Top-surface characterization of a near frictionless carbon film

A detailed study of the top surface (∼ 2 nm) of a near frictionless carbon film has revealed new information with respect to the sp3 fraction. Previous work on near frictionless carbon films made at Argonne had shown a large fraction of sp2-hybridized carbon in the bulk of the film. However, in this study of the surface, the majority of the carbon was found to be sp3. In addition we compared and contrasted the behavior of the films after mechanical abrasion and Ar+ etching. The study also revealed that oxygen on untreated samples was rapidly reduced by etching or heating or mechanical abrasion; this finding was corroborated by an angle-resolved study, where different depths of the sample were probed. It was also found that the fraction of sp3 carbon decreased linearly with depth, falling in one film from ∼ 90% sp3 to ∼ 80% sp3 in the top 2 nm.