Preparation and characterization of ZnO transparent semiconductor thin films by sol–gel method

Transparent semiconductor thin films of zinc oxide (ZnO) were deposited onto alkali-free glass substrates by the sol–gel method and spin-coating technique. In this study, authors investigate the influence of the heating rate of the preheating process (4 or 10 °C/min) on the crystallization, surface morphology, and optical properties of sol–gel derived ZnO thin films. The ZnO sol was synthesized by dissolving zinc acetate dehydrate in ethanol, and then adding monoethanolamine. The as-coated films were preheated at 300 °C for 10 min and annealed at 500 °C for 1 h in air ambiance. Experimental results indicate that the heating rate of the preheating process strongly affected the surface morphology and transparency of ZnO thin film. Specifically, a heating rate of 10 °C/min for the preheating process produces a preferred orientation along the (0 0 2) plane and a high transmittance of 92% at a wavelength of 550 nm. Furthermore, this study reports the fabrication of thin-film transistors (TFTs) with a transparent ZnO active channel layer and evaluates their electrical performance.