Influence of humidity on the photoemission properties and surface morphology of cesium iodide photocathode

We report on the photoemission properties of 500 nm thick CsI films photocathodes. The surface morphology and electron diffraction pattern of 500 nm thick “as-deposited” CsI and further “aged” CsI by exposing it to the humid air were investigated by means of transmission electron microscopy. It is observed that photoemission properties are degraded after long term exposure in humid air however there is no change in the film polycrystalline structure. After a 24 h exposure to humid air, the average grain size of CsI films is increased by a factor of three.