Preparation And Electrical Properties Of Transparent Conductive Oxide Semiconductors

TCO thin films have studied on 20 century early, begun by Badwker in 1907 for the first time. The SnO2 and In2O3 thin films were investigated in 1950, the ZnO thin films springed up in 80 decade 20 century. At present transparent conductive oxide thin films include mainly SnO2,In2O3,ZnO and their dopant system.Transparent conductive oxide thin films exhibit outstanding optical and electrical properties, such as low resistivity and high transmittance in the visible range etc, because of high carrier concentration and wide optical band gap.In this paper, the widely used TCOs were reviewed,the properties and growth techniques of the TCO thin films and many applications in the modern technology were introduced, and the advantages of different preparation technologies and problems were also presented. And also try to discuss the conducting mechanism involving carrier concentration, mobility, scattering,energy band structure, grain boundary and defect. Results shows that:1. ITO thin films of In2O3, exhibit a resistivity of the order between 10-3-10-5?.cm and an average transmittance above 85% in the visible range, and a band-gap energy above approximately 3.55-3.75eV. The indium-tin-oxide (ITO) properties are good, but the availability of indium-tin-oxide (ITO), whose main constituent, indium, is a very expensive and scarce material.So investigator all along to seek semiconductors those are promising as alternatives to ITO for thin-film transparent electrode applications.2. Pure SnO2 belongs to representative insulator, SnO2 and their doped oxide belong to transparent conductive oxide. SnO2 transparent conductive oxide thin films exhibit outstanding optical and electrical properties by doped oxide. Rencent SnO2 transparent conductive oxide thin films include (FTO),(ATO),(PTO).3. ZnO film is a novel II-Ⅳdirect oxide semiconductor with wide band gap energy of 3.3 eV and exciton binding energy of 60 meV at room temperature. ZAO thin films doped with suitable dopants of Al have more excellent optical and electrical properties, and are applied widely to various electrical and optical devices. Al-doped ZnO (AZO) semiconductors are promising as alternatives to ITO for thin-film transparent electrode applications. In particular, AZO thin films, with a low resistivity of the order of 10-3-10-5?.cm and an average transmittance above 85% in the visible range, and a band-gap energy above approximately 3.04 eV. Source materials that are inexpensive and non-toxic, are the best candidates. Recently, ZnO thin films have become one of the focuses of research nationally and worldly, and emerged as the best alternative candidate for In2O3 thin films.