Sulfur: A potential donor in diamond

We performed first-principle calculations of substitutional sulfur in diamond, in the neutral $({\mathrm{S}}^{\mathrm{0}})$ and charged states. The energy levels induced by sulfur in diamond are calculated to be 0.15 and 0.5 eV from the bottom of the conduction band, for ${\mathrm{S}}^{\mathrm{0}}$ and the singly ionized state ${\mathrm{S}}^{\mathrm{+}},$ respectively. The formation energy for the neutral state of sulfur is found to be 7.2 eV, lower than that of phosphorus in diamond. The most likely state of sulfur in diamond is found to be the doubly ionized state ${\mathrm{S}}^{\mathrm{++}},$ which cannot act as a donor. However, a small fraction of sulfur can be found in the singly ionized state ${\mathrm{S}}^{\mathrm{+}},$ which can donate an electron for conduction at reasonable temperatures.