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 sad dle-field discharge. The reflectance and transmittance in the visible and U V ranges, infrared absorption, X-ray photoemission spectroscopy (XPS) and R aman 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 a re 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 ra tio of sp(3) C-C to sp(2) C=C bond content. (C) 1999 Elsevier Science B.V. All rights reserved.