Inhomogeneous carbon bonding in hydrogenated amorphous carbon films

Abstract

Hard-carbon films prepared by the rf-plasma decomposition of acetylene have been investigated by high-resolution 13C nuclear magnetic resonance spectroscopy, x-ray photoelectron spectroscopy (XPS), and the H( 15Nα,γ)C nuclear resonant reaction. It was found that the ratio of sp2:sp3 bound carbon was 1.6, and that virtually all sp3 carbon atoms are, in fact, bound to one or more hydrogen atoms. Bulk layers contain about 40% hydrogen; however, results of the measurements of the hydrogen concentration, as well as those of XPS, confirm that the composition and properties of these carbon films are a strong function of their distance from the initial growth interface, and are spatially varying over the first 40 nm.