Analysis of the behaviour of SnO2 composites of ZnO and TiO2 using impedance spectroscopy

Abstract

Composite semiconductor nanostructures will contribute in large measure for the future generation of cost effective optoelectronic devices. In order to advance the progress it is important to understand the mechanism of charge injection, transport and recombination in these systems. Impedance spectroscopy (IS) is a relatively old and powerful method for characterizing many of the electrical properties of materials and their interfaces. In this study, the impedance of composite porous films of SnO 2 /ZnO and SnO 2 /TiO 2 have been taken into consideration and their behaviour in composite films was analyzed using IS to describe the mechanism of charge carrier transportation. The composites of SnO 2 and ZnO showed higher resistivity than their pure form and when SnO 2 : ZnO is in 1:1 ratio the resistivity of the composite film was the lowest (7.6 × 10 4 kΩ m). When the percentage of SnO 2 is around 40 % and 90 % the resistivity of the films were higher where each of these cases could be explained by the depletion of electrons in the conduction band of SnO 2 and ZnO at the interface. In contrast to the SnO 2 and ZnO composite films, the minimum resistivity of 5.86 × 10 5 Ωm was obtained for SnO 2 and TiO 2 composite films when SnO 2 is 33 %, which is lower than when they are in pure form. This low resistivity of both composite films is possibly attributed to the formation of a super structure in the composites where the electrons transport ballistically in mini bands.