Diamond nucleation on unscratched SiO2 substrates

Abstract

Enhanced diamond nucleation on fused silica was obtained by using chemical surface pretreatments, instead of prescratching the surface with diamond or another abrasive. One approach was to deposit a thin metal film on the SiO2 substrate. This made it possible to apply a dc bias and obtain significant nucleation during microwave-assisted chemical-vapor deposition. On uncoated silica substrates (i.e., a metal film was not applied), we used a pretreatment step at a lower temperature and lower microwave power to enhance nucleation. The same pretreatment was applied to Si and Mo coated SiO2 substrates, and significant diamond nucleation did not occur. This suggests that the SiO2 substrate is more favorable for nucleation (under these conditions), or that the oxide substrate alters the local plasma chemistry in a way that enhances nucleation.