Theoretical study of n-type diamond with Li doping and Li-B co-doping: A density functional simulation

The Lithium-doped and Lithium-Boron (Li-B) co-doped diamonds were investigated by density functional theory to find out potential shallow donor impurities in diamond. In Li doped diamond, only interstitial Li doped diamond shows an effective n-type property with a low ionization energy of 0.04 eV. However, an extremely low solubility was found in diamond. In order to overcome this obstacle, co-doping with boron exhibits a unique advantage. A comprehensive research of different Li-B co-doping structures was conducted. With the help of B atom, the solubility of Li is greatly improved. Moreover, through first-principles calculations, we found for the first time that Lii2-B co-doped diamond has both low formation energy (-6.17 eV) and low ionization energy (0.29 eV). The 2p states of B and 2s states of Li dominate the conduction band minimum (CBM). Li atoms have many adsorption sites on intrinsic and B doped (001) surface of diamond, among which the bridge site of the dimer chain is the most suitable adsorption site for Li. It suggests that through the addition of B, Lii2-B co-doping can be an up-and coming candidate of effective shallow donor impurity in diamond.