Effect of water flow rate on properties of zinc oxide thin films prepared using spatial atomic layer deposition

Abstract

In this study, spatial atomic layer deposition (ALD) system is employed to grow zinc oxide films (ZnO) with diethylzinc and water precursors. The H2O flow rate is varied to investigate its effect on electrical, structural and optical properties of the films. The experimental results show that the low H2O flow rates lead to a lower amount of oxygen vacancies compared to higher flow rates. The x-ray diffraction reveals the stress released and crystalline structure repair at high flow rates. The film deposited at 9 sccm corresponding to the saturation point exhibits the highest electron mobility of 32 cm2V–1s–1 and the lowest resistivity of 0.05 Ω-cm. A deposition mechanism is proposed, where the low H2O flow rate requires multiple ALD cycles to complete oxidation of surface ligands, thereby suppressing the oxygen vacancies formation. High H2O flow rates give rise to better ZnO growth, favoring the oxygen vacancies formation and stress release.