Effect of pressure on the growth of boron and nitrogen doped HFCVD diamond films on WC-Co substrate

Boron and nitrogen compounds are added in the acetone/hydrogen gas mixture to deposit hot filament chemical vapor deposition (HFCVD) diamond films on the cobalt cemented tungsten carbide (WC-Co) substrate under the pressure of 1-4kPa. The as-deposited diamond films are characterized by field emission scanning electron microscope (FESEM), atomic force microscopy (AFM), X-ray diffraction (XRD) spectroscopy and Raman spectroscopy. The results reveal that the surface morphology, growth rate, structure and quality of the diamond films vary with the pressure and the type of the impurity addition. The diamond grains tend to develop into the nanometer scale with the decrease of the pressure. However, adding of boron or nitrogen impurities in the gas mixture will weaken the nanocrystallization effect by reducing the carbon supersaturation. Density functional theory (DFT) calculations indicate that co-adsorption of B and N containing radicals can favor the adsorption of CH3 on diamond (100) surface. Thus, at low pressure of 1kPa, large grained cubic (100) facet diamond rather than typical nanometer diamond is produced for B-N co-addition gas mixture. The present results appear to be useful to efficiently synthesize high quality doped diamonds with desirable properties for mechanical application. Copyright (c) 2015 John Wiley & Sons, Ltd.