High photoemission efficiency of submonolayer cesium-covered surfaces

Abstract

Long‐wavelength photoemission current from Cs and O₂ coadsorbed W (100) surfaces has been measured as a function of the amount of Cs and O₂ deposition. Auger, work‐function, and LEED measurements were used to monitor the exact amount of Cs and O₂. We found that for different initial oxygen exposure a distinct maximum of photoemission efficiency exists at Cs coverage of φ_Cs=0.229±0.3 (2.9×10¹⁴ Cs atoms/cm²), which is near but not at the well‐known work‐function minimum (φ_Cs=0.25). The maximum photocurrent increases as the initial oxygen exposure increases. At optimum peak, the photoemission efficiencies are typically three to five times that of other Cs and O₂ coverages.