THE EFFECTS OF OXYGEN ON DIAMOND SYNTHESIS BY HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

Abstract

The effects of oxygen addition on the synthesis of diamond are extensively studied by using the hot-filament chemical vapor deposition (HFCVD) method, in which it is simple and easy to control the deposition parameters independently. Diamond films are deposited on silicon wafers under the conditions of substrate temperature 530-950-degrees-C; total reaction pressure 700-8000 Pa; and methane concentration 0.4-2.4% 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%) 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).