Hot filament method for growing high purity diamond

Abstract

A method of growing high purity diamond crystallite structures at relatively high growth rates on a temperature resistant substrate, comprising (a) flowing diamond producing feed gases at low pressure through a reaction chamber containing the substrate, the feed gases being comprised of hydrocarbon devoid of methyl group gases, i.e., acetylene or ethylene, diluted by hydrogen, and (b) while concurrently raising the temperature of the substrate to the temperature range of 600.degree.-1000.degree. C., thermally activating the feed gases by use of a hot filament located within the chamber and upstream and adjacent the substrate, the filament being heated to a temperature above 1900.degree. C., that is effective to generate a substantial atomic hydrogen (H) concentration and carbon containing free radicals. A substantial additional loss in carbon balance of the gases is triggered at a lower filament temperature indicative of the formation of intermediate substances that stimulate diamond growth. The gases may be mixed prior to passing the filament and may include CO or equivalent gases to enhance diamond purity. Alternatively, the gases are delivered in a substantially nonmixed condition past said filament and are substantially mixed for the first time at the surface of the substrate.