Influence of post-deposition annealing on electrical and optical properties of ZnO-based TCOs deposited at room temperature

The post-deposition modification of ZnO-based transparent conductive oxides (TCOs) can be the key to produce thin films with optoelectronic properties similar to indium tin oxide (ITO), but at a much lower cost. Here, we present electro-optical results achieved for post-deposition annealing of Al-Zn-O (AZO), AZO:H, Ga-Zn-O:H (GZO:H), and Zn-O:H (ZNO:H) thin films deposited by RF sputtering at room temperature. These studies comprise results of thermal annealing at atmospheric pressure, vacuum, forming gas, H-2 and Ar atmospheres, and H-2 and Ar plasmas, which lead to significant enhancement of their electro-optical properties, which are correlated to morphological and structural improvements. The post-deposition annealing leads to an enhancement in resistivity above 40% for AZO, AZO:H, and GZO:H, reaching rho approximate to 2.6-3.5 x 10(-4) Omega cm, while ZnO:H showed a lower improvement of 13%. The averaged optical transmittance in the visible region is about 89% for the investigated TCOs. Such results match the properties of state-of-art ITO (rho approximate to 10(-4) Omega cm and transmittance in VIS range of 90%) employing much more earth-abundant materials. (C) 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim