Transistor Characteristics of Zinc Oxide Active Layers at Various Zinc Acetate Dihydrate Solution Concentrations of Zinc Oxide Thin-film

This paper presents a technique involving a sol-gel deposition method applied to the deposition of zinc oxide thin film for a transistor as a semiconductor layer. This method was used for manufacturing the essential thin films of II-VI semiconductors. Zinc oxide (ZnO) bottom-gate (BG) thin-film transistors (TFTs) have been successfully fabricated at low temperatures. We investigated the electrical characteristics of ZnO thin-film transistors at various concentrations of ZnO solution: 0.02 M, 0.03 M, 0.04 M, and 0.05 M. All of the ZnO films exhibited a hexagonal wurtzite polycrystalline structure with (002) preferred orientation. Atomic force microscopy (AFM) revealed the formation of grains or clusters as a result of the accumulation of nanoparticles, and the grain size increased with increasing solution concentration. The coated ZnO films were employed as the active channel layer in thin-film transistors, and the impact of the solution concentration on the device performance was examined. As the solution concentration was increased, the field-effect mobility increased from 1 × 10–4 cm2/V-s to 1.2 × 10–1 cm2/V-s, the threshold voltage increased from 4.8 V to 11.1 V, and the Ion/Ioff ratio increased from 104 to 106. The on-off ratio (Ion/off) was found to be 106. The 0.05 M ZnO solution performed optimally.