Energy Distribution in Field Emission from Krypton Covered Tungsten

Abstract

Work functions and energy distributions as functions of relative coverage have been obtained for Kr adsorbed on the (110), (100), (111), and (112) planes of a tungsten field emitter, from zero coverage to several monolayers. Work function results agree with previous measurements where overlap exists. The data could be fitted by the Topping equation for depolarization, yielding polarizabilities in reasonable agreement with the atomic value if HCP monolayer densities were used, on all but the (110) plane where a higher value resulted. Energy distribution in the submonolayer range show no deviations from free-electron-like behavior, except possibly on the (110) plane where a strong antiresonance seems to occur. On the (100) surface the Swanson anomaly found in the distribution from the clean surface decreases monotonically with Kr coverage, indicating that it is probably due to surface states. Work function values in the multilayer range can be interpreted to mean that the conduction band of Kr lies ∼ 1.4 eV below the vacuum. Energy distributions for multilayers deviate from free-electron-like behavior; both electric and inelastic scattering processes could explain this result.