XPS analysis on multi alkali photocathode

The characteristics of multi-alkali cathode, making process as well as the application in the second generational image intensifier was introduced, the sealing process between cathodes and envelops was explained, and cathode was fed to pre chamber of XPS analysis instrument. The percentage of atoms of each element in the thickness of different layer of multi alkali cathode was obtained by XPS analysis. First wide spectrum scan on the top surface of multi alkali cathode was made, and then the narrow spectrum scan was made on every element, following by argon ion etching. Etching after a certain time, wide spectrum and narrow spectrum scan on the multi alkali cathode were made;an argon ion etching was carried out until to the interface of glass window. Argon ion etching combined with XPS spectra analysis, atomic percentage of Na elements, K elements and Sb elements was obtained within the multi-alkali cathode film thickness. The results show that the multi-alkali cathode structure is a two-layer structure, i.e. Na2KSb base layer and adsorbed Cs atoms layer. In two film layer, Na2KSb layer is thicker, while the Cs atomic layer is thin, only 2.7% for the entire cathode film thickness. In addition, the number percentage of Na atoms, K atom, Sb atoms does not follow 2:1:1 stoichiometric ratio, and in the entire cathode layer thickness range, the percentage of atoms of the three elements does not remain constant, and does not appear in the ideal state of the atomic percentage of the three elements at a position reached 2:1:1. Theory and practice has proved it is possible to obtain high sensitivity only with strict stoichiometric ratio Na2KSb film. Thus by molecular beam epitaxy, multi-alkali cathode with higher composition control accuracy stoichiometric ratio 2:1:1 could be produced, the higher cathode sensitivity will be obtained.