Epitaxial Growth of Cesium Potassium Antimonide Semiconductor Photocathode

Semiconductor photocathodes are key for the fast development of electron accelerators and photon detectors. Polycrystalline photocathode or photocathodes having intrinsic surface disorder do limit for high brightness electron beam. Growing epitaxial photocathodes have potential to solve this problem and achieve high brightness electron beam. This abstract demonstrates the synthesis of thin films of K₂CsSb, where K₂CsSb have been grown epitaxially on different single crystal substrates. Streaky pattern in RHEED confirms epitaxial growth with smooth surface and provide crystalline structural details. RHEED also provides azimuthal angular dependence crystalline structure of K₂CsSb thin film. Epitaxially grown 20 nm film thickness provides QE of about 4.5% at wavelength 530 nm light, where thickness has been determined using XRR. XRR also confirms formation of smooth K₂CsSb thin film. XRD at Bragg condition provides information about mosaicity and strain from sample. XRD also provides information about grain size calculated value of which is way larger than film thickness. Azimuthal angular dependence of the crystalline structure of the film is also found from XRD. XRF affirms stoichiometry of K₂CsSb. QE about 9.5% at 530 nm has been achieved with a high enough thickness of epitaxial K₂CsSb photocathode thin film.