Structural and electronic properties of Sb-doped SnO2 (1 1 0) surface: A first principles study

Abstract

The structural and electronic properties of stoichiometric and Sb-doped SnO2 (110) surfaces have been investigated using effective core pseudopotential (ECP) first-principle approach in the density functional theory at the B3LYP level. The supercells Sn48−2nO96Sb2n in which n=2, 3, 4 and 5 with symmetric and homogeneous distribution of Sb were employed to adjust the atomic Sb/Sn ratio in Sb-doped SnO2 (110) surfaces over a range of atomic Sb/Sn ratio from 9.09 to 26.31% which are closed to experimental values of the Sb doped SnO2. We find that substitution of Sb for Sn yields significant structural relaxation and modification of the charge around Sb in Sb-doped SnO2 (110) surfaces, resulting in very large displacements of five-fold Sb compared to that of Sn atoms in stoichiometric SnO2 (110) surface. Sb doping introduces occupied surface states of hybridized 5s and 5p orbitals of Sb atoms at the high energy side of the top of the valence band (VB) within the band gap, and they contribute to the band gap narrowing from 2.82eV to 2.33eV. It is found that the Sb substituted for Sn at the surface acts as donor as well as acceptor centers. The role of Sb in improving the surface conductivity of Sb-doped SnO2 (110) surfaces is discussed and compared to that reported in literature for Sb-doped SnO2 bulk and nanostructure.