Electron spectroscopy study of plasma assisted amorphous carbon deposition

Abstract

We report the results of a study of the electronic structure of carbon-based thin films deposited by a RF plasma. A novel cylindrical plasma configuration has been used to grow amorphous hydrogenated carbon films. Electrons within a low pressure, two-temperature plasma are constrained to oscillate between two electrodes and ionize methane/hydrogen mixtures. The ions that form are near room temperature. They drift out of the trap region to deposit on a substrate located beyond the electrodes. The underlying strength of this configuration rests in the ability to control several plasma parameters independently: the flux, energy, and the ratio of the charged to neutral particles leaving the plasma, and the chemical species being deposited. Adjusting these parameters alters the density of the film being grown, its hydrogen content, and the film's porosity and morphology. Films of thickness up to 10 μm have been grown on flat substrates and on cylindrical plastic micro spheres. The electronic structure properties of this material has been studied via X-ray photoemission spectroscopy (XPS) and electron energy loss spectroscopy. The thus-obtained films show primarily a-C:H character.