Surfactants in epitaxial growth

TLDR

Epitaxial growth mode depends on the balance of surface, interface, and film free energies, so when material A wets B, B cannot wet A, posing a fundamental obstacle for A/B/A heterostructures. The study proposes using a segregating surfactant to lower surface free energies and suppress island formation, offering a new route to high‑quality microstructures despite thermodynamic constraints. A monolayer of As is employed as a segregating surfactant during Si/Ge/Si(001) growth to reduce surface free energies and suppress island formation. Surfactants can control heteroepitaxial growth, enabling high‑quality microstructures by manipulating surface energetics.

Abstract

We have investigated the role of surface-active species (surfactants) in heteroepitaxial growth. In general, the growth mode is determined by the balance between surface, interface, and film free energies. Thus, if A wets B, B will not wet A. Any attempt at growing an A/B/A heterostructure must overcome this fundamental obstacle. We propose the use of a segregating surfactant to reduce the surface free energies of A and B and suppress island formation, as demonstrated in the growth of Si/Ge/Si(001) with a monolayer of As. Control of growth by amnipulation of surface energetics provides a new avenue to achieve high-quality man-made microstructures against thermodynamic odds.