A first-principle study on the electronic properties of substitutionally Cu (I, II)-doped LiNbO3

The electronic properties of Cu-doped lithium niobate (LiNbO3) systems are investigated by first-principles calculations. In this work, we focus on substitutionally Cu[Formula: see text]Li-doped LiNbO3 system with cuprous and cupric doping, which corresponds to the Li[Formula: see text]Cu[Formula: see text]NbO3 and Li[Formula: see text]Cu[Formula: see text]NbO3 [abbreviated as (Li, Cu I)NbO3 and (Li, Cu II)NbO3]. The density functional theory (DFT) calculations show that the electronic property of LiNbO3 is completely different from (Li, Cu I)NbO3 and (Li, Cu II)NbO3. The calculated band structure and density of state (DOS) of (Li, Cu I)NbO3 show a small band gap of 1.34[Formula: see text]eV and the top of valance band (VB) is completely composed of a doping energy level originating from Cu 3d filled orbital. However, the calculated band structure and DOS of (Li, Cu II)NbO3 show a relatively large band gap of 2.22[Formula: see text]eV and the top of VB is mainly composed of Cu 3d unfilled orbital and O 2p orbital.