Influence of polarity and hydroxyl termination on the band bending at ZnO surfaces
Influence of polarity and hydroxyl termination on the band bending at ZnO surfaces
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DOI：
10.1103/physrevb.88.235315
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发表时间：
2013-12-30
影响因子：
3.7
通讯作者：
Allen, M. W.
中科院分区：
文献类型：
--
作者：
Heinhold, R.;Williams, G. T.;Allen, M. W.
利用表面灵敏同步辐射X射线光电子能谱（XPS）和实时原位XPS研究了ZnO单晶极性表面羟基封端和向下能带弯曲的热稳定性。在O-极性面上，费米能级的位置可以在大约0.8 eV的能量距离（类似于带隙的1/4）上在导带和带隙之间可逆地循环，这通过使用高达750摄氏度的简单真空（UHV）热处理、加入H2O/H-2和大气暴露来控制表面H覆盖。在约0.9单层的H覆盖率下观察到O-极性面的电子性质中的金属到类超导体的转变。对于H覆盖率小于此，半导体（耗尽）O-极性表面的创建是合理的稳定在超高真空条件下。相比之下，向下带弯曲的锌极性面上的弹性显着更大，和耗尽的表面不能单独通过热处理制备。
Surface sensitive synchrotron x-ray photoelectron spectroscopy (XPS) and real-time in situ XPS were used to study the thermal stability of the hydroxyl termination and downward band bending on the polar surfaces of ZnO single crystals. On the O-polar face, the position of the Fermi level could be reversibly cycled between the conduction band and the band gap over an energetic distance of approximately 0.8 eV (similar to 1/4 of the band gap) by controlling the surface H coverage using simple ultrahigh vacuum (UHV) heat treatments up to 750 degrees C, dosing with H2O/H-2 and atmospheric exposure. A metallic to semiconductorlike transition in the electronic nature of the O-polar face was observed at an H coverage of approximately 0.9 monolayers. For H coverage less than this, semiconducting (depleted) O-polar surfaces were created that were reasonably stable in UHV conditions. In contrast, the downward band bending on the Zn-polar face was significantly more resilient, and depleted surfaces could not be prepared by heat treatment alone.