Solid flow drives surface nanopatterning by ion-beam irradiation

TL;DR

This paper investigates how ion-beam irradiation induces surface nanopatterning on silicon by revealing that a highly viscous, nanoscopically thin surface layer flows under stress, leading to self-organized patterns.

Contribution

It provides experimental validation for a hydrodynamic model describing surface flow and nanopattern formation during ion-beam sputtering.

Findings

Validated hydrodynamic model predictions

Identified flow of a viscous surface layer driven by ion-beam stress

Linked slow relaxation to defect dynamics in the surface layer

Abstract

Ion Beam Sputtering (IBS) is known to produce surface nanopatterns over macroscopic areas on a wide range of materials. However, in spite of the technological potential of this route to nanostructuring, the physical process by which these surfaces self-organize remains poorly under- stood. We have performed detailed experiments of IBS on Si substrates that validate dynamical and morphological predictions from a hydrodynamic description of the phenomenon. Our results elucidate flow of a nanoscopically thin and highly viscous surface layer, driven by the stress created by the ion-beam, as a description of the system. This type of slow relaxation is akin to flow of macroscopic solids like glaciers or lead pipes, that is driven by defect dynamics.