| Summary: | To better understand the influence mechanism of boron, nitrogen and silicon dopants on the growth of chemical vapor deposition (CVD) diamond film, density functional calculations have been performed to reveal the different impact of the impurities on the CH<sub>3</sub> adsorption on diamond surface. The substituted doping and radical doping of diamond (111) and (100) − 2 × 1 surface are both considered. The calculation results indicate that the CH<sub>3</sub> radicals are hardly adsorbed on nitrogen atoms and thus may cause vacancy in the diamond lattice easily. Boron substituted doping will disfavor the adsorption of CH<sub>3</sub> due to the lacking of valence electron. However, the empty p orbitals of boron atom will help the chemical adsorbing of CH<sub>3</sub> radicals. The substituted silicon doping has little influence on the CH<sub>3</sub> adsorption, as Si atom has the same outer valence electron structure with C atom. In the case of radical doping, the adsorption energy of CH<sub>3</sub> will be reduced due to the steric hindrance between NH<sub>2</sub> or SiH<sub>3</sub> with CH<sub>3.</sub> The adsorption energy can be slightly enhanced when BH<sub>2</sub> radical is pre-adsorbed on diamond (111) surface. However, the BH<sub>2</sub> pre-adsorbed on diamond (100) − 2 × 1 surface may interact with surface radical carbon site and result in a large reduction of CH<sub>3</sub> adsorption energy. Thus, the boron doping may hinder the formation of the (100) facet during the CVD diamond deposition under a certain condition.
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