A first-principle study on the electronic properties of substitutionally Cu(Ⅰ,Ⅱ)-doped LiNbO_(3)

摘要

The electronic properties of Cu-doped lithium niobate(LiNbO_(3))systems are investigated by first-principles calculations.In this work,we focus on substitutionally Cu→Li-doped LiNbO_(3) system with cuprous and cupric doping,which corresponds to the Li_(5/6)Cu_(1/6)NbO_(3) and Li_(4/6)Cu_(1/6)NbO_(3)[abbreviated as(Li,Cu Ⅰ)NbO_(3) and(Li,Cu Ⅱ)NbO_(3)].The density functional theory(DFT)calculations show that the electronic property of LiNbO_(3) is completely different from(Li,Cu Ⅰ)NbO_(3) and(Li,Cu Ⅱ)NbO_(3).The calculated band structure and density of state(DOS)of(Li,Cu Ⅰ)NbO_(3) show a small band gap of 1.34 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)NbO_(3) show a relatively large band gap of 2.22 eV and the top of VB is mainly composed of Cu 3d unfilled orbital and O 2p orbital.