Influence Of Heat Treatment On Characterization Of ITO Thin Films Prepared By A Sol-gel Spin Coating Process

Indium tin oxide (Sn-doped In2O3, ITO) thin film is an n-type transparent conductive semiconductor material, the band gap is between3.5eV and4.3eV. Because of excellent optical and electrical properties, it is widely used in a variety of optoelectronic devices, such as transparent electrode of solar cells, flat panel displays and gas-sensing devices, and so on. ITO thin films can be formed with a lot of methods, the ITO films grow process of sol-gel method is simple, does not require expensive primeval material and complicated equipment, so it is widely use and research.In this paper, ITO films were prepared by a sol-gel spin coating process from inorganic metal salts as raw materials(InCl3and SnCl4·5H2O). The structure, morphology, conductivity and transmittance of ITO thin films are studied by XRD, FE-SEM, four-point probe and UV-VIS spectrometer. This study is mainly the following two parts:1. ITO films annealed at same annealing time intervals and different annealing temperatures in air by a sol-gel spin coating process. The XRD pattern indicates that the films are polycrystalline with a cubic bixbyite structure and there are no phases corresponding to tin or other tin compounds, meaning that tin atoms are substitutionally doped into In2O3lattices. XRD results also illustrate the annealing temperature improve the degree of crystallinity of the ITO film. SEM images show that the surface morphology has been improved with annealing temperature increased, and the grain size decreases and then increases. The visible light transmittance of ITO films increases and then decreases with the annealing temperature increased. The resistivity decreases sharply and then increases slightly as the annealing temperature increases. These results illustrate the change of annealing temperature is possible to improve the performance of the ITO film.2. ITO films annealed at same annealing temperatures and different annealing time intervals in air by a sol-gel spin coating process. XRD spectra illustrate the structure of the ITO film is still a cubic bixbyite structure, and tin atoms are substitutionally doped into In2O3lattices too. XRD spectra indicates the orientation of crystals is turn from the (222) plane to the (400) plane with the annealing time intervals increase. The SEM images show that with the annealing time increase, the ITO film surface morphology changes, the grain size is larger. The visible light transmittance of ITO film is gradually increase as the annealing time intervals extension. But annealing time interval extension did not make a change rule in resistivity of the ITO film.