The influence of temperature on the oxidation of cesiated GaAs

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Abstract
We report on investigations of the oxidation process of cesiated (100) GaAs surfaces by means of photoelectron spectroscopy (UPS; hν=21.2 eV). Discrete steps of the reaction are found as a function of temperature and interpreted in terms of molecular adsorption layers at 90 K, cesium suboxides at 170 K, and As–O bonds at 280 K. Cesium suboxides are discussed as essential surface compounds in negative electron affinity (NEA) photocathodes because of their low work function. According to our results the existence of these compounds would be limited to a very narrow range of oxidation.