Abstract
Analysis, presented in this work, shows that a considerable amount of experimental data on energy spectra and yield of sputtered neutral atoms, ejected from transition metals under bombardment by ions of energies of 102–103 eV, is in satisfactory agreement with a description of the sputtering process within the framework of the simple model in which atomic collisions are considered as the collisions of absolutely elastic hard spheres. A new method, based on this conclusion, allowing to obtain information about a relative role of different mechanisms of the secondary ion emission (SIE) which are distinguished by its sensitivity to the kinetic energy changes of the bombarding ions, has been proposed. The investigation of energy spectra of sputtered ions, ejected from Ta, Nb, V and Mo under bombardment by Hg+ ions of energies from 250 up to 2000 eV has been performed with the purpose of elucidating (by the proposed method) the mechanism of secondary ion emission. The experiments have been carried out under ultra-high vacuum conditions with control of the necessary purity of the surface under investigation. The SIE mechanism during Ta, Nb and Mo sputtering is shown to be determined by the electron exchange between a sputtered atom and a metal, and independent of the primary ion energy. In the case of vanadium a mechanism sensitive to the kinetic energy of the primary ions is added to the mentioned one. The experimentally obtained energy dependence of the ionization degree of sputtered atoms is compared with those predicted by different theories.
Published Version
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