Reactively evaporated BeO films: Preparation and electrical and optical properties

Abstract

The transmission, conductivity and thermally stimulated exoelectron emission have been measured for reactively evaporated thin BeO films. The composition of the solid system beryllium-oxygen can be varied within wide limits between beryllium oxide and pure beryllium by varying the evaporation rate at a fixed oxygen gas pressure. Increasing the metal content results in a decreasing transmission mainly due to absorption of light by small beryllium precipitates within the BeO film. The increasing conductivity with increasing beryllium content supports this hypothesis. Some results on thermally stimulated exoelectron emission after irradiation of thin BeO films with X-rays and γ-rays are presented. Pure untreated BeO films exhibit only a weak electron emission, but the emission is increased strongly by different heat treatments. These heat treatments indicate that water adsorption on the BeO surface makes an important contribution to the mechanism of thermally stimulated exoelectron emission. The thermally stimulated emission from beryllium oxide may find a useful application as a nearly tissue-equivalent solid state dosimeter for ionizing radiation; some dosimetric aspects of the investigations are discussed.