CsK2Sb GROWTH STUDIES, TOWARDS HIGH QUANTUM EFFICIENCY AND SMOOTH SURFACES∗

The properties of CsK2Sb, make this material an ideal candidate as photocathode for electron injector use. Producing photocathodes with quantum efficiencies of 5 % and greater at 532 nm poses no challenge, nevertheless the traditional growth mechanisms, which are based on a sequential deposition of Antimony, Potassium and Cesium at a range of temperatures up to 150◦C yield a rough surface with a rms roughness in the range of 25 nm, determined by AFM [1]. Surface roughness in this region impacts the emittance. Whereas thermal sequential deposition gives a roughness on the order of the film thickness, for high gradient accelerators, we need a roughness on the order of 1 nm in order to preserve low emittance. Studies are performed to optimize roughness. Various growth procedures are exploited and the resulting samples’ surface roughness compared.