Erosion of solid neon by keV electrons

Abstract

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 7 K. Below this temperature sputtering via electronic transitions is the dominant process. The yield shows a clear minimum for film thicknesses about (5--7)\ifmmode\times\else\texttimes\fi{}${10}^{16}$ Ne atoms/${\mathrm{cm}}^{2}$ 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\ifmmode\times\else\texttimes\fi{}${10}^{17}$ Ne atoms/${\mathrm{cm}}^{2}$. 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.