目的 研究分子吸附在不同的 ZnO 表面时,体系的稳定性、电子结构、紫外光吸收情况。 方法根据第一性原理密度泛函理论,首先对 O2 和 H2O 分子分别吸附在完备的 ZnO 和具有氧空位的 ZnO 单层膜表面进行结构优化,然后分析不同体系的电子结构和光学性质。 结果 通过吸附能可知,分子吸附有利于系统稳定性的提高,其中氧分子吸附最为明显;能带和态密度图显示,分子吸附有利于电子在导带和价带之间的跃迁;差分电荷密度图表明,分子吸附的所有体系都存在电子转移,吸附分子和薄膜之间存在相互作用;光吸收图显示,分子吸附的 ZnO 体系光吸收明显增强。 水分子吸附在含氧空位的 ZnO 单层膜上时,体系具有较强的紫外吸收、较高的载流子浓度、较小的载流子有效质量以及较好的稳定性,是比较理想的紫外探测材料。 结论 ZnO 单层膜中氧空位和实验环境中的氧气和水汽均能影响体系的紫外响。研究结果可为 ZnO 基薄膜紫外探测器的发展提供参考。

Objective To study the stability, electronic structure and the UV absorption of ZnO by surface molecular absorption. Methods Based on first-principle calculations within density functional theory, we firstly optimized the structures of different ZnO systems. The systems included O2, H2O molecules adsorbed onto the pure ZnO films and the ZnO films with oxygen vacancies. Then, we calculated the electronic structure and optical properties of different ZnO monolayers. Results By calculation of adsorption energy, we found that molecular adsorption was beneficial for improvement of stability of the systems. And the most obvious was oxygen molecular absorption. From the energy band and density of states figures, we found that molecular adsorption benefited the electron transition between valence band and conduction band, which could improve optical absorption. The figure of charge density difference indicated there was interaction between surface molecules because of charge transition between ZnO and surface molecules. Optical absorption figure displayed the improvement of optical absorption. By comparison, we suggested that water molecular adsorption on ZnO monolayer with oxygen vacancies was the best system because it had the stronger UV absorption, higher carrier concentration, smaller carrier effective mass and better stability. Conclusion The oxygen vacancies in the ZnO monolayer and the oxygen or water vapor in experimental environment influenced the UV response of ZnO. We hope our calculations could provide reference for the study on UV detector of ZnO films.