In ultra-violet photoemission spectroscopy measurement it is more precise survey of work function of Au and affinity of GaAs by applying a negative tension on the sample

which is larger than the difference of work functions between the sample and spectrometer. The work function of the spectrometer is also derived. The structure of s-p bands and d bands of polycrystal gold from valence band spectra (VBS) with tension appears the same with zero biased. There is no obvious difference for the s-like states around Ga and the p-like around As of GaAs in comparison of two cases with different biassing for either clean surface or Au deposition on. The continous background of the secondary electrons and inelastically scattered electrons in the VBS is eliminated with negative biassing on.