Ejection of fast recoils under ion bombardment of crystals

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Abstract
Ejection of surface recoils produced by Cu crystal irradiation with 1–40 keV Ar ions has been studied using computer simulation in terms of the atomic chain model. The case where a parallel ion beam bombards a nonvibrating chain at 25° to the chain axis is considered here as example. Only high energy (> 0.2 keV) backsputtered and also backscattered particles are analyzed. It has been found that the main contribution to the flux of backsputtered particles is from the primary and secondary knock-on atoms. The atoms may be ejected in a given direction by various ways whose number is a function of the initial ion energy and ejection angle. The angular and energy distributions of these atoms are pronouncedly anisotropic due, in particular, to the shadowing and focusing effects in scattering of ions and recoils by the chain atoms. The possibility for the particles to be doubly focussed is noted. The results obtained in terms of the two- atomic model are also considered here.