Progress Toward Atomic Layer Epitaxy of Diamond: Diamond Films Grown One Layer at a Time

Diamond would be the ultimate coating for many applications: it is the hardest material known, is chemically inert in most environments, has a thermal conductivity five times that cooper, and is optically transparent from ultraviolet through the mid- and far-infrared. However, conventional CVD methods for diamond have important limitations-many substrates of interest cannot withstand the 500-1000 degree C temperatures commonly employed, and the typically low nucleation density generates films with large crystal grains and rough morphologies. We are developing a novel low-pressure method for atomic layer epitaxy of diamond which should enable high-quality film growth at modest temperatures with very high nucleation densities. The method uses alternating fluxes of halocarbon radicals and atomic hydrogen, generate by reaction with atomic fluorine. Under suitable conditions carbon atom additions to the growing film and subsequent rehydrogenation of the surface should each be self-limiting reactions, resulting in deposition of one atomic layer of diamond per cycle. To date we have obtained evidence for diamond growth at rates up to 0.1 microns/hr from continuous flows of hydrogen and CHCL3, CH4, or C2H2 at reactor pressures between 10 (exp-4) and 10 (exp-2) Torr