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Tetrafluoromethane (CF4) was added to standard CH4/H2 mixtures for diamond 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 was thermally dissociated for filament temperatures over 1800 °C. The observed stable products of its dissociation were mainly C2H2, CH4 and HF. This CF4 addition considerably enhanced the nucleation and growth characteristics on silicon and molybdenum. Diamond growth was observed with substrate temperature as low as 390 °C. A comparative study for the growth dependence on substrate temperature with and without CF4 addition in the gas mixture is presented. The growth rate was measured by post-growth weighing with a micro balance. An activation energy of 11 kcal mol−1 for growth with CF4 addition was obtained. Raman spectra and atomic force microscopy were used to characterize the diamond films.