ZnO as transparent conducting oxide by Atomic Layer Deposition

Zinc Oxide (ZnO) films were deposited on SiO₂/Si and glass substrates by Atomic Layer Deposition using Diethylzinc (DEZ) as the metal precursor and Water (H₂O) as the oxidant over a temperature range of 75°C to 225°C. Here we demonstrated self limiting behavior of the Atomic Layer Deposition and the linear growth of the deposited films by in-situ quartz crystal microbalance (QCM) study. The maximum growth rate was found to be ~1.8 to 2 Å per ALD cycle. The as deposited crystalline ZnO films were found to be c-axis preferentially oriented with dense microstructures, homogeneous grain sizes and low surface roughness. We developed ZnO as ~ 80% transparent conductor with carrier density ca. 10²¹ cm^-3 and a controllable resistivity from the intrinsic level (highly insulating) to 10^-3 Ω-cm without any intentional doping.