Stabilization of Si rich nitride phase by swift heavy ion irradiation in non-stoichiometric a-SiNx:H thin films

We report the effect of swift heavy ion irradiation on non-stoichiometric hydrogenated amorphous silicon nitride films (a-SiNx:H), grown on Si substrate by Photo- Chemical vapor deposition. A significant increase in refractive index of films due to Si rich phase stabilization upon irradiation is observed, which is supported by UV-Vis spectroscopy. Further, X-ray photoelectron spectroscopy (XPS) shows the improved Si rich SiNx phase at surface of films. Fourier transform Infrared spectroscopy suggests increased bond density of Si-N in thin films. This is due to out-diffusion of hydrogen upon ion irradiation as bond density for Si-H decreases upon irradiation. It leads to phase separation and stabilization of Si rich nitride phase as unbounded excess Si and N further form Si-Si or Si-N bond configuration, resulting in prominent Si rich silicon nitride phase.