Study On Manufacture Process And Characteristics Of Metal & TiO₂ Thin Film Schottky Contact

Ultraviolet (UV) detectors have attracted great interest by researchers, because of its importance both in military and civil. Especially in recent years, with the development of the material technology, UV detector achieves a rapid development. Nowadays, semi-conductor materials using to make UV detectors such as GaN, SiC, ZnO, and diamond are very difficult to manufacture. And at the same time, it has very strict requirements on the manufacture process and experiment conditions, which makes the manufactures process of semiconductor devices based on these materials complicate. But UV detectors based on TiO₂ thin film have advantages over other kinds of UV detectors, It is a mature technique which means that it has lower cost, better stability and simple manufacture process.From the introduction above, our research will concentrate on the manufacture of UV detectors based on TiO₂ thin film. Compared with p-n diodes, Schottky diode has more simple manufacture process and better responsivity. So the major part of our experiment is to make UV detectors based on TiO₂ through adopt Schottky contacting between metal and semi-conduct.In chapter one of this thesis, we will briefly review the literature of UV detectors. By introducing the structure and chemical structure of UV detectors based on TiO₂ thin film, we can obtain deeper comprehension on this kind of UV detector.In chapter two of this thesis, first we introduce the preparation of TiO₂ thin film material. Then we will offer a general picture of the method we choose, the sol-gel method. After preparing nano-TiO₂ thin film, we used X-ray diffraction, atomic force microscope, X-ray photoelectron to describe TiO₂ thin film. The experiment results show that when the temperature is 650℃, the TiO₂ thin film is a crystal form, and the anatase's absorption peak at 25.3°is obvious, which means that we can get good rutile crystal in our experiment condition. Through the process of XPS, we can get lattice oxygen and absorption oxygen on the surface of the TiO₂ thin film, indicating that a large number of oxygen vacancies there. At the same time, compared with the body material's absorption edge (380nm), the absorption edge of our material has blue-shift phenomenonIn chapter three, we will discuss the Schottky Contacting between metal and TiO₂ thin film. After introducing fundamental theory of metal-semiconductor contacting, this thesis will show how to manufacture the metal thin film on the surface of the TiO₂ thin film with radio frequency magnetism sputter. From the four I-V curves of corresponding metal we can draw the following conclusions:1. Al/ TiO₂/Al: The testing current and voltage has perfect linear dependency which indicates that it has ohmic contact between Al and TiO₂ and there is no any rectification.2. Au/ TiO₂/Al: The barrier voltage of Au- TiO₂ Schottky diode is 0.2⁰.3V. When the voltage rises up to 2V, the rectification ratio,barrier height and ideality factor of Au/ TiO₂ Schottky diodes are 125, 1.05eV, 2.68. It has obvious and can be used to make Schottky diodes.3. Cr/ TiO₂/Al: The barrier voltage of Cr- TiO₂ Schottky diode is 0.2⁰.3V. When the voltage rises up to 0.6V, the rectification ratio, barrier height and ideality factor of Cr/ TiO₂ Schottky diodes are 169, 0.88eV, 2.77. It has obvious and can be used to make Schottky diodes.4. Ni/ TiO₂/Al: The barrier voltage of Ni- TiO₂ Schottky diode is 0.3⁰.4V. When the voltage rises up to 2V, the rectification ratio, barrier height and ideality factor of Ni/ TiO₂ Schottky diodes are 79, 1.07eV, 2.7. It has obvious and can be used to make Schottky diodesFrom the discussions above, we can conclude that there is ideal Schottky contacts and rectifications between Au, Cr, Ni and TiO₂ thin films. It meets almost all our requirements making it an ideal took for the manufacture of UV detectors.In the last chapter of this thesis, we will probe into the MSM UV detectors based on TiO₂ thin films. The dark current of MSM UV detector is in the scale of nA. The dark current would be 1.9 nA when the bias voltage is 5V. The low level of dark current and larger responsivity make Schottky diodes based on TiO₂ thin films a very powerful tool. Thus the MSM UV detectors have and will continue to cause great attentions by researchers.