CONTROL OF SUBSTRATE-TEMPERATURE DURING DIAMOND DEPOSITION

A method is reported for controlling substrate temperature during chem ical vapor deposition of diamond in high heat flux environments such a s thermal plasmas or flames. The method is based on flowing a variable -composition argon-helium mixture through channels between the substra te and a water-cooled base. A fiberoptic pyrometer temperature reading from the back of the substrate provides feedback for active substrate temperature control. Experiments in an atmospheric-pressure RF reacto r under diamond growth conditions indicated that substrate temperature could be sensitively varied by over 600 K by varying the composition of the argon-helium mixture. The effect is explained in terms of the v ariable thermal contact resistance at the interface between the substr ate and the base.