Codeposition of amorphous zinc tin oxide using high power impulse magnetron sputtering: characterisation and doping

摘要

Thin film zinc tin oxide (ZTO) has been energetically deposited at 100 degrees C using high power impulse magnetron sputtering (HiPIMS). Reactive co-deposition from Zn (HiPIMS mode) and Sn (DC magnetron sputtering mode) targets yielded a gradient in the Zn: Sn ratio across a 4-inch diameter sapphire substrate. The electrical and optical properties of the film were studied as a function of composition. As-deposited, the films were amorphous, transparent and semiinsulating. Hydrogen was introduced by post-deposition annealing (1 h, 500 degrees C, 100 mTorr H-2) and resulted in significantly increased conductivity with no measurable structural alterations. After annealing, Hall effect measurements revealed n-type carrier concentrations of similar to 1. x. 10(17) cm(-3) and mobilities of up to 13 cm(2) V-1 s(-1). These characteristics are suitable for device applications and proved stable. X-ray photoelectron spectroscopy was used to explore the valence band structure and to show that downward surface band-bending resulted from OH attachment. The results suggest that HiPIMS can produce dense, high quality amorphous ZTO suitable for applications including transparent thin film transistors.