Complete characterization by Raman spectroscopy of the structural properties of thin hydrogenated diamond-like carbon films exposed to rapid thermal annealing

Abstract

We have demonstrated that multi-wavelength Raman and photoluminescence spectroscopies are sufficient to completely characterize the structural properties of ultra-thin hydrogenated diamond-like carbon (DLC:H) films subjected to rapid thermal annealing (RTA, 1 s up to 659°C) and to resolve the structural differences between films grown by plasma-enhanced chemical vapor deposition, facing target sputtering and filtered cathodic vacuum arc with minute variations in values of mass density, hydrogen content, and sp3 fraction. In order to distinguish unequivocally between films prepared with different density, thickness, and RTA treatment, a new method for analysis of Raman spectra was invented. This newly developed analysis method consisted of plotting the position of the Raman G band of carbon versus its full width at half maximum. Moreover, we studied the passivation of non-radiative recombination centers during RTA by performing measurements of the increase in photoluminescence in conjunction with the analysis of DLC:H networks simulated by molecular dynamics. The results show that dangling bond passivation is primarily a consequence of thermally-induced sp2 clustering rather than hydrogen diffusion in the film.