A Study on the Effect of Base‐Reactant in Low‐Temperature Atomic Layer Deposition of Zinc Oxide

Abstract

During the low‐temperature atomic layer deposition (ALD) process, residual carbon from the unreacted ligand of precursors causes deterioration in the properties of grown materials. Herein, a simple approach using a base solution as a reactant to reduce residual carbon and improve the low‐temperature ALD reaction is proposed. NaOH dissolved in H2O is used as the reactant base solution and diethyl zinc is used as a reactant. The effects of the base‐reactant on the ZnO film growth are analyzed using X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), photoluminescence (PL), and thin‐film transistor (TFT) measurements. The crystallinity, grain size, and Zn and O contents of the ZnO thin films gradually increased as the concentration of NaOH increased (0, 10, 20, and 30 wt%). Residual carbon occupying Zn sites is reduced as NaOH concentrations increased. The unintended heavily doped state induced by the residual carbon during the low‐temperature ALD process is improved, and the ZnO TFT device fabricated with the NaOH/H2O solution also shows improvements in its field‐effect mobility and the on/off current ratio. This simple approach, using the base solution as the reactant during the low‐temperature ALD process, effectively improves the quality of the grown film with low carbon impurities.