Effect of metal coating on the formation of diamond whiskers in O2 RF plasma

As-grown and metal-coated CVD diamond films were etched in an O2 radio-frequency plasma. In this study, Molybdenum (oxidizable) and Nickel (non-oxidizable) were used as coating materials. The distribution of the whiskers was investigated and compared. In the case of as-grown diamond film, the whiskers were found preferentially formed at the diamond grain boundaries. The metal-coated diamond films were distinctly influenced by the oxidizability of the coating metal. Under the same etching condition, lower density whiskers (10 μm− 2) were obtained from the Mo-coated diamond film, and in this case the whiskers were about 50 nm in diameter and 200 nm in height. However, the peak intensities of the whiskers measured by cathodoluminescence remained the same as those of the non-etched diamond films. Compared to the Mo-coated film, whiskers obtained from the Ni-coated film were more densely distributed (40 μm− 2); also, their quality deteriorated with the etching, as did their cathodoluminescence peak intensities. In both cases, the properties of bonding structures were compared before and after etching. It was found that the whiskers kept the sp3 diamond bonding structure even after etching.