Spectroscopic investigation of in-situ prepared multialkali-based photocathodes

Alkali-based electron sources are characterised by high quantum efliciency and low work function, therefore they are the best candidate to met the specification of laser-driven RF gun. Preparation technology of such a photoemitters is in rapid progress, and the development of multialkali materials represent a promising step. We used Auger Electron Spectroscopy (AES) to investigate in situ grown multialkali photoemitters. Thin films (tens of nanometers scale) of Sb, K and Cs were sequentially deposited on different substrates (MO and stainless steel AISI 304). The procedure has been separately proved to result in an high efliciency photocmitter. -41 each preparation stage and in the final configuration the film was monitored as far as the interfacial intermixing (also with respect to the substrate), the chemical bonding and the presence of contaminants are concerned. In particular, AES was used in conjunction with sputter erosion to obtain the in-depth profile of the film. Emphasis was also on the characterisation of the outermost layers, which is known to mainly determine the photoemissive behaviour of the material.