A study of an electron affinity of cesium telluride thin film

The photoemission spectroscopy using synchrotron radiation has been carried out to study the electron affinity of cesium telluride thin films. We observed a formation of NEA surface on p-type gallium arsenide deposited with cesium telluride. An ultra thin film of cesium telluride is discussed as a possible candidate forming an NEA surface. The electron affinity of cesium telluride thin film was found to increase with time after fabrication. An increase of the affinity resulted in deterioration of a quantum efficiency under laser light exposure with constant wavelength. The surface of photocathode in RF gun can suffer enormous damage easily at the conditioning process of RF gun before electron extraction. A method to refresh the photocathode surface after RF conditioning has been required. A photodetachment process is a candidate to refresh aged/damaged photocathode with X-ray exposure. A recovery of quantum efficiency for the aged photocathode film by this refreshing process is shown.