spectroscopy shows the crystallization of amorphous Si NPs after RPTA treatment at the lower annealing temperature (700℃). The strong tunable visible PL at room temperature is obtained from Si NPs due to the QCE by adjusting the reaction gas flow ratio through the RPTA.