Study On Preparation And Properties Of Solution-processed ZnO Thin Film

Microelectronic technology changed our lives with it’s half a century’s development. Development of semiconductor material is the basis of development of microelectronics. From the initial silicon germanium semiconductor material to compound semiconductor material, more and more types of semiconductor material appeard. Transparent oxide semiconductor material has great prospects in the field of liquid crystal display and electronic papers, so it becomes one of the hot researches in domestic and owerseas in the 21 st century. Zinc oxide has been extensively studied as a typical transparent oxide semiconductor material. Field-effect transistor(FET) is the most basic and important device in microelectronics, now silicon is the basic material of FET. In LCD technology, active matrix driver circuit based on thin film transistor(TFT: Thin-Film Transistor) has become a mainstream technology. With the rapid development of zinc oxide thin film material, zinc oxide TFT will replace conventional silicon TFT to achieve a transparent display in the field of liquid crystal display. Zinc oxide thin films as the active layer for transporting carrier play a key role to characteristics of zinc oxide TFT. Preparing excellent quality film is the main way to improve the electrical and optical properties of zinc oxide TFT. In this paper, the sol- gel method and hydrothermal treatment process were used to prepare zinc oxide film. The main work is as follow:(1) Overall refractive index of the film increases from 1.70 to 1.79 at the wavelength of 500 nm, and porosity decreases from 25.14% to 17.60%,when the hydrothermal treatment temperature increases from 110 to 130℃ ℃,analyzed by spectroscopic ellipsometry through the three-layer structure model. Zinc oxide layer was divided into a rough surface layer and a dense inner layer to analyze through four-layer structure model because of lower refractive index and large porosity analyzed through three-layer structure model.(2) The effects of hydrothermal treatment temperature on microstructure optical properties and crystal structure were studied by Spectroscopic ellipsometry and atomic force microscope(AFM). Results indicate that the optical band gap of the film increases from 3.19 e V to 3.31 e V, and the surface roughness of the film decreases from 22 nm to15nm when the hydrothermal treatment temperature increases from 110 to 130℃ ℃. However, when the treatment temperature exceeds 140 ℃, the quality of film is remarkably deteriorated, comparing to the quality of 130℃.(3) Porosity of internal dense layer in zinc oxide thin films was validated about 4% by double B-EMA model.(4) The effects of hydrothermal treatment pressure on microstructure optical properties and crystal structure were studied by Spectroscopic ellipsometry. Results indicate that the surface roughness of the film increases from 21.8nm to 42.6nm when the filling ratio increases from 30% to 52.5% and the optical band gap of the film increases from 3.19 e V to 3.31 e V when the filling ratio increases from 30% to 45.0%.(5) hydrothermal method of 30% filling ratio and 130℃ gets the similar optical properties as thermal annealing of 500℃. All work indicates that hydrothermal method decreases the temperature of treatment when depositing zinc oxide thin films by solution method.