Energetics of dopant atoms in subsurface positions of diamond semiconductor

We present a set of ab initio energetics for a substitutional boron (B) impurity atom in subsurface positions, from the topmost to the fifth atomic layer, of both C(001)-2×1:H and C(111)-1×1:H. We compare the calculated surface-B binding energies with those obtained for P [T. Miyazaki, H. Kato, H. Okushi, S. Yamasaki, e-J. Surf. Sci. Nanotech. 4 (2006) 124]. The surface-P binding energies become larger as the position of P is closer to the two surfaces. They are up to ∼4 eV for C(001)-2×1:H and ∼2.6 eV for C(111)-1×1:H, respectively. For B, in contrast, the binding energies are within ∼0.5 eV for both surfaces. An implication of our finding in the context of a mechanism for P and B doping in diamond is discussed.