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Temperature and wavelength dependence of Fermi-tail photoemission and two-photon photoemission from multialkali semiconductors

Two-photon photoemission is a useful technique for examining interface, surface, and image-potential states in various materials. We report the temperature and wavelength dependences of the two-photon photoemission yield for several multialkali semiconductors used as photocathode materials in commercially available photomultiplier tubes. We also report the dependence on temperature and wavelength of one-photon photoemission associated with the Fermi tail of the electron-occupancy probability distribution, which can mask two-photon photoemission. The results are expected to be of use in entangled-photon photoemission experiments, for which a large value of the two-photon photoemission yield is required.