Structural and physical characteristics of ultrananocrystalline diamond/hydrogenated amorphous carbon composite films deposited using a coaxial arc plasma gun

Ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) films were formed without initial nucleation using a coaxial arc plasma gun. The UNCD crystallite diameters estimated from the X-ray diffraction peaks were approximately 2nm. The Fourier transform infrared absorption spectrum exhibited an intense sp³-CH peak that might originate from the grain boundaries between UNCD crystallites whose dangling bonds are terminated with hydrogen atoms. A narrow sp³ peak in the photoemission spectrum implied that the film comprises a large number of UNCD crystallites. Large optical absorption coefficients at photon energies larger than 3eV that might be due to the grain boundaries are specific to the UNCD/a-C:H films.