TEM OBSERVATIONS OF DIAMOND FILMS PRODUCED BY HOT FILAMENT THERMAL CVD

Diamond films were provided by a hot filament thermal chemical vapour deposition method with an H2-CH4 gas mixture under various reaction conditions: CH4/H2 ratios of 0.5% and 1.0%, Si and Cu substrates, a substrate temperature of 750-degrees-C, a pressure of 7 torr and a reaction time of 12 h. TEM observation showed that the films produced have many defects such as twins, stacking faults and large distortion of lattices. These defects, which increase with increasing CH4 concentration, seem to be introduced during the crystal growth process. Five-fold symmetry twinned crystals were often observed in the diamond films.