Transparent Conducting ZnO Thin Films Doped with Al and Mo

Transparent conducting oxide (TCO) thin films are a vital part of photovoltaic cells, flat-panel displays, and electrochromic windows. ZnO-based TCOs, due to the relative abundance of Zn, may reduce production costs compared to those of the prevalent TCO In$_{2}$O$_{3}$:Sn (ITO). Undoped ZnO, ZnO:Al (0.5, 1, and 2 wt.{\%} Al$_{2}$O$_{3})$, and ZnO:Mo (2 wt.{\%}) films were deposited by RF magnetron sputtering. Optimal deposition temperature was found to be 200$^{o}$C. Controlled incorporation of H$_{2}$ in the Ar sputtering ambient increased mobility of undoped ZnO significantly to 48 cm$^{2}$V$^{-1}$s$^{-1}$. H$_{2}$ also appears to catalyze ionization of dopants. This enabled lightly doped ZnO:Al to provide comparable conductivity to the standard 2 wt.{\%}-doped ZnO:Al while demonstrating reduced infrared absorption. Mo was found to be an n-type dopant of ZnO, though material properties did not match those of ZnO:Al. Scattering mechanisms were investigated using temperature-dependent Hall measurements and the method of four coefficients. This abstract is subject to government rights.