Role of Si as carrier suppressor in amorphous Zn-Sn-O

Through the first-principles study, we investigated the microscopic properties of oxygen vacancy in the amorphous Zn2SnO4 (a-ZTO) and the amorphous Si-doped Zn2SnO4 (a-SZTO). The oxygen vacancy (V(O)) is found to play a role of shallow donor as sources of n-type conductivity in the both a-ZTO and a-SZTO. In both materials, V(O) is preferred to couple with Sn, and the coordination number (CN) of Sn is overall reduced by O-deficiency. However, an interesting finding is that in the presence of Si, the formation of V(O) can be significantly suppressed, and the formation enthalpy is calculated to be increased. The computational results suggest that Si atom can be an excellent carrier suppressor in a-ZTO. We also find that the effective mass of electron carrier is increased in the presence of Si. These results can be explained in the respect of the overall decrease of the oxygen coordination numbers of Sn atoms by the strain effect induced by Si. (c) 2012 Elsevier B.V. All rights reserved.