Application And Study On TiO₂ Film Prepared By Self-assembly Method

In recent years, for the urgent needs of scientific research, military and civil, ultraviolet (UV) detection technology has become one of the most popular in the international research field of photo-detectors. With the people's in-depth study, traditional UV detector and materials which are use to made into UV detection also made headway. Which UV photomultiplier tubes and silicon-based UV detectors have been to show their talents in business and the military. But the two devices are not only costly, low efficiency, are not easy to adapt to the use in harsh environment, they still have the problem with short life, so researchers invested a lot to research and development of new solid-based semiconductor UV detection technology.The current research on wide-band-gap semiconductor have developed rapidly, it is the material foundation for the UV detectors based on wide-band-gap semiconductor to replacing of UV photomultiplier tubes. Now many wide-band-gap semiconductors such as GaN, ZnO, SiC and diamond have been used for UV detectors. However, the preparation of these materials is difficult, production process of the devices based on them is also difficult, so that these technologies develop slowly. Therefore, in order to solve these problems, people are trying to find superior performance, low cost, simple process of alternative materials. The TiO₂ is semiconductor materials as a band gap for the 3.0-3.2eV. Its visible light absorption coefficient is small, while it has a strong UV absorption properties following UV 380nm. And its chemical and physical stability is good and heat resistance is excellent. For other wide-band-gap semiconductor, preparation of the nano TiO₂ film is relatively simple. Thus, the TiO₂-based UV detectors will be better than the other solid probe, and can well adapt to the harsh environment.Therefore, for the nano TiO₂ features, this paper presents the nano TiO₂ film is prepared by self-assembly and to use for UV detectors. We are looking for a preparation process with simple equipment, simple operation, mild reaction conditions, low cost and the ability to adapt quantity production. Based on TiO₂'the feature of wide-band-gap, we used various means to validate and probe that TiO₂ film prepared self-assembly have possibility to be use for meatel-semicongductor-metal (MSM) UV detector, and produced a UV detector to analyse its performance in depth.The following is the principle of preparing of TiO₂ film by self-assembly. The feature of TiO₂ film is studied. We use X-ray diffraction to analyse the TiO₂ film prepared by self-assembly, and result shows the diffraction peak of the TiO₂ film is at 25.3°which indicates that the film is anatase. The UV-Vis spectrum shows the absorption edge of TiO₂ films on quartz substrate is about 310nm, while the quartz substrate on the non-absorption of light within this scope, it proves TiO₂ thin films prepared by self-assembly in the ultraviolet range with good absorptive capacity. The morphology of the films is smooth and dense as indicated by the SEM photography. The XPS result shows that the ratio between titanium and oxide is 1to 1.84 in the TiO₂ film prepared by self-assembly. As that prepared by sol-gel, the content of oxide in crystal lattice increases 38.6%, which means film prepared by self-assembly have less oxygen defects and better quality.After the analysis of structure and working principle of MSM ultraviolet detectors, we produced the UV detector based on TiO₂ film prepared by self-assembly. The TiO₂ film grew on quartz substrate. The device's I-V curve indicates that Schottky contact is formed of Au and TiO₂. Under 5 V applied bias, the dark current of the UV detector is 5.95 nA. Under irradiation of 250 nm UV light, the photo current is 21.9μA. The photo response isn't obvious until the wavelength of incident light was shorter than 350nm which are agreed with absorption edge. The peak responsivity of 73.65 A/W is found under irradiation of 260 nm UV light. The rise time of the device is 3.664 s and the decay time is 4.183 s.