Structure of hydrogenated amorphous carbon deposited using saddle-field glow-discharge in methane

Hydrogenated amorphous carbon films (a-C:H) were deposited using the DC saddle-field discharge. The reflectance and transmittance in the visible and UV ranges, infrared absorption, X-ray photoemission spectroscopy (XPS) and Raman spectroscopy were studied. The Tauc energy gap, Urbach energy, sp(2) C=C content, sp(3) C-C content, and C-H bond type and content of the films are presented. The results confirm that the sp(2) sites control the Tauc gap. The change of film structure from wide band gap films to narrow band gap films follows two distinct regimes which are controlled primarily by the ratio of sp(3) C-C to sp(2) C=C bond content. (C) 1999 Elsevier Science B.V. All rights reserved.