极化效应对ZnO极性面稳定性的影响研究

As a significant component of the physical properties of semiconductors, surface structures and properties are closely related to many applications and therefore an important research areas for semiconductors. ZnO is a semiconductor with wide potential applications. The couple of wurtzite polar surfaces （0001）and (000-1) are generally seen but their stabilizaiton mechanism yet is unclear and some experimental phenomena are hard to understood following the classical theory, being an hot and important question for ZnO research. In this project, a systematical investigation will be done to probe the stabilizaiton mechanism of ZnO polar surfaces. Special attention will be paid for the role polarization effect and the indirect influence from the bulk impurity and defect with polarizaiton field as a medium. These factors are deficient in classical theory but are thought to be crucial for ZnO. At the end of this project a thorough understanding to the stabilization mechanism of ZnO poalr surfaces will be obtained, give out more reasonable explanation to experimental results, and that it will provide references to other similar semiconcductors. It has high academic value to consummate the theory of semiconductor polar surface.

表面结构与性质是半导体物理性质的重要组成部分，与很多实际应用密切相关，也是半导体物理研究的重要领域。ZnO是一种具有广泛应用前景的半导体材料，纤锌矿结构两个极性面（0001）和（000-1）是最常见的表面，但对其稳定机理至今没有达成共识，实验上也存在一些传统理论不能解释的现象，成为了ZnO研究领域的一个重要与热点问题。本项目将对ZnO极性面的稳定机理进行系统研究，特别关注极化效应对极性面结构的影响，以及内部杂质和缺陷通过极化场对极性面结构的间接影响。传统理论对这些因素考虑不足，但我们认为对ZnO将特别重要。项目的完成将充分揭示ZnO极性面的稳定机理，对实验结果作出更加合理的解释，为其它类似材料提供借鉴。还将对半导体极性面理论的进一步完善具有重要学术价值。

实验发现ZnO极性面的结构表现出复杂性和多样性，有一些结构传统表面理论不能给出很好的解释。本项目计划通过第一性原理计算探索ZnO表面结构与材料内部缺陷（杂质）的关系，从一个新的角度研究ZnO极性面的稳定机理。研究发现，由于ZnO很强的离子性，其表面电子结构和III族氮化物等其它半导体有很大区别。ZnO表面没有在体相带隙中形成孤立的表面态，表面态和价带及导带存在明显交叠，这种现象在（0001）面更为突出。这种交叠导致表面和内部很容易发生电荷转移，正是这个原因把表面和内部缺陷密切联系了起来，内部缺陷的变化会影响到表面的形貌。我们认为这就是ZnO极性面结构多样性和复杂性最根本的物理机理。这一结论对于理解ZnO表面相关的其它现象也提供了新的视角。