Influence of argon gas pressure on the ZnO:Al films deposited on flexible TPT substrates at room temperature by magnetron sputtering

Abstract

Aluminium doped ZnO thin films(ZnO:Al) were deposited on transparent polymer substrates at room temperature by rf magnetron sputtering method from a ZnO target with Al2O3 of 2.0 wt%. Argon gas pressure varied from 0.5 Pa to 2.5 Pa with radio frequency power of 120 W. XRD results showed that all the ZnO:Al films had a polycrystalline hexagonal structure and a (002) preferred orientation with the c-axis perpendicular to the substrate. The grain sizes of the films were 6.3–14.8 nm.SEM images indicated the ZnO:Al film with low Argon gas pressure was denser and the deposition rate of the films depended strongly on the Argon gas pressure, increasing firstly and then decreasing with increasing the pressure. The highest deposition rate was 5.2 nm/min at 1 Pa. The optical transmittance of the ZnO:Al films increased and the blue shift of the absorption edge appeared when the Argon gas pressure increased. The highest transmittance of obtained ZnO:Al films at 2.5 Pa was about 85% in the visible region. The electrical properties of the films were worsened with the increase of the Argon gas power from 1 Pa to 2.5 Pa. The resistivity of obtained film at 1.0 Pa was 2.79 ×10−2 Ω·cm.