The physics and applications of ion beam erosion

Abstract

Energetic ion bombardment of solid targets can lead to the production of atomic recoils and defects within the solid and the ejection or sputtering of atoms from the surface with the consequent erosion of the solid. The yield of sputtered atoms per ion depends on a number of ion and target parameters but, particularly, on the gradient of the surface with respect to the incident ion flux, the surface curvature and higher spatial derivatives of the height. As a result of these dependences of the local erosion rate, the morphology of a surface can be modified. But, in addition, surface atomic relaxation effects which may be mediated by the irradiation can occur and so the evolution of the surface may be complex. If the nature of these, often competing, processes is understood and can be suitably controlled by selection of experimental conditions, ion beam erosion can be employed to generate useful surface geometries. This review briefly summarizes current understanding of the sputtering process and the origin of the above dependences and describes how, if only a surface gradient related mechanism dominates, the evolution of surface geometry can be accurately predicted. The higher-order and surface relaxation processes are then considered in both a deterministic approach and in a stochastic approach and these are shown to lead to fine spatial scale modifications to evolving surfaces. In both these areas, the physical models are supported by experimental observations. It is then shown how the lowest and higher orders and competing mechanisms can be selected in order to produce the desired surface morphologies in several application areas, including depth profiling of impurities in solids, ion milling and polishing, and the creation of repetitive surface structures.

Self-organized nanopatterning of silicon surfaces by ion beam sputtering

“…Note that the BH approach predicted pattern formation for all incidence angles, in particular at normal incidence. Thus, it became evident that pattern formation in silicon surfaces below the critical angle (around 48 for low-energy Ar þ bombardment [37,38]) was in fact triggered by the incorporation of impurities during the process. One example that clearly shows the change of mind caused on the researchers by this new scenario is the statement by Macko et al in 2011 [33] concerning pattern observation for u < 45 : ''All patterns observed in this angular range -in the past, often erroneously interpreted in terms of pure ion beam erosion mechanisms -are just a consequence of unintentional co-deposition of a non-volatile species during erosion, resulting in a two-component surface system''.…”

Ion-Beam Sculpting Time Scales

“…3. Sputter erosion is assumed to contribute a constant radial hole opening rate of 1:06 10 ÿ2 nm=Ar nm ÿ2 since the sputter yields of SiO 2 and SiN are very similar [18], weakly flux dependent [19], and presumed to be independent of duty cycle. In conclusion, we have shown that the dynamics of hole closing in SiO 2 and SiN are strongly dependent on the rest time between ion beam pulses, implying that a significant amount of hole closing occurs when no beam is incident on the material surface.…”

Propulsion of Ripples on Glass by Ion Bombardment

“…DOI: 10.1103/PhysRevLett.96.107602 PACS numbers: 79.20.Rf, 61.80.Az, 68.35.Ct, 81.16.Rf Modification of surfaces is a widely explored and technologically highly relevant field of research. Surfaces bombarded by a beam of ions erode, but they may also develop specific nanoscale geometrical patterns [1]. These patterns have been studied intensively because they reveal details in the interaction of energetic particles with matter and because they have implications for ion-beam sputter erosion and deposition [2].…”