Hydro-dynamics of surface patterning by ion beam irradiation: an interface phenomenon

TL;DR

This paper investigates how ion beam-induced flow within amorphous layers causes surface patterning, emphasizing the dominant role of the amorphous/crystalline interface over surface erosion effects, supported by experimental and theoretical analysis.

Contribution

It introduces a new understanding of surface patterning driven by interface phenomena and models the process using Navier-Stokes flow coupled with the Exner equation.

Findings

Interface-driven patterning dominates over surface erosion effects.

The amorphous/crystalline interface controls surface morphology changes.

Theoretical model successfully explains experimental observations.

Abstract

We show that the ion beam induced incompressible amorphous solid flow in terms of advection transport mechanism leads to the erosion and deposition of atoms at the amorphous/crystalline (a/c) interface resulting in the formation of pattern at the a/c interface as well as at the free surface. The ion beam impact generated erosion and mass redistribution at the free surface are found to have insignificant effect in patterning of surface. By varying the thicknesses of amorphous layer, it has been established that a/c interface plays the dominant role in surface patterning. The morphological variation of Si surface after 50 keV Ar+ ion bombardment has been investigated by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (X-TEM) as a function of ion fluence. Navier-Stokes flow inside the amorphous layer coupled with the Exner equation successfully explains the growth mechanism of surface patterning.