Orientation dependence of the Cu(001) surface step stiffness: Failure of solid-on-solid and Ising models to describe experimental data

Abstract

We have investigated the step stiffness on Cu(001) surfaces as a function of step orientation by two independent methods at several temperatures near 300 K. Both sets of data agree well and show a substantial dependence of the stiffness on the angle of orientation. With the exception of steps oriented along ?110?, the experimental stiffness is significantly larger than the stiffness calculated within the solid-on-solid model and the Ising model, even if next-nearest-neighbor interactions are taken into account. Our results have considerable consequences for the understanding and for the theoretical modeling of equilibrium and growth phenomena, such as step meandering instabilities.