Rotational epitaxy of periodic overlayers

Abstract

Rotational epitaxy refers to the alignment of a solid overlayer along a specific orientation relative to the substrate. Rotational epitaxy along nonsymmetry orientations represent an important alternative to pseudomorphic strain or misfit dislocations for the accommodation of lattice misfit in epitaxial thin films. In this study, the orientations of possible epitaxial overlayers which are periodic relative to the substrate are examined over a wide range of overlayer and substrate lattice mismatch. Both square and hexagonal lattice structures are considered. By comparing the relative orientation and lattice mismatches of periodic overlayers, sets of related structures are observed. The rules which define the relationships between periodic structures in each set can be demonstrated using geometrical models. The results provide a unique insight into the observations of rotational epitaxy in rare gas layers physisorbed on graphite and alkali metals chemisorbed on metals.