The effects of oxygen on diamond synthesis by hot-filament chemical vapor deposition

The effect of oxygen addition on the synthesis of diamond was studied using the hot-filament chemical vapor deposition (HFCVD) method, in which it is simple and easy to control the deposition parameters independently. Diamond films were deposited on silicon wafers under the conditions of substrate temperature 530-950 C, total reaction pressure 700-8000 Pa, and methane concentration 0.4-2.4 percent in both CH4-H2 and CH4-H2-O2 systems. At deposition conditions of low substrate temperature, high CH4 concentration, or high total pressure, soot-like carbon and/or graphite are deposited without oxygen addition. When even a small amount of oxygen (about 0.6 percent) is added, well-faceted diamond films are observed in scanning electron microscopy micrographs and a sharp diamond peak in the Raman spectra appears. The range of deposition parameters for high-quality diamond syntheses are extended by oxygen addition (low substrate temperature, high methane concentration, and high reaction pressure). (Author)