RAMAN-SCATTERING FROM HYDROGENATED AMORPHOUS-CARBON

The changes in the atomic structure as a function of annealing tempera ture have been studied by Raman scattering in two different series of hydrogenated amorphous carbon (a-C:H) deposited in a D.C. multipolar p lasma system from methane gas. Series I and II samples were obtained a t substrate biases respectively equal to -40 V and -600 V. In the as-d eposited state, the two series have completely different microstructur es (sp(2):sp(3) ratio). Indeed, the Raman spectra obtained for samples of series II show two peaks; a broad one situated around 1360 cm(-1), and a more intense peak centred at about 1580 cm(-1). On the contrary , the Raman spectra of the as-deposited samples of series I are concea led by the photoluminescence band. For low annealing temperatures (T < 500 degrees C), the two series behave differently and still exhibit c ompletely different structure. For high temperatures (T > 500 degrees C), the samples of the two series converge to a similar structure, clo se to that of polycristalline graphite.