Effect of gas composition on the growth and electrical properties of boron-doped diamond films

Boron-doped diamond films are synthesized by the hot-filament chemical vapor deposition (HFCVD) method via introduction of the gas mixtures of methane and hydrogen, as well as the boron precursor carried by H2 through a B(OCH3)3 liquid, into the chamber. Boron-doping level in as-grown diamond films can be well controlled in the range from 1019 to 1021 cm− 3 by adjusting the B/C ratios of gas mixtures. The morphology, structure and resistivity of as-grown diamond films are investigated with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Hall measurement system. The results show that the crystal quality and carrier concentration and resistivity of the as-grown films are obviously dependent on the B/C ratio of the gas mixtures during the deposition process. A critical B/C ratio of 3:4 is found to correspond to the highest crystal quality, highest carrier concentration and smallest film resistivity of as-grown boron-doped diamond films, which should be mainly related with the effective doping ability. In addition, based on the growth kinetics of the diamond films, the effect of the boron-doping on the growth process is discussed in detail.