Control of Photo-Reduction of Zinc Oxide with Piezoelectric Property by Electrical Field

在研究工作中，测量了Li_2O掺杂形成的透明、晶体c轴取向、高电阻率的氧化锌的光导现象。主要研究结果如下：1)在3.2 eV和3.5 eV两个光能区，观察到光辐照加速电流。从控制气氛下的测量证实，前者的加速是由于带间的电子激发，而后者是由于表面的氧脱附(还原)。在3.5 eV的光照条件下，样品的电阻率随照射时间的延长而增大或减小，而在真空或氮气中未观察到暗时的增大。在…中，光还原和二次氧化速度加快，复制性能稳定较高湿度的大气。大气对3.2 eV光的影响小于3.5 eV光的影响。2)表面机械研磨抑制了光还原引起的电阻率下降。通过在空气中将样品加热到600ﾟC来恢复这种变化。XPS测试表明，羟基包覆在研磨样品的表面，限制了氧的脱附。3)在恒定偏压下，电流中c轴方向的光激发大于其他方向的光激发，且这种激发依赖于外加的偏压。外加偏压越大，激发越大。在对施加在另一个方向上的偏差的测量中没有观察到这种依赖性。由于氧化锌的c轴是一个压电极化方向，因此判断出压电晶格的变形改变了表面氧的结合状态，从而证实了通过外加电场可以控制压电氧化锌表面的光还原过程。较少

In the research work, the photo conduction phenomena have been measured for zinc oxide with transparency, crystal c-axis orientation and high resistivity formed by doping of Li_2O.The following results have been obtained, especially for the desorption and reduction of oxygen on the surface which controlled the photo conduction properties mainly.1) The current acceleration by photo irradiation was observed at the two photo energy region (3.2 and 3.5 eV). From the measurement under the controlled atmosphere, it was confirmed that the former acceleration was due to the electron excitation between the band and the latter was due to the oxygen desorption (reduction) on the surface. The increase and decrease in the resistivity was observed with the switching of the irradiation of the light of 3.5 eV.While the increase in resistivity in dark was not observed in vacuum or nitrogen. The photo reduction and the re-oxidation rate were accelerated and the duplication property was stabilized in the … More high humid atmosphere. The effect of atmosphere under the irradiation of light of 3.2 eV was smaller than that of 3.5 eV.2) The decrease in the resistivity by photo reduction wa depressed by the grinding the surface mechanically. This change was restored by heating the sample at 600ﾟC in air. The XPS measurement showed the coating by OH on the surface of the ground sample, which should restrict the oxygen desorption.3) The photo excitation in the current under the constant bias along the c-axis was larger than that along the other direction and this excitation depended on the applied bias. The larger excitation was observed under the larger applied bias. Such dependence was not observed in the measurement for the bias applying on the other direction. Since the c-axis of zinc oxide is a piezoelectric polarizing direction, it has been judged that the binding condition of oxygen in the surface changed by piezoelectric lattice distortion with the electrical field.From these results, it was confirmed that we could control the photo reduction process on the surface of piezoelectric zinc oxide by applying electrical field. Less