Influence of target-to-substrate distance on the properties of AZO films grown by RF magnetron sputtering

Abstract

Transparent conductive aluminum-doped ZnO (AZO) films were prepared by RF magnetron sputtering on glass substrates with specifically designed ZnO target using high-purity of zinc oxide (99.99%) and aluminum hydroxide (99.99%) powders. Systematic study on dependence of target-to-substrate distance ( D ts) on structural, electrical and optical properties of the as-grown AZO films was mainly investigated in this work. XRD shows that highly preferred AZO crystal in the [001] direction was grown in parallel to the substrate while the D ts doesnot effected to the peak position of XRD. With decreasing D ts the growth rate is increased while the electrical resistivity as well as crystal size in the AZO films is decreased. The XPS data show that zinc has remained with nearly oxidation state and has been attributed to the presence of excess zinc in the films. The O/Zn ratio in AZO films was increased with increasing D ts in the films. The as-grown AZO films have an average transmittance of above 85% at the visible region. The optical band gap of the as-grown AZO films was changed from 3.18 to 3.36 eV with D ts. The resistivity of the film deposited under D ts of 45 mm with 4 wt.% Al(OH) 3 doped ZnO in target was approximately 9.8×10 −2 Ω cm, showing a semiconductor property.