First-principles calculation to N-type Li[sbnd]N Co-doping and Li doping in diamond

Abstract

The lithium-doped (Li-doped) diamond and lithium‑nitrogen (LiN) 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 LiN 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 LiN4 and LiN3 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 LiN4 is quite low for n-type doping. The N-2s states and Li-s states are responsible for the conduction band edge of LiN4 co-doped diamond. As a result, the LiN4 could be expected as an alternative shallow donor impurity in diamond.