Structure and optical properties of SiN x : H films with Si nanoclusters produced by low-frequency plasma-enhanced chemical vapor deposition

The SiN x : H films with compositions differently deviating from the stoichiometric proportion are produced by low-frequency plasma-enhanced chemical vapor deposition at the temperatures 100 and 380°C. Deviations from the stoichiometric composition are varied by varying the ratio between the ammonia and monosilane fluxes from 0.5 to 5. The films are studied by ellipsometry, Raman spectroscopy, infrared absorption spectroscopy, and luminescence measurements. In the SiN x : H films (x < 4/3), amorphous silicon clusters were found. According to estimations, only a small fraction of excess silicon coalesces into clusters, and an increase in the substrate temperature stimulates clustering. It is found that, with increasing the content of excess silicon in the films, the photoluminescence peak shifts to longer wavelengths.