Substrate dependence of CsK2Sb photo-cathode performance

A photo-cathode which is able to generate a highperformance electron beam with large operability is one of the most important devices in the advanced accelerator. In particular, the CsK2Sb photo-cathode is paid attention because it has high robustness and can be driven by visible light. In this study, we performed cathode evaporation on Si(100), Si(111), and GaAs(100) substrates to evaluate the performance dependence on the substrate material and surface state. For each substrate, the cathode performances on the as-received and cleaned substrates were compared. We found that the cathode performance on the cleaned substrate was superior to that on the as-received substrate for all materials. The cathode performances on the cleaned GaAs(100) and Si(100) substrates were similar, but it on the cleaned Si(111) was significantly much lower. This result gave an experimental evidence about substrate surface direction dependence of CsK2Sb photo-cathode performance.