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和吸附物的成键性质，因此它的重要性在表面科学领域早已得到公认。然而，它与原子结构和电子结构的关系尚未完全理解。在本课题中，我们研究了功函数的宏观和微观来源与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PbSnO2薄膜，我们用低温扫描隧道显微镜研究了PbSnO2薄膜中电子结构与功函数之间的关系。通过对Au（111）表面Pb覆盖层的驻波观测，阐明了表面电位变化与表面电子态能量移动之间的相关性。观察到的驻波图案解释了表面电子态的能量转移，这与同一系统中的功函数变化一致。

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.