Native defects in LiTaO3 photocatalyst : a DFT study

Abstract

First principle calculations based on density-functional theory were conducted to investigate the formation energies of various native defects in lithium tantalate, LiTaO3, a prospective photo catalyst for the splitting of water. The formation of various defects is found to be sensitive to the growth conditions that LiTaO3 is subjected to. Vacancy defects formation is easier (difficult) when corresponding element concentration is poor (rich). The element rich condition also promotes the formation of corresponding interstitial defects. Cation antisite defects (LiTa and TaLi) are more easily formed at Li-rich & Ta-poor and Ta-rich & Li-poor conditions. VLi-, VTa5- and LiTa4- are deep acceptors whereas VO2+, TaLi4+, ILi+ and ITa5+ are shallow donors. TaLi4+ is found to be the most stable defect species in all growth conditions. VLi is stable at Li-poor and O-rich condition whereas VTa and LiTa are stable at O-rich and Ta poor conditions. At O-rich & Li-poor and O-poor & metal (Li and Ta) rich conditions, LiTaO3 is a very good n-type semiconductor and has high carrier electrons concentration. These results agree well with experimental findings.