Photocathode study to reduce noise

Energy loss spectroscopy was used in a study of the Ge(100)- Cs-O system. A characteristic loss at 3 eV was identified and is ascribed to a transition between surface bands. The results are interpreted in terms of a model which requires different overlayer structures (depending upon composition) and a work function minimum at 1 monolayer of Cs and 1/2 monolayer of oxygen. More than 15 years after its discovery, Na2KSb(Cs) remains an important photocathode material, but control of its formation remains a problem. In the present studies Auger electron spectroscopy (AES) was used to determine the atomic species present in the surface region during formation of Na2KSb(Cs) films. It was found that the electron bombardment incidental to the use of the AES technique could cause sample changes, but this problem was eliminated for samples that were heated during or after constituent depositions. The Ge(100)/Cs/O photosurface and surfaces at intermediate stages of activation are characterized in terms of photoemission work function, Auger electron spectroscopy (AES), low energy electron diffraction (LEED), and elastic specular electron reflectivity (ESER). An electrical and structural model is proposed for Ge/Cs/O which is consistent with this data. A number of experiments are reported which investigate the sensitivity of the Ge/Cs/O surface to deviations from chemical and structural perfection.