Multi-wavelength Raman investigation of sputtered a-C film nanostructure

Multi-wavelength Raman spectroscopy is employed to investigate the nanostructure of amorphous carbon (a-C) films, prepared by sputtering at 20 and 400 °C, and the structural modifications produced by thermal anneling at 400 and 800 °C. The results are discussed in the light of more recent assessments on resonant Raman spectroscopy in C-based materials. High-temperature depositions and thermal annealing promote development and/or clustering of sp2 phase, with film optical transparency reduction. In both the cases, nanoclusters of larger and more uniform dimensions are formed at higher temperatures. However, annealing process favours aromaticity, while high-temperature depositions oppositely augments distortions and promotes bond disorder.