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

Abstract The effect of substrate temperature ( T S ) on the microstructure of amorphous nitrogen-substituted carbon thin films (a-C 1− x N x ) has been studied. The a-C 1− x N x 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 T S . 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Csp 2 and CN triple bonding, and suggested the presence of N–Csp 3 bonding in the deposited films. The analysis of the spectra versus T S reveals two rearrangement mechanisms of the microstructure. Up to 150 °C, the reversion of NCsp 2 to N–Csp 3 and CCsp 2 respectively, and the increase the connectivity of the C–C network for higher T S . The Raman features reveals that this progressive graphitisation of the material, with increasing T S , is accompanied by a high disorder form of Csp 2 sites. These results are used to describe the stress variation that accompanies nitrogen evolution within the deposited films.