Effects of a Pretreatment on Al-Doped ZnO Thin Films Grown by Atomic Layer Deposition

In this study, we investigated the electrical, structural, and optical properties of Al-doped ZnO (AZO) thin films approximately 50 nm thick grown by atomic layer deposition (ALD) on glass substrates at 200 °C. An H2O pretreatment was conducted for all AZO samples. The electrical properties of the AZO thin film were improved after the pretreatment process. The Al doping concentrations were controlled by inserting an Al2O3 cycle after every "n" ZnO cycles while varying n from 99 to 16. As the doping concentration increases, the resistivity decreases and the optical band gap increases. When the Al2O3 cycle ratio is 5%, the electrical resistivity showed the lowest value of 4.66 x 10(-3) Ω cm. A carrier concentration of 1.10 x 10(20) cm(-3), and the optical transmittance exceeding 90% were obtained in the visible and near-infrared region. The thin film was strongly textured along the (100) direction in the X-ray diffraction patterns.