Self-assembled in-plane Ge nanowires on rib-patterned Si (1 1 10) templates

Abstract

Ge heteroepitaxy on Si (1 1 10) substrates induces the formation of prism-shaped in-plane nanowires bounded with ${1\phantom{\rule{4pt}{0ex}}0\phantom{\rule{4pt}{0ex}}5}$ facets. In this work, in-plane nanowires were fabricated via the growth of Ge onto rib-patterned Si (1 1 10) templates oriented in the $[55\overline{1}]$ direction. Atomic force microscopy (AFM) reveals that a self-elongation of the nanowires occurs, resembling the phenomena observed on rib-patterned Si (0 0 1) templates, which indicates that this is a universal effect for nanowires grown on rib patterns. Finite-element simulations, performed with input from the latest ab initio calculations, reveal that the mechanism behind these phenomena is the minimization of the total energy density of the epilayer under rib-dominated geometry. Ge surface diffusion leads to a broadening of the Ge nanowires at the rib shoulder sites, which is proved to be an effective route to reduce the total energy density. Our results provide a straightforward solution for the realization of a single or a few Ge nanowires for potential device applications.