First-principles calculation to N-type li N co-doping and li doping in diamond

Abstract The lithium-doped (Li-doped) diamond and lithium‑nitrogen (Li N) co-doped diamond at different structures were investigated by the first-principles density functional theory to explore the possibility to achieve effective and shallow donors in diamond. Although the ionization energy of interstitial Li-doped diamond is low, its high formation energy shows that Li could be insoluble in diamond. However, the formation energy of Li N co-doped diamond decreases with increasing the number of N atoms around the Li atom. We found, for the first time, the formation energies of Li N4 and Li N3 co-doped diamond are negative, indicating that the doping efficiency of Li in diamond could be improved by introducing N atoms. Furthermore, we demonstrated that the ionization energy of Li N4 is quite low for n-type doping. The N-2 s states and Li-s states are responsible for the conduction band edge of Li N4 co-doped diamond. As a result, the Li N4 could be expected as an alternative shallow donor impurity in diamond.