Simulation of the nanostructuring of surfaces under ion-beam bombardment

As top-down nanolithography is inexorably approaching its ultimate limits, the techniques based on bottom-up self-assembly become increasingly attractive. Among these, the ion-beam-induced self-assembly of thin films occupies a special place, as they combine both the top-down, focused micro-fabrication with the bottom-up self-assembly nano-processes. Because the ion-beam-induced self-assembly processes are not well understood, here we report on the design-orientated modelling and simulation of quasi-organised metallic nanostructures. It has been found that, because of the near-critical state of the ion-beam-induced self-assembly, the interplay between the angle of ion bombardment, ion flux and substrate temperature leads to nanotopographies that are either quasi-structured or random. Furthermore, minor variations in the angle of bombardment leads to a large variation of the parameters of the nano-organisation, i.e., the type of the ripples - lateral or transversal, and ripple wavelengths. The simulation results were benchmarked against comprehensive experimental results reported in the literature. This study demonstrates that simulation can be used in a feed-forward, design-orientated manner when attempting the fabrication of self-assembled nanostructures with micron-level ion-beam techniques.