The effects of hydrogenation on the properties of ion beam sputter deposited amorphous carbon

Abstract

The incorporation of hydrogen in ion beam sputtered carbon profoundly affects the physical properties of the amorphous film. Optical absorption, electrical conductivity, and ESR measurements suggest that incorporated hydrogen efficiently passifies the dangling bonds and saturates the graphitic bonding to some extent. By single ion beam sputter deposition, amorphous carbon films containing up to 35 at. % of hydrogen were obtained. This material acts as a narrow band gap (1.2 eV) semiconductor with a relatively low density of states but has an abundance of unsaturated sp2 bonding. In fact, 13C-NMR measurements on this material show that the sp2/sp3 bonding ratio is about 1.5. High density and extreme hardness are properties of ion beam deposited carbon films which contain little or no hydrogen. However, the physical properties of such amorphous carbon which, due to its unique mechanical properties is sometimes referred to as amorphous diamond, are largely dominated by the unsaturated graphitic bonding.