Role of growth temperature on the structural, optical and electrical properties of ZnO thin films

Present study focuses on the influence of growth temperature on electrical and optical properties of polycrystalline ZnO thin films on sapphire substrates grown by atomic layer deposition technique. Dimethylzinc and de-ionized water were used as precursors by varying the growth temperature ranging from 70 to 130 °C. X-ray diffraction pattern confirms the formation of hexagonal wurtzite phase of ZnO with preferred (103) orientation. AFM results infer the growth of good quality films with root mean square roughness ∼1 nm for all these films having same thickness. The free carrier concentration and mobility of samples is found to increase whereas resistivity decreases with increasing growth temperature. The electrical results are well corroborated on the basis of photoluminescence and X-ray photoelectron spectroscopy. Photoluminescence and Raman measurements show that these ZnO thin films have very low defect concentrations. In particular, this study demonstrates that a device quality ZnO material with improved electrical parameters is obtained at the level of 100 °C which can be used for applications such as Schottky diodes for cross-bar memory applications and in hybrid organic/semiconductor junction devices. - Highlights: • Influence of growth temperature on various properties of ALD grown ZnO thin films. • Very smooth surface with root mean square roughness ∼1 nm. • Free carrier concentration and mobility increases with growth temperature. • Device quality ZnO films (improved electrical parameters) are obtained at 100 °C