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

Abstract

A series of Ti-doped SnO 2 (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 SnO 2 (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 SnO 2 (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 SnO 2 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 SnO 2 (110) surface.

Ab initio thermodynamic study of the SnO2(110) surface in an O2 and NO environment: a fundamental understanding of the gas sensing mechanism for NO and NO2

“…[3][4][5][6][7][8][9][10][11] In all these applications, the key for governing device functionality is the properties of the SnO 2 surface or its interface with functional organic molecules. Moreover, the optical, electronic and catalytic properties of SnO 2 depend critically on surface modifications such as impurities, defects or adsorbates, [12][13][14][15][16] and especially, its electric conductivity varies sensitively upon adsorption of the gas molecule at the surface. 17,18 Such a conductance change in the sensing layer was well established to be the basic detection principle of a chemical gas sensor, and yet a fundamental understanding of the key phenomena at the SnO 2 surface remains debatable.…”