Study of hydrogenated diamond-like carbon films using x-ray reflectivity

X-ray reflectivity under grazing incidence conditions is a powerful techniq ue to study thin film density, surface roughness, and the multilayer struct ure without destroying the samples. In this article, we, using x-ray reflec tivity technique, have studied the effects of bias voltage and deposition p ressure on the mass density, surface and interface roughness of hydrogenate d diamond-like carbon (DLC) films. It is observed that the surface roughnes s increases with increasing the bias voltage and with decreasing the deposi tion pressure over a wide range. The mass density, hardness and sp(3)/sp(2) ratio deduced from the Raman spectra pass through their maximal values wit h the bias voltage, while they are increased monotonously with the pressure . A thin SiC layer is found to be formed between the DLC films and silicon substrate. According to our results, the influences of the bias voltage and deposition pressure on the film properties are clearly reflected through h ydrocarbon ion energy impinging on the growing surface. Based on the film s urface feature as a function of the ion energy, we suggest that the shallow ion implantation (subplantation) process could be a dominant deposition me chanism. (C) 1999 American Institute of Physics. [S0021-8979(99)06813-9].