HOMOEPITAXIAL GROWTH OF DIAMOND BY AN ADVANCED HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION METHOD

Homoepitaxial (111), (110), and (100) diamond films were grown by an a dvanced hot-filament chemical vapor deposition method that enables acc urate control of the substrate temperature independently of the other chemical vapor deposition parameters. The obtained films were examined mainly by optical microscopy and reflection high energy electron diff raction (RHEED). The surface morphology of the films depended on the d eposition pressure, methane concentration in the feed gas, and substra te temperature. Very streaky RHEED patterns, indicative of atomically smooth surfaces, were obtained from the samples deposited on the (111) substrates at a pressure of 100-500 Torr and methane concentration of 0.5%, and also from the samples deposited on the (100) substrates at 300-500 Torr and 1%-2%. These conditions, which we call ''window'' con ditions, are remarkable, since such deposition pressures as 100-500 To rr are much higher than the few tens of Torr normally required for pol ycrystalline growth. However, the films on the (110) substrates exhibi ted spotty patterns due to three-dimensional growth, although optical microscopically smoothness was achieved by the 500 Torr and 0.5% depos ition. Regarding the pressure effects, a reduction of H radicals and c oncurrent increase of the C2Hx(x = 1-2) species are characteristic of the gas-phase chemistry under these window conditions. We speculate th at the success of epitaxial deposition under these window conditions w as due to surface reconstruction arising from the lack of H radicals a nd/or from the surface reactions in which C2Hx mediates.