THE ROLE OF H2O IN ENHANCING HOT-FILAMENT ASSISTED DIAMOND GROWTH AT LOW-TEMPERATURES

The addition of a small amount of oxygen to a hot filament assisted ch emical vapor deposition reactor allows diamond to be deposited at sign ificantly lower filament and substrate temperatures. Scanning electron microscopy and Raman spectroscopy are used to compare films grown wit h and without oxygen addition as a function of substrate temperature a t high and low filament temperatures. Oxygen addition is found to favo r growth of high quality diamond at low substrate temperatures (<600 d egrees C). The amount of nondiamond carbon is reduced and the clarity and smoothness of facets improves dramatically under these conditions. Equilibrium calculations and residual gas analysis indicate there is H2O in the gas above the substrate during these depositions. The corre lation between the dramatic reduction in the nondiamond carbon content of the films and the increased H2O levels near the substrate at low t emperatures leads to the conclusion that H2O plays an important role i n facilitating deposition at lower temperatures. Potential roles for H 2O include terminating carbon dangling bonds by dissociative adsorptio n and enhancing selective etching of nondiamond carbon by O-2. The gas and surface chemistry of diamond deposition at low temperatures with oxygen addition is also discussed. (C) 1997 American Institute of Phys ics.