Optimization of Sputtered AZO Thin Films for Device Application

Abstract

Transparent conducting aluminium doped zinc oxide (AZO) thin films have attracted much attention for wider application in thin film devices such as thin film transistors, solar cells, gas sensors, piezoelectric transducers, etc. owing to their good electrical and optical properties combined with wide energy gap, non-toxicity, good stability and low cost in comparison to the ITO. The AZO thin films have been deposited by DC magnetron sputtering process using 5N pure zinc oxide target doped with 2 wt% of Al2O3 by varying the sputter parameters such as target power, electrode distance and substrate temperature. The measured thickness of the deposited AZO thin films using stylus profiler is in the range of 190 to 1100 nm. The microstructure of the AZO films has been investigated by X-ray diffraction and Scanning Electron Microscope. The AZO thin films have been optimized to a lowest electrical resistivity of 3.7 X 10- 4 Ω cm measured by four-point probe method, and to an average optical transmittance of 84.1% measured in the wavelength range 300-1100 nm using UV-VIS-NIR spectrophotometer. An attempt has been made through this study to fabricate thin film transistors by incorporating the optimized AZO films and the results are discussed in this paper.