Dependence on size and curvature of sputtering yield in nanowires

Abstract

Bombardment of different <110> Co nanowires with 1-k eV argon ions along a <100> direction is simulated by molecular dynamics. Sputtering yield is analysed for different surface curvatures. For that purpose, results on three cross-section shapes were obtained, namely: circular, square and rhomboid. A low dose is used to avoid great surface damage. Yield increases with increasing curvature. However, if the cross-section size decreases, this dependence is modified and other phenomena such as spike sputtering occur. In particular, this effect causes an abundant sputtering. The Sigmund theoretical model was used to compare predictions. Results for sputtering yield show a maximum and an asymptotic behaviour for large nanowire sizes. These asymptotic values confirm the dependence on curvature. This dependence for small sizes differs from the simulation model. The Sigmund model does not take into account the local heating, besides it assumes that the energy deposition profile does not depend on target size. The angular distributions of the speed vector show that the lattice structure determines the directions of ejection, and therefore, this structure would also influence the sputtering yield.