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Abstract

This chapter discusses the multialkali effects and polycrystalline properties of multialkali antimonide photocathodes. The concept of multialkali effects is aligned with the fact that photocathodes of high sensitivity may be obtained if antimony is combined with more than one alkali metal. Because of the background of its real applications, the characteristics of the multialkali photocathode, especially its integral sensitivity and spectral response in the red and near-infrared light regions, have been improved successively in the recent past. It is believed that this photocathode still has large potential. One of the significant problems in this regard is the influence of the polycrystalline grain sizes and grain boundaries on photoemission. Usually a semiconductor model was used for the multialkali photocathode, but it is really a monocrystal model. This model cannot be used to discuss its spectral response, quantum yield, or integral sensitivity. In addition to the influence of the composition and surface structure of the photocathode, the grain sizes and grain boundaries also have obvious influence on photoemissive properties. The physical basis for the multialkali effect and the influence of the grain sizes and grain boundaries on photoemission are discussed in this chapter.