VUV-induced radiation ageing processes in CsI photocathodes studied by microscopy and spectroscopy techniques

CsI thin film photocathodes of 600 nm thickness deposited on polished Al surfaces by resistive evaporation technique were studied by angle-resolved X-ray photoelectron spectroscopy (ARXPS), before and after UV-irradiation under vacuum. It is shown that the "UV-irradiated" sample keeps the stoichiometric ratio Cs:1 unchanged (1:1) while it shows a higher concentration of carbon in comparison with "as-deposited" samples. The morphology of the "as-deposited" sample is strongly affected after VUV-irradiation. The consequence of such effects on the physical and chemical properties of the "as-deposited" and "UV-irradiated" CsI thin film photocathodes is discussed. (C) 2009 Elsevier B.V. All rights reserved.