论文标题
CSK的稳定性和电子特性$ _2 $ SB表面面
Stability and electronic properties of CsK$_2$Sb surface facets
论文作者
论文摘要
第一原理方法最近在光电研究领域中建立了自己，以提供电子源相关材料的显微镜，量子力学表征。虽然大多数现有研究都集中在块状晶体上，但表面特性的知识对于评估样品的光发作性能至关重要。在密度功能理论的框架中，我们研究了CSK $ _2 $ SB的表面板的稳定性和电子性能，这是一种新兴的粒子加速器的新兴半导体光电模式。考虑到具有Miller指数0和1的表面，并考虑了所有可能的终止，我们发现，在与真空的界面上，原子层可能会大大重新排列，以最大程度地减少相邻碱物种之间的静电排斥。从对化学电位的表面能量的分析中，我们发现沿（111）方向面向表面的偏好。然而，在大的和中间的CS和K中，（100）和（110）平板在能量上是最有利的。所考虑的表面表现出半导体或金属特征。前一种是最稳定的平板（111）平板，其带隙约为1.3 eV，与CSK $ _2 $ SB样品的实验值非常吻合。与CSK $ _2 $ SB光座的发射阈值一致，金属表面的工作功能较低，其功能为2.5 eV。在所有这些结果中，所有这些结果尤其有助于对CSK $ _2 $ sb的微观特性，尤其是多烷烃抗肌的微观特性，并代表了对这种新兴光电座材料类别的持续实验努力的有用补充。
First-principles methods have recently established themselves in the field of photocathode research to provide microscopic, quantum-mechanical characterization of relevant materials for electron sources. While most of the existing studies are focused on bulk crystals, the knowledge of surface properties is essential to assess the photoemission performance of the samples. In the framework of density-functional theory, we investigate stability and electronic properties of surface slabs of CsK$_2$Sb, an emerging semiconducting photocathode material for particle accelerators. Considering surfaces with Miller indices 0 and 1, and accounting for all possible terminations, we find that, at the interface with vacuum, the atomic layers may rearrange considerably to minimize the electrostatic repulsion between neighboring alkali species. From the analysis of the surface energy as a function of the chemical potential, we find a striking preference for surfaces oriented along the (111) direction. Yet, at large and intermediate concentrations of Cs and K, respectively, (100) and (110) slabs are energetically most favorable. The considered surfaces exhibit either semiconducting or metallic character. Of the former kind is the most stable (111) slab which has a band gap of about 1.3 eV, in excellent agreement with experimental values for CsK$_2$Sb samples. Metallic surfaces have lower work function, on the order of 2.5 eV, in line with the emission threshold measured for CsK$_2$Sb photocathodes. All in all these results contribute to the fundamental understanding of the microscopic properties of CsK$_2$Sb in particular and of multi-alkali antimonides in general, and represent an useful complement to the ongoing experimental efforts in the characterization of this emerging class of photocathode materials.
