Bi-alkali antimonide photocathodes for high brightness accelerators

Abstract

Alkali-antimonide photocathodes were grown on Si(100) and studied by means of XPS and UHV-AFM to validate the growth procedure and morphology of this material. The elements were evaporated sequentially at elevated substrate temperatures (first Sb, second K, third Cs). The generated intermediate K-Sb compound itself is a photocathode and the composition of K2.4Sb is close to the favored K3Sb stoichiometry. After cesium deposition, the surface layer is cesium enriched. The determined rms roughness of 25 nm results in a roughness domination of the emittance in the photoinjector already above 3 MV/m.