Elastic-displacement field of an isolated surface step.

Abstract

The asymptotic elastic-displacement field of a surface step is shown to result from a planar force distribution which is composed of two point elastic dipoles, one oriented along the surface of arbitrary magnitude and one normal to the surface with dipole moment [ital ag] where [ital a] is the step height and [ital g] is the surface stress. The analytic form of the dipole displacement field for an isotropic material is presented. Experimental and simulated TEM images of the asymptotic displacement field are presented which demonstrate the dipolar nature of the force distribution. The normal dipole moment of a monatomic step on Si(111)(7[times]7) is computed to be 0.58[plus minus]0.04 eV/A. The tangential dipole moment is measured to be 1.46[plus minus]0.3 eV/A. The stress and strain tensors for an isolated step and the displacement field for a stepped surface are presented.