Investigation on the Valance Band Structure of HOPG Using Ultraviolet Photoelectron Spectroscopy System

This paper provides a basic introduction to the principles of ultraviolet photoelectron spectroscopy (UPS), ultraviolet photoelectron yield spectroscopy (PYS), and constant final state yield spectroscopy (CFS-YS) measurements. Different measurements were performed on HOPG, obtaining a series of electronic energy level parameters such as work function <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\Phi=4.56\text{eV}$</tex>, valance band energy <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$E_{V B M}=0.87$</tex> eV, and ionization energy <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$I_{th}=5.35\text{eV}$</tex>. It offers an initial understanding of the surface electronic structure via the ultraviolet photoelectron spectroscopy. The electronic structure of the material surface can be more finely characterized through the comparison and joint analysis of different measurement methods.