Electronic and optical properties of TiO_2 and its polymorphs by Z-scan method

查看全文 作　　者：S. [1]Divya;V P N [1]Nampoori;P [1]Radhakrishnan;A [1]Mujeeb 机构地区：[1]International School of Photonics, Cochin University of Science and Technology 出　　处：《Chinese Physics B》索引2014年第23卷第8期,共5页 基　　金：Project supported by the Funds from the Department of Science and Technology(DST),India 摘　　要：TiO2is a material which has attracted considerable attention from the scientific community for its innumerable properties. TiO2 is known to exist in nature in three different crystalline structures: rutile, anatase, and brookite. Anatase and rutile TiO2 films have been widely characterized for their potential applications in solar cells, self-cleaning coatings,and photocatalysis. In the present report, the third-order nonlinear susceptibilities of TiO2 and its polymorphs, anatase,and rutile, prepared by the sol–gel technique followed by heat treatment are investigated using the Z-scan technique at a wavelength of 532 nm with a duration of 7 ns. Imaginary and real values of χ(3)for amorphous, anatase, and rutile are also calculated and found to be 5 ×10-19m2/V2, 27 ×10-19m2/V2, 19 ×10-19m2/V2, respectively. It is found that the values of the optical constants of amorphous TiO2 after heat treatment vary considerably. It is assumed that this could be due to the variation in the electronic structure of TiO2 synchronous with the formation of its polymorphs, anatase, and rutile.Amorphous TiO2 is marked by the localization of the tail states near the band gap, whereas its crystalline counterparts are characterized by completely delocalized tail states. 关 键 词：二氧化钛 多晶型物 电子结构 光学性质 Z扫描 三阶非线性极化率 金红石型 锐钛矿型