Conduction-type control of SnSx films prepared by the sol-gel method for different sulfur contents

The effect of S content on the electrical property of the sol-gel SnSx films was examined. The observed conduction-type changes are related to the different ratios between the concentrations of Sn4+ and Sn2+. The experimental identification confirms that n-type conversion is due to an increase in the atomic concentration ratio of Sn4+/(Sn4+ + Sn2+) in the S-rich film. The probability of having formed Sn vacancies (V-Sn) should be high under S-rich growth conditions. Transformation from V-Sn to V-Sn(2) is accompanied by lattice relaxation. Therefore, transformation from Sn2+ to Sn4+ is an offset to lattice relaxation under S-rich growth conditions, increasing the electron density and producing n-type conversion. A suitable sulfur concentration is an important issue for tuning conduction type of SnSx. (C) 2012 Elsevier B. V. All rights reserved.