Temperature dependence of surface stress across an order-disorder transition:p(1×2)O/W(110)

Abstract

Strain relaxations of a $p(1\ifmmode\times\else\texttimes\fi{}2)$ ordered oxygen layer on W(110) are measured as a function of temperature across the disordering transition using low-energy electron diffraction. The measured strains approach values of 0.027 in the $[1\overline{1}0]$ and $\ensuremath{-}0.053$ in the [001] direction. On the basis of the measured strain relaxations, we give quantitative information on temperature-dependent surface stress using the results of ab initio calculations. From the surface formation energy for different strains, determined by first-principles calculations, we estimate that surface stress changes from $\ensuremath{-}1.1$ for the ordered phase to $\ensuremath{-}0.2\text{ }\text{N}/\text{m}$ for the disordered one along $[1\overline{1}0]$, and from 5.1 to 3.4 N/m along [001]. Moreover, our observation that the strains scale inversely with domain size confirms that the strain relaxation takes place at the domain boundaries.