Influence of doping on the growth rate of single-crystal diamond fabricated by the HFCVD method

The hot filament chemical vapor deposition (HFCVD) method has the potential to produce single-crystal diamond (SCD) in large quantities with relatively low cost. However, the degree of gas ionization in the HFCVD reaction is lower than that in the microwave plasma environment, resulting in a lower growth rate of SCD. In this study, the density functional theory (DFT) method is used to elucidate the influence mechanism of N-doping and B-doping on the growth rate of SCD. It shows that N-doping can increase the desorption rate of H atoms, providing reaction sites for methyl adsorption. B-doping can directly promote the decomposition of methyl groups and increase their concentration, thereby accelerating the growth rate of SCD. Undoped SCD was fabricated by the HFCVD method using methane and hydrogen as reaction precursors, and N-doped and B-doped SCD were fabricated by adding nitrogen and trimethyl borate vapor as doping precursors. The growth rate and crystal quality of three kinds of SCD were analyzed. Results show that N-doping can increase the growth rate of SCD but reduce the crystal quality of the epitaxial layer. B-doping can maintain single-crystal quality while slightly increasing the growth rate of SCD.