Effects of Ti doping at the reduced SnO2(110) surface with different oxygen vacancies: a first principles study

Abstract

A series of Ti-doped SnO2(110) surfaces with different oxygen vacancies have been investigated by means of first principles DFT calculations combined with a slab model. Three kinds of defective SnO2(110) surfaces are considered, including the formations of bridging oxygen (O b ) vacancy, in-plane oxygen (O i ) vacancy, and the coexistence of O b and O i vacancies. Our results indicate that Ti dopant prefers the fivefold-coordinated Sn site on the top layer for the surface with O b or O i vacancy, while the replacement of sublayer Sn atom becomes the most energetically favorable structure if the O b and O i vacancies are presented simultaneously. Based on analyzing the band structure of the most stable configuration, the presence of Ti leads to the variation of the band gap state, which is different for three defective SnO2(110) surfaces. For the surface with O b or O i vacancy, the component of the defect state is modified, and the reaction activity of the corresponding surface is enhanced. Hence, the sensing performance of SnO2 may be improved after introducing Ti dopant. However, for the third kind of reduced surface with the coexistence of O b and O i vacancies, the sublayer doping has little influence on the defect state, and only in this case, the Ti doping state partly appears in the band gap of SnO2(110) surface.