Networks of Steps on Au and Pt Crystals

TL;DR

This paper models the free energy of step networks on Au and Pt (110) surfaces, predicting their instability and resulting equilibrium shapes, which can be tested through low-temperature crystal shape experiments.

Contribution

A simple theoretical model for the free energy of step networks on Au and Pt surfaces, predicting their stability and equilibrium shapes.

Findings

Networks are predicted to be unstable or metastable against faceting.

Equilibrium shapes feature sharp edges between facets and rounded regions.

Model predictions can be tested through low-temperature crystal shape observations.

Abstract

Networks of steps, seen in STM observations of vicinal surfaces on Au and Pt (110), are analyzed. A simple model is introduced for the calculation of the free energy of the networks as function of the slope parameters, valid at low step densities. It predicts that the networks are unstable, or at least metastable, against faceting and gives an equilibrium crystal shape with sharp edges either between the (110) facet and rounded regions or between two rounded regions. Experimental observations of the equilibrium shapes of Au or Pt crystals at sufficiently low temperatures, i.e. below the deconstruction temperature of the (110) facet, could check the validity of these predictions.