Theoretical study on the formation of diamond germanium vacancy color center

Abstract Germanium-vacancy (GeV) color centers in diamond are superior to other color centers in terms of luminescence intensity. The Ge-doping process is key to the successful preparation of GeV color centers in diamond. In this study, the formation mechanism of GeV color centers is explored via first-principles calculations of the adsorption and migration of Ge on the (001) surface of diamond. The results reveal that Ge atoms on the surface of completely hydrogenated diamond have a negative adsorption energy, indicating that they cannot be adsorbed. In contrast, the adsorption energy of Ge atoms on the surface of non-perhydrogenated diamond is relatively large, which indicates that the surface of non-perhydrogenated diamond can adsorb Ge atoms. When Ge atoms are closer to hydrogen defects, their adsorption energy is greater. As the extent of hydrogen deficiency increases, the overall adsorption energy increases accordingly. The hydrogen deficiency of the diamond surface may determine the extent of the Ge content on the diamond surface. Magnetic moment, differential charge, and Bader analyses reveal that charge is transferred between Ge and carbon atoms on the diamond surface. In addition, the Ge and carbon atoms form covalent bonds at positions where the adsorption energy is maximum. Finally, the migration of Ge atoms on the diamond surface enables them to reach a stable position easily.