In situ surface study of the activating layer on GaAs (Cs, O) photocathodes

An in situ study of the activating layer on GaAs (Cs, O) photocathodes has been made using Auger electron spectroscopy, relative work function, photo-emission and spatial resolution measuring techniques. The layer thickness, composition and work function reduction have been measured for both single- and two-temperature activations. In order to account for the electron transmission probability and the transverse energy of the emitted photo-electrons it is necessary to consider both the work function lowering and the scattering properties of the activating layer. Further it has been shown that neither the heterojunction or dipole models provide an adequate explanation of the properties of the layer which are more consistent with the cluster model of Burt and Heine (1978).