EFFECT OF SUBSTRATE-TEMPERATURE DISTRIBUTION ON THERMAL PLASMA-JET CVD OF DIAMOND

A technique based on a proper substrate holder design and a method for substrate attachment were developed for thermal plasma jet chemical vapor deposition of diamond over larger areas. Non-uniform cooling across the substrate was matched to the highly non-uniform heat flux in the impinging plasma jet, resulting in an almost uniform temperature distribution at the substrate surface (the ratio of the plasma jet diameter to the substrate diameter is about 0.2). The performance of optical pyrometers was evaluated under diamond deposition conditions, ensuring reliable measurements of the substrate temperature. Diamond films of 35 mm diameter were obtained with an average growth rate of 100 mum h-1. Free-standing films were semitransparent. Preliminary results indicated the importance of species and fluid boundary layers on the surface morphology and the film density for given deposition conditions.