Reconstruction changes drive surface diffusion and determine the flatness of oxide surfaces

TL;DR

This study investigates how surface reconstructions driven by oxygen chemical potential influence surface diffusion and flatness of oxide surfaces, revealing thermodynamics as the key factor in surface mass transport at the atomic scale.

Contribution

It provides new phenomenological insights linking surface reconstruction, oxygen chemical potential, and surface diffusion on oxide materials at the atomic level.

Findings

Surface reconstruction stability depends on oxygen chemical potential.

Higher oxygen potential promotes surface flattening and diffusion.

Thermodynamics governs surface diffusion more than kinetics.

Abstract

Surface diffusion on metal oxides is key in many areas of materials technology, yet it has been scarcely explored at the atomic scale. This work provides phenomenological insights from scanning tunneling microscopy on the link between surface diffusion, surface atomic structure, and oxygen chemical potential based on three model oxide surfaces: Fe$_2$O$_3(1\overline{1}02)$, La$_{1-x}$Sr$_x$MnO$_3$(110), and In$_2$O$_3$(111). In all instances, changing the oxygen chemical potential used for annealing stabilizes reconstructions of different compositions while promoting the flattening of the surface morphology -- a sign of enhanced surface diffusion. It is argued that thermodynamics, rather than kinetics, rules surface diffusion under these conditions: The composition change of the surface reconstructions formed at differently oxidizing conditions drives mass transport across the surface.