表面吸附污染对多晶铜和金功函数的影响

Influence of surface adsorptions and contaminations on work function of polycrystalline Cu and Au

功函数是金属光阴极的一项重要特性,决定了光电子发射量子效率。金属表面在大气环境中容易受表面吸附污染的影响,从而改变表面功函数,并可能影响光电子发射性能。本工作通过光电子能谱的方法,研究常用做光阴极材料的多晶铜和金表面在大气环境中的吸附污染,及其对表面功函数的影响。根据紫外光电子能谱的测量,发现铜和金金属表面存在吸附污染时功函数相比纯净金属表面分别降低约0.1 e V和0.7 e V。利用X射线光电子能谱分析发现有机分子吸附污染使得金样品的表面功函数降低;而对于铜样品表面,导致功函数降低的因素包括有机分子吸附和表面氧化。本研究对光阴极的应用具有指导意义。

Work function is one of the most important properties of metal photocathodes. It will determine the quantum efficiency of photoemission. In the atmosphere environment,there would be adsorptions and contaminations on the metal surface,which may change the work function and even influence photoemission properties. Here,photoelectron spectroscopy methods（ XPS and UPS） were introduced to study the surface adsorptions and contaminations of polycrystalline Cu and Au samples and their influence on the work function. According to measurements of ultraviolet photoelectron spectroscopy（ UPS）,work function decreases of 0. 1 e V and 0. 7 e V were found respectively for Cu and Au with surface contaminations. X-ray photoelectron spectroscopy（ XPS） was used to determine the surface chemical states. For Au surface,adsorptions of organic molecules led to a large decrease of work function. For Cu surface,work function decrease was resulted from both organic adsorptions and surface oxidations. This work could help proper applications of metal photocathodes.