LOW-TEMPERATURE GROWTH OF DIAMOND FILMS BY MICROWAVE PLASMA CHEMICAL-VAPOR-DEPOSITION USING CH4+CO2 GAS-MIXTURES

Abstract

Diamond films were deposited on Si substrates at low temperatures using CH4 + CO2 gas mixtures, which are different from conventional mixtures such as CH4 + H-2, CH4 + O2 + H-2 and CO + O2 + H-2. The films were deposited by microwave plasma chemical vapor deposition. High quality diamond films with high growth rates were fabricated at lower temperatures than those used by previous researchers. After 24 h of deposition, the deposited films were characterized using scanning electron microscopy, and their quality was determined by laser Raman spectroscopy and X-ray diffraction. The results showed that, when the microwave power was set at 290 W, well-faceted diamond films were formed in the total gas pressure range 6-25 Torr. The substrate temperatures and the volume ratios [CH4]/[CO2] (in volume per cent) were also changed from 340 to 220-degrees-C and from 60.1 % to 57.3% respectively. The growth rate of diamond films changed from 0.31 to 0.18 mum h-1 in the above growth temperature range. The growth rate of the diamond films increased as the substrate temperature increased. Consequently, we predict that diamond films may be formed using CH4 + CO2 gas mixtures, even at temperatures of less than 200-degrees-C.