Photoinduced oxygen release and persistent photoconductivity in ZnO nanowires.
Photoinduced oxygen release and persistent photoconductivity in ZnO nanowires.
复制标题
光诱导的氧气释放和ZnO纳米线中的持续光电导率。
DOI：
10.1186/1556-276x-6-404
复制
发表时间：
2011-05-31
影响因子：
--
通讯作者：
Ren Z
中科院分区：
文献类型：
--
作者：
Bao J;Shalish I;Su Z;Gurwitz R;Capasso F;Wang X;Ren Z
研究了单个 ZnO 纳米线的光电导性。在紫外线（UV）照射下，观察到感应光电流在空气和真空中都持续存在。它们对空气中紫外线强度的依赖性可以通过光生空穴引起的氧解吸引起的光致表面耗尽深度减小来解释。观察到的光响应在真空中要大得多，并且以慢得多的增加速度超出空气光响应。达到最大值后，只要保持良好的真空度，它通常会无限期地持续下去。一旦真空被破坏并进入空气，光电流就会迅速衰减到典型的空气光响应值。真空中额外的光电导性是通过容易被泵出的吸附表面氧的解吸来解释的，随后晶格氧的解吸进一步减慢，导致电导率增加的富锌表面。 ZnO 表面暴露于空气后，吸附-解吸平衡完全恢复，这表明在紫外线照射下，ZnO 表面正在积极“呼吸”氧气，这一过程在纳米线中因其高表面积与体积比而得到进一步增强。
Photoconductivity is studied in individual ZnO nanowires. Under ultraviolet (UV) illumination, the induced photocurrents are observed to persist both in air and in vacuum. Their dependence on UV intensity in air is explained by means of photoinduced surface depletion depth decrease caused by oxygen desorption induced by photogenerated holes. The observed photoresponse is much greater in vacuum and proceeds beyond the air photoresponse at a much slower rate of increase. After reaching a maximum, it typically persists indefinitely, as long as good vacuum is maintained. Once vacuum is broken and air is let in, the photocurrent quickly decays down to the typical air-photoresponse values. The extra photoconductivity in vacuum is explained by desorption of adsorbed surface oxygen which is readily pumped out, followed by a further slower desorption of lattice oxygen, resulting in a Zn-rich surface of increased conductivity. The adsorption-desorption balance is fully recovered after the ZnO surface is exposed to air, which suggests that under UV illumination, the ZnO surface is actively "breathing" oxygen, a process that is further enhanced in nanowires by their high surface to volume ratio.