Realization of AlSb in the double layer honeycomb structure: a robust new class of two-dimensional material

TL;DR

This paper reports the successful synthesis and characterization of a novel two-dimensional AlSb material with a double-layer honeycomb structure, revealing unique electronic properties and expanding the family of 2D vdW semiconductors.

Contribution

First experimental realization of a stable 2D AlSb in the double-layer honeycomb structure using molecular beam epitaxy.

Findings

2D AlSb has a bandgap of 0.93 eV, smaller than bulk AlSb.

Successful growth of AlSb in DLHC structure confirmed by microscopy.

InSb DLHC structure was not stable and formed bulk islands.

Abstract

Exploring new two-dimensional (2D) van der Waals (vdW) systems is at the forefront of materials physics. Here, through molecular beam epitaxy on graphene-covered SiC(0001), we report successful growth of AlSb in the double-layer honeycomb (DLHC) structure, a 2D vdW material which has no direct analogue to its 3D bulk and is predicted kinetically stable when freestanding. The structural morphology and electronic structure of the experimental 2D AlSb are characterized with spectroscopic imaging scanning tunneling microscopy and cross-sectional imaging scanning transmission electron microscopy, which compare well to the proposed DLHC structure. The 2D AlSb exhibits a bandgap of 0.93 eV versus the predicted 1.06 eV, which is substantially smaller than the 1.6 eV of bulk. We also attempt the less-stable InSb DLHC structure; however, it grows into bulk islands instead. The successful growth of a DLHC material here opens the door for the realization of a large family of novel 2D DLHC traditional semiconductors with unique excitonic, topological, and electronic properties.