Properties of hydrogenated amorphous Si-N films prepared by r.f. magnetron sputtering with emphasis on the non-stoichiometric region

Abstract

The results of optical absorption, IR absorption, Raman scattering and conductivity measurements for hydrogenated amorphous Si-N films (a-Si_1-xN_x:H) prepared by r.f. magnetron sputtering have been presented. The variation in the nitrogen flow rate reveals three distinct regions: region A, a-Si_1-xN_x:H, where a kind of doping effect is shown in the conductivity, possibly due to the presence of fourfold-coordinated nitrogen atoms together with threefold-coordinated nitrogen atoms; region B, a-Si_1-xN_x:H with mainly threefold-coordinated nitrogen atoms; region C, Si₃N_4, with an optical gap near that of the stoichiometric compound. Effects of variation in hydrogen flow rate and substrate temperature have been studied for films in region B. A detailed investigation of light-induced changes for a-Si_1-xN_x:H films deposited with different nitrogen and hydrogen flow rates has been carried out. The results obtained indicate that films with a larger nitrogen content are more vulnerable to light-induced degradation.