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

초록

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.

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