Synthetic pathway of shallow n-type donor: Theoretical study of Li and B co-doped diamonds

Abstract

To find potential n-type diamonds with shallow donor energy levels and low formation energies, the thermodynamic and electronic properties of Lithium-Boron (LiB) co-doped diamonds have been investigated using density functional theory (DFT) and hybrid density functional theory (HSE06). The structure, formation energy, electronic property and the potential synthesis pathway are analyzed. The results of the single Li defect is not a suitable candidate for a shallow n-type donor, as it distorts the diamond lattice and forms clusters, in agreement with previous work. The calculated ionization energy of Lii2-B defect (0.29 eV) and the impurities formation energy (0.196 eV) is much lower than that of Lii defect. It suggests that the introduction of B helps improve the solubility of Li in diamond. Further structural analysis has shown that the incorporation of B atoms inhibits the diffusion of Li atoms and simultaneously reduces the internal strain in the diamond, resulting in a significant reduction in the distance between the two lithium atoms from 2.061 Å to 1.629 Å. At last, a non-molecular synthesis pathway of Lii2-B co-doped diamond is proposed via prior generation of B-doped diamond at which Li atom is mobile which indicates there is a potential window-of-opportunity to prepare Lii2-B co-doped diamond to achieve n-type diamond.