Prades J D, Hernandez-Ramirez F, Jimenez-Diaz R, Manzanares M, Andreu T, Cirera A, Romano-Rodriguez A, Morante J R
EME/XaRMAE/IN2UB, Departament d'Electrònica, Universitat de Barcelona, C/ Martíi Franquès 1, E-08028 Barcelona, Spain.
Nanotechnology. 2008 Nov 19;19(46):465501. doi: 10.1088/0957-4484/19/46/465501. Epub 2008 Oct 22.
The responses of individual ZnO nanowires to UV light demonstrate that the persistent photoconductivity (PPC) state is directly related to the electron-hole separation near the surface. Our results demonstrate that the electrical transport in these nanomaterials is influenced by the surface in two different ways. On the one hand, the effective mobility and the density of free carriers are determined by recombination mechanisms assisted by the oxidizing molecules in air. This phenomenon can also be blocked by surface passivation. On the other hand, the surface built-in potential separates the photogenerated electron-hole pairs and accumulates holes at the surface. After illumination, the charge separation makes the electron-hole recombination difficult and originates PPC. This effect is quickly reverted after increasing either the probing current (self-heating by Joule dissipation) or the oxygen content in air (favouring the surface recombination mechanisms). The model for PPC in individual nanowires presented here illustrates the intrinsic potential of metal oxide nanowires to develop optoelectronic devices or optochemical sensors with better and new performances.
单个氧化锌纳米线对紫外光的响应表明，持久光电导（PPC）状态与表面附近的电子-空穴分离直接相关。我们的结果表明，这些纳米材料中的电输运受到表面的两种不同方式的影响。一方面，有效迁移率和自由载流子密度由空气中氧化分子辅助的复合机制决定。这种现象也可以通过表面钝化来阻止。另一方面，表面内建电势分离光生电子-空穴对并在表面积累空穴。光照后，电荷分离使电子-空穴复合变得困难并产生PPC。在增加探测电流（通过焦耳热自热）或空气中的氧含量（有利于表面复合机制）后，这种效应会迅速恢复。这里提出的单个纳米线中PPC的模型说明了金属氧化物纳米线开发具有更好和新性能的光电器件或光化学传感器的内在潜力。
