Self-sputtering of the Lennard–Jones crystal

Abstract

The self-sputtering yield of the (100) face-centered cubic crystal surface consisting of particles interacting with the Lennard–Jones (LJ) potential is presented as a function of the normalized incident particle kinetic energy for normal incidence. Because the self-sputtering yield depends only on the normalized incident energy, the yield curve presented here is the universal curve, independent of the Lennard–Jones parameters, and therefore serves as the fundamental reference data for the LJ system. The self-sputtering yield data are also compared with experimentally obtained self-sputtering yields of some metals, which shows reasonable agreement at relatively low ion incident energy where mostly deposition occurs. At higher ion energy, the self-sputtering of such an LJ material does not represent those of real solids. This is because the repulsive interactions of the LJ potential do not represent those of actual atoms at short distances. The angle dependence of the self-sputtering yield is also presented for some selected normalized energies.

Why are physical sputtering yields similar for incident ions with different masses?—physical sputtering yields of the Lennard–Jones system

“…The simplicity of the LJ potential function makes it a popular choice to model approximate covalent and metallic bonds as well as van der Waals interactions, as discussed above. It is, however, known that the short-range part of the LJ potential is too repulsive compared with the interatomic potential of real atoms [82,83].…”

“…selfsputtering yield) is defined differently because the incident and surface species cannot be distinguished experimentally. The self-sputtering yield Y self is defined [82] as with N gas all and N in denoting the total number atoms removed or reflected from the material surface and the number of incident ions. It should be noted that, if Y self < 1, the net deposition takes place even if surface atoms are sputtered by ion impact.…”

“…the system of particles interacting with the LJ potential functions, can reproduce the self-sputtering yields of real materials reasonably well except for a high ion-incident-energy range, where the discrepancy between the repulsive potential of the LJ system and those of real atoms becomes significant [82,83]. Therefore, in this study, we extend the LJ-system of a single element used in [82] to that for general sputtering, i.e. the system where the surface material and incident particles are of different species, and compare the sputtering yields of the model system with those of real materials in a relatively low ion-incident-energy range.…”

“…A recent study [82] has shown that the LJ system, i.e. the system of particles interacting with the LJ potential functions, can reproduce the self-sputtering yields of real materials reasonably well except for a high ion-incident-energy range, where the discrepancy between the repulsive potential of the LJ system and those of real atoms becomes significant [82,83].…”

“…As we shall discuss in the following section as well as in appendix A, in this way, we can minimize the number of system parameters while keeping the essential physical mechanisms that govern the sputtering phenomena. Such a system may be considered as a minimal extension of the LJ system of a single element used in [82]. Because the LJ system is one of the most extensively studied models for materials and fluids, determining its sputtering properties may also be considered valuable in itself.…”