DIAMOND GROWTH WITH CF4 ADDITION IN HOT-FILAMENT CHEMICAL-VAPOR-DEPOSITION

Tetrafluoromethane (CF4) was added to standard CH4/H-2 mixtures for di amond growth in hot-filament-assisted chemical vapour deposition. CF4 concentrations in the range of 0.3%-3% were studied. Mass spectrometry of the exhaust gas showed that only a small fraction (<15%) of CF4 wa s thermally dissociated for filament temperatures over 1800 degrees C. The observed stable products of its dissociation were mainly C2H2, CH 4 and HF. This CF4 addition considerably enhanced the nucleation and g rowth characteristics on silicon and molybdenum. Diamond growth was ob served with substrate temperature as low as 390 degrees C. A comparati ve study for the growth dependence on substrate temperature with and w ithout CF4 addition in the gas mixture is presented. The growth rate w as measured by post-growth weighing with a micro balance. An activatio n energy of 11 kcal mol(-1) for growth with CF4 addition was obtained. Raman spectra and atomic force microscopy were used to characterize t he diamond films.