Theoretical Studies of Sulfur and Sulfur-Hydrogen Complexes in Diamond

One of the current understandings of sulfur (S) doping of diamond is described, mainly from a theoretical point of view. First, some published experimental results are introduced. Then, two fundamental problems are defined: 1. whether an isolated substitutional S donor (Ssub) in diamond is shallower than a phosphorus (P) counterpart (Psub), and 2. whether an Ssub has a lower formation energy than a Psub. Recent theoretical (one quantum chemical, and two density-functional (DFT)) studies are reviewed to point out that theoretical results regarding the problems above have not converged yet. Results of the author's DFT calculations are presented for Ssub, and complexes of Ssub with hydrogen (H) as well as other elements such as nitrogen (N), and boron (B), and/or a vacancy. Formation energies of these defects are also presented.