Insight into B-S ratio model and surface atom interactions of co-doping diamond: First-principles studies

The complex co-doping structure of boron and sulfur is investigated using the density functional theory approach. Different ratio models show significant differences in electronic properties. More importantly, the interactions of boron, sulfur, and carbon atoms are studied on intrinsic/B-doped (001), (111), and (110) diamond surfaces. The most stable adsorption site, adsorption structure, and charge transfer are discussed. B atom induces a larger adsorption energy (intrinsic:-4.57 eV,-4.56 eV, and-4.00 eV; B-doped:-4.70 eV,-4.72 eV, and-4.86 eV). And a larger charge transfer between diamond and S radicals is also found. Therefore, the phe-nomenon that the sulfur contents in diamond increases after the introduction of boron in the experiment can be explained. Considering different crystal surfaces, larger adsorption strength is obtained from (111) and (110) surface. And different levels of strain are introduced into three different surfaces. The migration barrier of S atom is also considered. The lowest migration barrier is 0.06 eV on (111) surface, whereas the highest value is found on (001) surface (1.96 eV). B atom also benefits for the HxS radical adsorption. It can be concluded that B doping can help with S and HxS adsorption. This study can provide an explanation for the increased solubility of S on B-doped diamond.