1.引言1971年,Fadley等人发现,如果光电子发射角θ(通常定义为光电子从固体表面射出的方向和固体表面之间的夹角)很小,来自固体表面头几个原子层的信息可大大地增强。这因为光电子在同一种材料中有一定的平均自由 1. Introduction In 1971, Fadley et al. Found that if the photoelectron emission angle θ (usually defined as the angle at which the photoelectrons exit the solid surface from the solid surface) is small, the information from the first few atomic layers of the solid surface can be Greatly enhanced. This is because the photoelectrons have a certain average freedom in the same material