Dependence of diamond nucleation and growth through graphite etching at different temperatures

Diamond films have been grown on silicon substrate from graphite etching as a carbon source with atomic hydrogen instead of using conventional hydrocarbon in the feed gas. A graphite plate was used as sample support in a hot filament chemical vapor deposition reactor. Graphite temperature demonstrated to have a strong dependence with the diamond nucleation and growth rate. Scanning electron microscopy (SEM) images of graphite targets associated with their Raman spectra were used to analyze their graphite morphology and structural properties before and after etching process for each graphite temperature studied. The results showed that chemical erosion intrinsically induces graphite surface changes that influence Raman spectra. The disorder behavior from the ID/IG ratio presented a maximum value at 900 °C, for 60 min of etching time, when compared with graphite surface at room temperature before atomic hydrogen etching. SEM diamond images were also used to analyze the nucleation rate. Diamonds grown during 15 min at 600 and 700 °C presented the higher nucleation rate. For growth time of 30 min the diamonds are continuous, covering the entire Si substrate surface, with submicrometer grain size. Raman spectra showed good quality diamond coating. Diamond content or diamond purity values, evaluated for growth time of 15, 30 and 60 min increases with the increase of the graphite temperature confirming the high carbon content in the first stage of diamond growth.