First-Principles Studies of Ti-Related Defects in Diamond

The transition metal-related centers of diamond exhibit good properties. Herein, a first-principles method based on density functional theory (DFT) is used to study single-doped Ti-related point defect structures and codoped structures of Ti and B or N, which possibly exist in diamond; the electronic structure and formation energy are also calculated. The results from structural calculations show that Ti is more likely to be located adjacent to a vacancy to form a TiV structure, which is more stable than other configurations. Ti doping introduces impurity levels into the pure diamond band gap, and the possible energy level transitions are determined. The results from the calculations of the codoped system show that the incorporation of N or B atoms is beneficial for the formation of defect structures and that the incorporation of N optimizes the energy band structure of the defects. When a substitutional Ti atom is located adjacent to a B atom and forms a Ti-B structure, and when four N atoms replace the corresponding neighboring C atoms around TiV to form a TiV-4N structure (which is similar to the NE8 configuration), the structure shows a better energy band structure, which presents new color centers.