Erosion of solid neon by keV electrons

The erosion of solid neon by keV electrons has been studied experimentally and theoretically. Electronic sputtering as well as temperature-enhanced sublimation are investigated by a frequency-change measurement on a quartz crystal or in some cases by the change in intensity of reflected electrons. The erosion yield increases with increasing temperature for substrate temperatures above 7K. Below this temperature sputtering via electronic transitions is the dominant process. The yield shows a clear minimum for film thicknesses about (5-7)×1016 Ne atoms/cm2 for 2-keV electrons. The sputtering yield for thick films has a maximum at 1.2-1.5 keV. The results are explained by the diffusion of excitations to the surface with subsequent decay. From this model and the experimental results one derives a characteristic diffusion length of about 1×1017 Ne atoms/cm2. The eventual particle ejection is driven by decay of surface-trapped excitons or by dissociative recombination. The magnitude of the yield indicates that deexciting neon particles at the surface induce further sputtering. Direct sputtering from electron-nucleus collisions does not contribute significantly to the yield