Abstract
An apparatus has been constructed for uv photoemission spectroscopy (UPS), which can be used for solid surface analysis under ultrahigh vacuum conditions. A light source consists of a discharge resonance lamp and a differential pumping system. When He I light at 21.2 eV was used, the experimental results showed that a differential pressure of about 109 was obtained between a lamp room and a specimen chamber. Examples of UPS spectra have also been provided for the clean Si (111) 7 ×7 surface and 2O and HO2 chemisorbed Si (111) surfaces. These spectra demonstrate the intrinsic surface state, the valence-band structure and the O2 and H2O chemisorption-induced surface electronic structures. The UPS results for H2O chemisorption revealed that H2O molecules nondissociatively adsorb on the Si (111) 7 × 7 surface, in agreement with previous results by electron energyloss spectroscopy.
