Pinhole-seeded lateral epitaxy and exfoliation of GaSb films on graphene-terminated surfaces

TL;DR

This study reveals that GaSb films grow on graphene-terminated surfaces via seeded lateral epitaxy at pinhole defects, enabling exfoliation of free-standing membranes and offering a general approach for epitaxy on 2D materials.

Contribution

It demonstrates a new mechanism of seeded lateral epitaxy driven by pinhole defects, challenging the necessity of remote interactions in epitaxial growth on graphene.

Findings

GaSb grows via seeded lateral epitaxy on graphene with pinholes.

Exfoliation of free-standing GaSb membranes is possible.

Controlled defect introduction influences epitaxial growth and membrane properties.

Abstract

Remote epitaxy is a promising approach for synthesizing exfoliatable crystalline membranes and enabling epitaxy of materials with large lattice mismatch. However, the atomic scale mechanisms for remote epitaxy remain unclear. Here we experimentally demonstrate that GaSb films grow on graphene-terminated GaSb (001) via a seeded lateral epitaxy mechanism, in which pinhole defects in the graphene serve as selective nucleation sites, followed by lateral epitaxy and coalescence into a continuous film. Remote interactions are not necessary in order to explain the growth. Importantly, the small size of the pinholes permits exfoliation of continuous, free-standing GaSb membranes. Due to the chemical similarity between GaSb and other III-V materials, we anticipate this mechanism to apply more generally to other materials. By combining molecular beam epitaxy with \textit{in-situ} electron diffraction and photoemission, plus \textit{ex-situ} atomic force microscopy and Raman spectroscopy, we track the graphene defect generation and GaSb growth evolution a few monolayers at a time. Our results show that the controlled introduction of nanoscale openings in graphene provides a powerful route towards tuning the growth and properties of epitaxial films and membranes on 2D materials.