纳米TiO2表面光生电荷解析

表面与界面电荷性质是纳米材料制备及其应用中应该考虑的重要问题. 详细了解纳米材料的尺寸与表面电荷性质之间的关系是纳米科学研究中的重要课题. TiO2作为一种宽带隙的半导体材料, 因其具有显著的光电响应、良好的化学稳定性和绿色环保性, 在太阳能转换、光催化杀菌及污染处理等方面有着广泛的用途1～5].

Surface Photo-generated Charges Study of Nanometer TiO2

The photo-generated charge property of TiO₂nanoparticles annealed at different temperatures was studied by the field induced surface photovoltage spectrum (FISPS) technique. The powder of TiO₂was prepared and annealed at 400, 600 and 800 ℃, respectively. The crystalline of TiO₂transformed from anatase to rutile with the annealing temperature increasesing. And the photo-generated charges property of TiO₂behaves differently after it was annealed at different temperatures. When the powder was annealed at 400 ℃, the particle size is so small that the energy band can not be formed completely, so the bound exciton state was formed when it was illuminated by the proper incident light, and it inverse antisymmetrically under external field for locatization effect. While, the powder was annealed at 600 ℃, the surface phtovoltaic response presents the characteristics of homojunction for different crystalline interfaces. After being annealed at 800 ℃, the energy band was formed completely and the larger particle size(36nm) was got. Consequently, a band for the dissociation of free exciton emerged in the band edge of the surface photovotaic response distinguished from the band-band transition, and the direction of the photovoltaic response resulted from the free excition is consistent with the external field, that is positive under positive field, and it inverse symmetrically under external field.