Synthesis And Characteristic Of ZnO@SnO₂ Transparent Conductive Thin Films With Coating Structure

ZnO and SnO₂ are wide bandage semiconducting oxides and have attracted extensive researches due to their wide applications in transparent conducting field. It is well known that the adsorption of oxygen on the surface and crystal grain boundary of ZnO thin film deteriorates the electricity property dramatically. As for SnO₂ thin film, it is difficult to be corroded, which greatly limits its application. However, the transparent conducting thin film of ZnO@SnO₂ with coating structure can merge the advantages of ZnO and SnO₂ thin films together, which will be more propitious to hasten the studies and application of the transparent conducting thin films.Based on sol-gel method, we prepare the ZnO@SnO₂ powder and transparent conducting thin films with coating structure by using gelatinating in two-step, and study the aluminum and stadiums-doped thin film in this thesis. Above all, the theory of gelatinating in two-step and coating mechanism of ZnO@SnO₂ structure are explored in terms of the property of the colloid. Then the ZnO@SnO₂ powder with coating structure is analyzed by X-ray diffraction (XRD) and X-ray photoelectron spectrum (XPS). The results reveal that the chemical bond of the Sn-O-Zn has been produced by the chemically reacting between SnO₂ and ZnO. And the conditions of the optimally coating are that the Zn/Sn mol ratio is 8/12 and annealing temperature is 550℃, respectively. Moreover, with the aid of the orthogonal-design method, technological conditions of ZnO@SnO₂ transparent conducting thin films are optimized after investigation and analysis of the samples by XRD, atomic force microscope (AFM), scanning electron microscopy (SEM), four-probe measurements and Ultraviolet-visible spectra. The optimally conditions for good performance of transparent conducting thin film of ZnO@SnO₂ with coating structure are as following. The mol ratio of Zn/Sn equals to 9/12, the ageing hour rate is 28 hours, the thickness of thin films is 7 layers and the annealing temperature is 500℃. Particularly after mixing two colloidal sols, the ageing hour rate is 12 hours. Furthermore, the effect of Zn/Sn mol ratio, annealing temperature and thickness of thin films on the ZnO@SnO₂ transparent conducting thin films is discussed. It suggests that the ultraviolet-visible light transmittance of ZnO@SnO₂ transparent conducting thin films is more than 83% with 112Ωsheet resistance. At last, Al, Sb-doped ZnO@SnO₂ thin films are respectively prepared and explored. And the average optical transmittance of Al-doped ZnO@SnO₂ thin films reaches 84% with 98Ωsheet resistance when doping content of Al is 2at. %. While with 3at. % Sb doping content, the transmittance is 75% in visible region with 97Ωsheet resistance.