Sn doping effects on properties of ZnO thin films deposited by RF magnetron sputtering using a powder target

Abstract

In the present study, tin doped ZnO thin films (ZnO:Sn) at different contents (0–3 wt%) were deposited onto glass substrates by RF magnetron sputtering using a powder compacted target at room temperature. The effect of Sn concentration on the structural, optical and electrical properties of the ZnO:Sn thin films were investigated. The X-ray diffraction analysis shows that the pure ZnO thin film exhibits a strong intensity of the (002) peak indicating a preferential orientation along the c-axis. For Sn doped ZnO thin films, there is a change in the orientation from the (002) plane to the (101) one. The undoped ZnO thin films have transmittance 85% in the visible range and slightly increased for 0.5 wt% of Sn, while it get decreased with further increasing the Sn doping concentration. The optical band gap energy get increased with increasing the doping concentration. Moreover, the electrical conductivity and conduction mechanism are also studied by impedance spectroscopy in the frequency range of 1KHz–13 MHz at various temperatures (633–743 K). The AC conductivity in ZnO thin films increased with angular frequency. The frequency exponent S decreases with increasing temperature. Such behavior suggests that the correlated barrier hopping (CBH) model may be suitable to explain the conduction mechanism in ZnO thin films. The activation energy values calculated from angular frequency and DC conductivity are in good agreement confirming that the conduction mechanism is thermally activated by hopping between localized states.