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.

Pure MgO powders were synthesized using wet chemical and thermal processes. Purity and crystallinity were used as indicators determining the synthesis. From this, we obtained highly pure and crystalline MgO powders. Using these powders, we could achieve 15~20V lower firing voltage and 10 ~ 15% higher efficiency, depending on the extent of the partly covered area and on sealing temperature. The improvement was proved to be due to surface states that were absent in an MgO film.