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

在研究工作中，测量了掺杂Li_2O形成的透明、c轴取向、高电阻率氧化锌的光导现象。得到了以下结果，特别是氧在表面的解吸和还原主要控制了光导性能。1)在两个光能区（3.2 eV和3.5 eV）观察到光辐照的电流加速。从受控气氛下的测量中，证实了前者的加速是由于能带之间的电子激发引起的，后者是由于表面氧的脱附（还原）引起的。随着3.5 eV光照射的切换，观察到电阻率的增加和减少。而在真空或氮气中未观察到黑暗中电阻率的增加。在高湿气氛下，光还原和再氧化速度加快，复制性能稳定。在3.2 eV光照射下，大气的影响小于3.5 eV光的影响。2)机械磨削抑制了光还原电阻率的降低。通过在空气中以600℃的温度加热样品来恢复这种变化。XPS测量显示，地面样品表面有一层OH涂层，这应该限制了氧的脱附。3)恒定偏压下电流沿c轴方向的光激发大于沿其他方向的光激发，且光激发取决于施加的偏压。在较大的施加偏压下，观察到较大的激励。在另一个方向的偏倚测量中没有观察到这种依赖性。由于氧化锌的c轴为压电极化方向，因此可以判断，由于电场的作用，压电晶格畸变改变了表面氧的结合条件。实验结果表明，通过施加电场可以控制压电氧化锌表面的光还原过程。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