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As the photoelectric conversion material, semiconductor photocathode plays an important role in the development of vacuum photodetectors and electron sources, and the efficiency and stability of electron emission have always been the focus in photocathode applications. Photocathode is based on the external photoelectric effect. Different from the internal photoelectric effect, photoelectrons generated by light excitation inside the cathode must overcome the surface barrier to escape into the vacuum, so the level of the photoemission ability is closely related to the surface properties. The preparation process usually includes surface cleaning and activation, wherein the activation process under the ultrahigh vacuum condition is regarded as an irreversible and evolutionary process over time. How to characterize the cathode surface in situ is particularly important for understanding the mechanism of photoemission generation and degradation. Nowadays, the surface characterization methods including photoelectron spectroscopy, synchrotron x-ray characterization, electron diffraction, scanning probe microscopy, spectral response measurement, and photoreflectance spectroscopy are utilized as assisted evaluation tools to prepare photocathodes. Here, we present a newly developed integrated ultrahigh vacuum facility for photocathode preparation and in-situ characterization. With this system, the surface cleaning, activation and degradation processes for semiconductor photocathodes were effectively characterized by photoelectron spectroscopy and spectral measurement. The integrated photocathode preparation and characterization system can realize in-situ multi-information characterization in ultra-high vacuum environment, and the element composition and chemical state analysis of the specified region can be realized by using X-ray secondary electron image and micro-area analysis function, which is helpful to optimize the preparation process of photocathodes.
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