Properties of low indium content Al incorporated IZO (indium zinc oxide) deposited at room temperature

A very low indium content (35 cation % In) a-IZO film, denoted as IZO35/65 or a-ZIO, was fabricated at room temperature. The effect of aluminum (Al) incorporation in IZO35/65 was studied systematically, and reasonably high electrical conductivity and optical transmittance were obtained. After Al doping to an optimum extent, the conductivity was interestingly increased 3 times higher than that of a-ZIO, and this effect could not be attributed to the formation of Al clusters as a further increase in Al led to a significant drop in conductivity. Nonlinear and U-shape resistivity-temperature relationship was observed for some Al doped samples. In addition, an obvious conductivity increase accompanying by the Al2O3 nano-crystallites formation was observed, which provided new evidence to the insulator-metal transition model reported by Nagarajan et al. [Nature Mater. 7, 391 (2008)] recently.