A study of the optical and electronic properties of amorphous silicon nitride.

Amorphous a-SiNx (:H) films have been prepared by radio-frequency sputtering in an argon-nitrogen-hydrogen atmosphere. Both hydrogenated and non-hydrogenated films were studied along with films prepared by the glow-discharge decomposition of a gaseous mixture of silane and ammonia. Photoemission experiments were performed on the sputtered samples. The position and strength of the core levels were determined, along with the plasma energies as a function of x. A comprehensive study of the number and types of defects present within a-SiN(:H) was undertaken. Films sputtered at room temperature and at 200°C, both with and without hydrogen, were studied along with films prepared by the glow-discharge technique. The results obtained are discussed in the light of existing models. Certain characteristic energies obtainable from optical data have been found for hydrogenated and non-hydrogenated films. These results are then related to other experimental results, in particular those from photoemission measurements. Reflection measurements have been made in the range 0.5eV to 12eV on the sputtered and glow-discharge films. From the reflection measurements e2 spectra were determined by Kramers-Kronig analysis. The dependence of the optical joint density of states with alloying was found from the data. It was found from these measurements that the top of the valence band gradually changes from Si3p states to N 2p states.