Influence of working pressure on the structural, optical and electrical properties of sputter deposited AZO thin films

Abstract

Highly oriented crystalline aluminum doped zinc oxide (AZO) films were sputter deposited on glass substrates and a systematic investigation on the as deposited and etched films was reported for its further application in silicon thin film solar cell. Influence of the deposition pressure (from 2 to 8mTorr) and post-annealing temperature (at 400°C for 5min) on the structural, optical and electrical properties of the as-deposited and etched samples were analyzed. The optimum condition for its reproducibility and large area deposition is determined and found that the depositions made at 8mTorr at 200W having the distance from source to substrate of 9cm. All the AZO films exhibited a c-axis preferred orientation perpendicular to the substrate and their crystallinity was improved after annealing. From the XRD pattern the grain size, stress and strain of the films were evaluated and there is no drastic variation. Optical transmittance, resistivity, Hall mobility and carrier concentration for the as deposited and etched-annealed films were found to improve from 79 to 82%; 2.97 to 3.14×10−4Ωcm; 25 to 38cm2/Vs; 8.39 to 5.96×1020/cm3 respectively. Based on the triangle diagram between figure of merit and Hall mobility, we obtained a balance of point between the electrical and optical properties to select the deposition condition of film for device application.