Deposition of ultrananocrystalline diamond at low temperature using CO, CH4 mixed carbon source

Abstract

UNCD (Ultrananocrystalline diamond) is a material with various excellent properties, but the high deposition temperature limits its application. UNCD was deposited at low temperature (700 K) using CO–CH4–H2-Ar as gas source. CO as reaction gas reduces the activation energy of CH4 system. The effects of different H2 concentrations on the morphology of diamond films were studied. The results show that ultra-nanocrystalline films can be deposited by CO–CH4–H2-Ar. The morphology of UNCD film can be observed by SEM images from dense film to needle film and then to spherical clusters. With the increase of H2 concentration, sp2 content decreased, and a-C:H appeared, and a-C:H increased first and then decreased. Analysis of OES(optical emission spectra) showed that the content of C2 under mixed carbon source was higher than that of single carbon source, and the change of CH390 was related to the formation of a-C:H. The optical properties of the film were tested, and the maximum transmittance was 88.9%.