Consecutive deposition of amorphous SiO2 interlayer and diamond film on graphite by chemical vapor deposition

Chemical vapor deposition (CVD) diamond films can be used as effective protective coatings on graphite components, while the film-substrate adhesion is poor probably due to the graphite etching caused by the atomic hydrogen. It is supposed as a useful way to pre-deposit an amorphous SiO2 (a-SiO2) layer for solving this problem. In this study, by interposing a-SiO2 interlayers, four types of diamond films are deposited on common commercial graphite substrates, and noteworthy is that such the a-SiO2 layer and CVD diamond film are consecutively synthesized in the same hot filament CVD apparatus. It is proved that as-deposited a-SiO2 layer has typical amorphous features, provides sufficient protections on the substrate, and avoids the natural removal of the diamond film when growing. Micro-crystalline diamond, nano-crystalline diamond, boron-doped micro-crystalline diamond (BDMCD) and boron-doped nano-crystalline diamond films deposited on a-SiO2 coated graphite substrates present typical features in consistent with micro- or nano-sized diamond films on other substrates. Among the four diamond films, mainly facing to some application requirements for the electrical conductivity, the BDMCD film shows relatively better comprehensive performance, including high diamond purity, high nano hardness (74.21 GPa) and elastic modulus (890.93 GPa), favorable adhesion and low electrical resistivity (29 mu Omega m). (C) 2017 Elsevier Ltd. All rights reserved.