Study on Defects in Ultrananocrystalline Diamond/Amorphous Carbon Composite Films Prepared by Physical Vapor Deposition

Abstract

Ultrananocrystalline diamond/amorphous carbon composite (UNCD/a-C:H) films was deposited by coaxial arc plasma deposition with a graphite target. UNCD/a-C:H films prepared by physical vapor deposition show large optical absorption coefficients in the photon range from 3 to 5 eV due to disordered structures in a-C:H and grain boundaries. Electron spin resonance measurement indicates the existence of a large number of dangling bonds with a density of ~1022 cm−3. These dangling bonds might cause the formation of localized states in diamond band gap and contribute to the optical absorption properties specific to the UNCD/a-C:H films.