Annealing effects on the microstructure of amorphous carbon nitride films

Amorphous carbon nitride films, prepared using a dc facing-target reactive sputtering system, were annealed at temperatures up to 650 8C for 1 h in vacuum. The effects of heat treatment on the films, i.e. changes in the composition and structure, were investigated. It was found that annealing at temperatures ranging from 300 to 650 8C, results in the N content decreasing from 33 at.% in the as-deposited films to 5 at.%. The loss of N, especially those bonded to sp3C, causes the rearrangement of the film’s microstructure, and the dual effects of the thermal annealing are quite noticeable: (1) annealing destroys most graphite-like structures, and more non-aromatic sp2C components and C N terminal structures are formed at higher annealing temperatures, contributing to a looser film’s structure. (2) Annealing makes the remaining aromatic sp2C structure become more order. The results also reveal that N atoms bonded to sp3C are easily removed with the increasing temperature compared to those bonded to sp2C, which indicates that N–sp2C bonds had a higher thermal stability than N–sp3C.