Microwave irradiation effects on electrical and optical properties of ZnO thin films deposited by atomic layer deposition

Abstract

Microwave irradiation effects on ZnO thin films deposited by thermal atomic layer deposition were investigated. Diethylzinc precursor and DI water reactant were used as the Zn and O sources, respectively. After deposition, the microwave irradiation processes with the recipe changing microwave irradiation time at 1, 3, 5, and 10 min were carried out. We observed that the microwave irradiation time affected the electrical, structural, and optical properties of the ZnO films. The crystallinity increased as the irradiation time increased until 5 min, but it decreased at 10 min. When the irradiation time increased, the ratio of oxygen vacancies increased. In addition, excessive oxygen vacancies at 10 min caused Zn-rich, which results in decreasing crystallinity. As one oxygen vacancy generates two electrons, carrier concentration increased with increasing the irradiation time. In contrast, resistivity and Hall mobility decreased as the irradiation time increased. As a result of UV-vis, optical bandgap and average optical transmittance showed a similar tendency to crystallinity. It could be explained by the modified Burstein-Moss effect, which caused by self-energies with excessive electrons. All the average optical transmittance was over 85%, which was suitable for applications as transparent electrodes.