Structural differences between deuterated and hydrogenated silicon nitride/oxynitride

Hydrogenated and deuterated silicon nitride (a-SiN_x:H and a-SiN_x :D) and silicon oxynitride (a-SiO_xN_y, :H and a-SiO_xN_y :D) films are prepared by plasma-enhanced chemical vapor deposition. Their transmission and photoluminescence spectra were measured. Both the photoluminescence and transmission spectra show that the deuterated films have higher energy gaps than those of the hydrogenated films in the same growth condition. The infrared absorption spectra of these samples are identified and compared in detail. From the infrared spectra, the interaction between N-D bond rocking vibration and Si-N bond stretching vibration is observed, which pushes N-D bond rocking vibration to a higher energy. It is also observed that the refractive index of deuterated film is lower than the hydrogenated film in the same growth condition due to its lower density.