Effects Of H_2 Ambient Annealing In Fully 002-textured Zno:ga Thin Films Grown On Glass Substrates Using Rf Magnetron Co-sputter Deposition

摘要

Gallium doped zinc oxide (ZnO:Ca) thin films were grown on glass substrates using RF magnetron co-sputtering, followed by H_2 ambient annealing at 623 K to explore a possibility of steady and low-cost process for fabricating transparent electrodes. While it was observed that the ZnO:Ga thin films were densely packed c-axis oriented self-textured structures, in the as-deposited state, the films contained Ga_2O_3 and ZnGa_2O_4 which had adverse effect on the electrical properties. On the other hand, post-annealing in H_2 ambient improved the electrical properties significantly via reduction of Ga_2O_3 and ZnGa_2O_4 to release elemental Ga which subsequently acted as substitutional dopant increasing the carrier concentration by two orders of magnitude. Transmittance of the ZnO:Ga thin films were all over 90% that of glass while the optical band gap varied in accordance with the carrier concentrations due to changes in Fermi level. Experimental observation in this study suggests that transparent conductive oxide (TCO) films based on Ga doped ZnO with good electrical and optical properties can be realized via simple low-cost process.