Spectroscopic investigations of the microstructure changes induced by substrate temperature in nitrogen-substituted amorphous carbon thin films Original Research Article

The effect of substrate temperature (TS) on the microstructure of amorphous nitrogen-substituted carbon thin films (a-C1−xNx) has been studied. The a-C1−xNx films were deposited on Si(1 0 0) using reactive radio-frequency (RF) magnetron sputtering of a high-purity graphite target in a pure nitrogen plasma using different RF powers and different substrate temperatures TS. Combined Fourier transform infrared (FTIR), Raman spectroscopy and residual stress measurements are used to fully characterise the films in the as-deposited state. FTIR spectra showed the existence of NCsp2 and CN triple bonding, and suggested the presence of N–Csp3 bonding in the deposited films. The analysis of the spectra versus TS reveals two rearrangement mechanisms of the microstructure. Up to 150 °C, the reversion of NCsp2 to N–Csp3 and CCsp2respectively, and the increase the connectivity of the C–C network for higher TS. The Raman features reveals that this progressive graphitisation of the material, with increasing TS, is accompanied by a high disorder form of Csp2 sites. These results are used to describe the stress variation that accompanies nitrogen evolution within the deposited films.