Physical and Chemical Roughness of Alkali-Animonide Cathodes

Over the last decade, alkali-antimonides have been investigated as high QE cathodes in green light and more recently as ultra-low intrinsic emittance cathodes in nearthreshold red wavelengths at cryogenic temperatures [1]. Nano-meter scale surface non-uniformities (physical roughness and chemical roughness or work function variations) are thought to limit the smallest possible emittance from these materials at the photoemission threshold under cryogenic conditions [2]. Despite this, the surfaces of alkali antimonides have not been well characterized in terms of the surface non-uniformities. Here, we present measurements of surface non-uniformities of alkali-antimonide thin films using several surface characterization techniques like atomic force microscopy, kelvin probe force microscopy, low energy electron microscopy and near-threshold photoemission electron microscopy. This helps show how such non-uniformities limit the intrinsic emittance.