Nano-engineering of cesiated chromium surfaces for tailoring electron absorption above work function

Precise work function measurements are important for a variety of physical applications, including control of charge injection/extraction to/from surface adsorbates¹ and thermionics². It is particularly interesting to understand the role of the substrate on the electron reflectivity as function of energy as well as on the work function drop when the substrate is exposed to surface adsorbates like alkali metals (e.g. Cs). In this study, we use low-energy electron microscopy in mirror electron microscopy mode to measure the electron energy dependence of electron reflectivity. By comparing with computed band diagrams, we show how these spectra characterize the surface electronic states of cesiated surfaces. Absorbed current measurements, as function of the electron landing energy, of chromium films oriented on (110) and on (100) planes are compared with their nano-crystalline counterpart. Interestingly, we show that increasing the degree of disorder of the Cr films reduces electron reflectivity independently of the electron energy above the vacuum level.
¹ M. Greiner et al. Nat. Mat. 11, 76 (2012).
² J. W. Schwede et al. Nat. Mat. 9, 762 (2010).