Film thickness, strain and atomic structure dependencies on the work function

物质的功函数反映了表面的拓扑结构、吸附物质的成键性质，因此它的重要性在表面科学领域早已被认识到。然而，它与原子结构和电子结构的关系还没有完全弄清楚。在本项目中，我们研究了功函数的宏观和微观来源以及固体表面的原子结构、化学成分和应变之间的关系，特别是对于超薄膜的情况。我们用低温扫描隧道显微镜研究了铅超薄膜的电子结构和功函数之间的关系。通过对Au(111)表面铅覆盖层的驻波观测，阐明了表面电势变化与表面电子态能量移动之间的关系。观测到的驻波图案解释了表面电子态的能量移动，这与同一系统中功函数的变化是一致的。

Work function of the matters reflects the topology of the surface, bonding nature of the adsorbates and hence its importance has long been recognized in the field of surface science. However, its relationship to the atomic structure and electronic structure has not been understood fully yet. In the present project, we have investigated the relationship between both the macroscopic and microscopic origin of the work function together with the atomic structure, chemical composition, and strain at solid surfaces, especially for the cases of ultrathin films.We have studied the correlation between the electronic structure in the Pb ultrathin film and work function by low-temperature scanning tunneling microscope. Correlation between the surface potential change and the energy shift in the surface electronic state has been clarified by the standing wave observation for the Pb overlayer on the Au(111) surface. The observed standing wave pattern explained the energy shift in the surface electronic state, which is in agreement with the work function change in the same system.