The Optical Properties Of ZnO-TiO₂ Thin Films

In recent years,oxide semiconductor materials have been widely used in transparent electrodes,touch screens,etc.,and thus have attracted the attention of scholars.Compared with today’s oxide semiconductors,which are generally intrinsic oxide materials,compound oxide semiconductor materials have many advantages in terms of electron mobility,photoelectron efficiency,and spectral response range.These advantages make oxide semiconductors more suitable for use in flat-panel displays,smartphones,and solar cells.In this thesis,three kinds of oxide semiconductor thin films,Zn O thin film,Ti O₂ thin film and Zn O-Ti O₂ composite thin film,were prepared on glass and Si substrates by sol-gel method.Its main contents are as follows:1.ZnO thin films and TiO₂ thin films were prepared experimentally,and the effect of sol concentration on the properties of thin films was studied.The results show that the Zn O film has a preferred orientation on the（002）plane,and the crystal quality first increases and then decreases with the increase of the concentration.The Zn O film prepared under the condition of sol concentration of 0.48 mol L^-1 has a relatively flat surface,the average particle size is 463.1nm,the light transmittance is about 85%,and the forbidden band width is 3.71 e V.During the preparation process,it was found that the grains of the thin films were gradually refined with the increase of the sol concentration.When the sol concentration is 0.71 mol L^-1,the particle size of the Ti O₂ film surface is neatly arranged and the voids are small,the average particle size is 229.3 nm,and the（101）crystal plane is the preferred orientation.The absorbance of the film is positively correlated with the concentration of the sol.At the optimum concentration,the band gap of the film is 3.48 e V.2.The ZnO-TiO₂ composite film was regulated by annealing,and its effect on the film properties was explored.The research results show that when the annealing temperature is 400and 500℃,there are both hexagonal wurtzite and anatase diffraction peaks of the sample,and Zn O and Ti O₂ do not start to recombine.When the annealing temperature was increased to600℃,cubic Zn Ti O₃ appeared and was still maintained at 800℃.It can be seen that when the annealing temperature is≥600℃,Zn O and Ti O₂ undergo a composite reaction to form Zn Ti O₃,and the particles on the surface of the composite film are densely arranged with an average particle size of 141.6 nm.Due to the formation of Zn Ti O₃ in the sample,the absorbance of the composite film was significantly enhanced,and the band gap was reduced to 3.33 e V.3.Under the same annealing temperature（600℃）conditions,Zn O-Ti O₂ composite films of different composition were prepared,and the effects of different ratios of zinc and titanium on the microstructure and optical properties of the Zn O-Ti O₂ composite films were further explored.The results show that with the increase of Zn²⁺content,the absorbance of Zn O-Ti O₂composite film in ultraviolet region and visible light region is obviously stronger than that of other samples.When Zn:Ti is 0.67:0.33,the minimum forbidden band width is 3.03 e V.This sample still has low roughness,and the average particle size is 133.4 nm.