An electrochemical study on the nature of trap states in nanocrystalline rutile thin films
An electrochemical study on the nature of trap states in nanocrystalline rutile thin films
复制标题
DOI：
10.1021/jp071438p
复制
发表时间：
2007-07-12
影响因子：
3.7
通讯作者：
Gomez, Roberto
中科院分区：
文献类型：
--
作者：
Berger, Thomas;Lana-Villarreal, Teresa;Gomez, Roberto
对于单晶TiO 2电极，在足够负的电势下观察到电容电流，以诱导填充导带态。除了这些电流之外，纳米颗粒电极在更正的电势处表现出另外一对电容峰，这可以归因于带隙中的电荷陷阱。我们利用三种不同类型的金红石电极的明确的形态和晶体结构来研究这些带隙状态的性质。特别地，已经使用了由取向线组成的纳米结构膜、随机分布的纳米颗粒的膜和光滑的单晶。的循环伏安响应的分析揭示了强烈的依赖于陷阱态浓度上的膜的形态结构。在电极表面改性的结果的基础上，我们提出了一个模型，这些带隙状态的位置在晶界。此外，我们报告了一个新的程序，以制备层次组织的纳米结构，在低温下在水溶液中的纳米颗粒膜上的纳米线直接沉积。从实践的角度来看，该过程允许系统地调整原始样品的内表面积和孔隙率。
For monocrystalline TiO2 electrodes, capacitive currents are observed at potentials that are negative enough to induce the filling of conduction band states. Nanoparticulate electrodes exhibit, apart from these currents, an additional pair of capacitive peaks at more positive potentials, which can be attributed to charge traps in the band gap. We have taken advantage of the well-defined morphology and crystal structure of three different types of rutile electrodes to investigate the nature of these band gap states. In particular, nanostructured films composed of oriented wires, films of randomly distributed nanoparticles, and smooth single crystals have been used. The analysis of the cyclic voltammetry response reveals a strong dependence of the trap state concentration on the morphological structure of the films. On the basis of results concerning the surface modification of the electrodes, we propose a model with a location of these band gap states at grain boundaries. We report, furthermore, on a new procedure to prepare hierarchically organized nanostructures by direct deposition of nanowires onto nanoparticulate films in aqueous solutions at low temperature. From a practical point of view, this procedure allows for a systematic tuning of the inner surface area and the porosity of the original samples.