28.4: Characterization of Negative Electron Affinity for MgO Film by Ultraviolet Photoelectron Spectroscopy

Many attempts to investigate electronic band structures of various metal oxides such as magnesium oxide (MgO) and calcium oxide (CaO) have been made for a long time, but exact electronic band structures of metal oxides have not been achieved successfully so far due to surface charging during measurement analysis except for ultrathin film. In this study, ultraviolet photoelectron spectroscopy (UPS) is introduced and electronic band structure for MgO film has been obtained by using a unique way of heating the film, which suppresses the surface charging of MgO film through improvement of electrical conductivity during measurement. Negative electron affinity has been characterized for MgO film in the measured UPS spectrum. The characteristics of negative electron affinity can be understood as originating from image‐potential states on MgO surface.