Measuring the surface stress polar dependence

TL;DR

This paper introduces a novel experimental method to measure the complete polar dependence of surface stress in crystals, combining electromigration control and AFM measurements to solve for surface stress properties.

Contribution

A new procedure is developed to experimentally determine the full polar dependence of surface stress in crystals, which was previously unavailable.

Findings

First experimental determination of surface stress polar dependence.

Use of electromigration to control surface faceting.

AFM measurements to analyze facet angles and periods.

Abstract

While measurements of the polar dependence of the surface free energy are easily available, measurements of the whole polar dependence of the surface stress of a crystal do not exist. In this paper is presented a new procedure that allows, for the first time, the experimental determination of the surface stress polar dependence of a crystal. For this purpose (1) electromigration is used to control the kinetic faceting of surface orientations that belong to the equilibrium shape of the crystal and (2) for each destabilised surface, the period of faceting as well as the crystallographic angles of the appearing facets are measured by AFM. The so-obtained data lead to a set of equations whose mathematical solution, compatible with physical constraints, gives access to the surface stress polar dependence of the whole crystal and thus to a better understanding of surface stress properties.