Comparison of Work Functions of Several Materials Measured by XPS and UPS

KeyWord:work function  ultraviolet photoelectron spectroscopy  X ray photoelectron spectroscopy

Abstract:

      In order to compare the differences between the work function values of materials measured by X ray photoelectron spectroscopy£¨XPS£© and ultraviolet photoelectron spectroscopy£¨UPS£©£¬both techniques were used to respectively measure the Au,Ag film samples and monocrystalline silicon cleaned with argon ions,and the Au,Ag,MoO3 film samples,monocrystalline silicon and ITO without any surface cleaning.The calculation methods of work functions for materials measured by XPS and UPS were provided in this paper,and the influencing factors for the uncertainty of the work function values measured by photoelectron spectroscopy were discussed.Results showed that,in the measurement of the metal samples imposed a surface cleaning,the measurement values obtained by UPS and XPS displayed an obvious coherence with high accuracy,while the surface cleaned Au and Ag samples would be covered by an adsorption layer as soon as they were exposed to the air,and their work functions would change quickly.Therefore,when the intrinsic work functions of metal and semiconductors were measured,the sample surface should avoid being exposed to the atmosphere,and it is recommended that the sample surface should be cleaned with argon ion gun if it has been exposed to the atmosphere.This study showed that it is of a certain guiding significance for researchers to adopt reasonable measuring means according to actual test requirements