DC discharge plasma studies for nanostructured carbon CVD

A synthesis of carbon films by d.c. discharge plasma-enhanced chemical vapor deposition using a hydrogen-methane gas mixture was investigated by optical emission spectroscopy and by measurements of current-voltage dependencies. The effects of gas composition and pressure on the characteristics of d.c. discharge in the methane-hydrogen gas mixture are studied. Variation of the deposition process parameters over a wide range allows us to obtain various carbon thin film materials, whose structure and composition were qualitatively characterized by Raman spectroscopy and electron microscopy. The data of optical emission spectroscopy show the presence in the discharge plasma of H, H-2, CH and C-2 activated species, which play a decisive role in nanostructured graphite-like carbon film formation and carbon condensation in the gas phase. We propose a model for the formation of graphitic nanostructured carbon films in plasma containing C-2 dimers. (C) 2003 Elsevier Science B.V. All rights reserved.