六角层状氮化硼光电属性的应力调制

项目名称： 六角层状氮化硼光电属性的应力调制

项目编号： No.10874143

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 无线电电子学、电信技术

项目作者： 孙立忠

作者单位： 湘潭大学

项目金额： 29万元

中文摘要： 采用基于密度泛函理论的第一原理方法，我们系统研究了外应力及堆垛缺陷对深紫外光电子材料六角层状结构氮化硼（h-BN）的电子结构及光学性质的调制效应。研究表明，随着流体静压力的增大， AA堆垛从间接带隙转换为直接带隙。六角氮化硼五种堆垛的带边吸收限除AB以外随着流体静压力的增大都发生红移。单轴应力可以对AA堆垛的带隙类型进行调制，并使得AB堆垛的带边吸收限先发生红移，再发生蓝移，而其他堆垛都发生红移。单轴应力对基于双层六角氮化硼片的隧穿磁阻结的隧穿磁阻效应的具有较强的调制效应，随着单轴应变的增大，体系的TMR值近线性增加，并且当单轴应变达到2.51%时，体系的TMR值达到95%，接近于理想的自旋过滤器。我们系统分析了h-BN五种堆垛出现不同单层堆垛缺陷后对h-BN体系的电子结构以及光学性质的影响。我们发现类AE堆垛缺陷在其带隙类型转化中扮演重要角色：h-BN出现类AE堆垛次序的单层缺陷层时，电子跃迁声子辅助能量迅速减小，其体系由间接带隙转化为准直接带隙或直接带隙。同时我们发现这种能带类型转换对堆垛缺陷浓度并不敏感。以上研究为解释实验和理论在h-BN体系能带类型上的分歧找到了理论解释。

中文关键词： 六角层状氮化硼；电子结构；光学属性；应力调控

英文摘要： Using the first-principles method, we systematically study the electronic and optical properties of deep ultraviolet material h-BN under the modulation of external stress and stacking fault. The results show that the band structure of AA stacking changes from indirect to direct at the hydrostatic pressure of 9.19 GPa. As the increase in hydrostatic pressures, the adsorption threshold of h-BN except for AB is red shifted. The uniaxial stress also induces the change of the band structure os AA from indirect to direct one. Moreover， when the uniaxial stress increases, the band-edge absorption threshold of AB stacking is red shifted initially, and blue shifted from 10.53 GPa. For the other stackings, their band-edge absorption thresholds are red shifted as the increase in the uniaxial stress. We also find that the tunneling magnetoresistance effect of the bilayer h-BN based magnetotunnel junction under the uniaxial strain can be effectively modulated. The results show that the TMR of the corresponding system linearly increases as the increase in the uniaxial strain. In particular, TMR of the system can reach to 95% as the uniaxial strain increases to 2.51%, which approach that of a perfect spin filter. We also systematically study the influence of stacking fault on the electric and optical property of h-BN. We find that the AE-liked stacking sequence plays an important role in the band type conversion. When the AE-liked stacking fault introduced into h-BN the kinetic energy is significantly reduced. The materials tend to be quasi-direct band gap semiconductors. And we find that the influence of the AE-liked stacking fault on the electronic structures is insensitive to its concentration. We predict that the AE-liked stacking fault may be the primary reason for the inconsistency between theoretical and experimental results, they have dealt with unique stacking sequence system and the system with stacking fault separately.

英文关键词： h-BN;electronic structure;optical properties;stress modulation