Single indium atoms and few-atom indium clusters anchored onto graphene via silicon heteroatoms

TL;DR

This study demonstrates the controlled self-assembly and stable anchoring of single indium atoms and small clusters on graphene via silicon impurities, revealing their atomic arrangements and dynamic behaviors under electron irradiation.

Contribution

We present a fabrication method for stable indium atoms and clusters on graphene using silicon impurities, with in situ observation of their dynamics under electron beam.

Findings

Single In atoms and clusters depend on Si coordination in graphene.

Structures can transform and move under electron beam irradiation.

No electron-beam induced material modification needed for fabrication.

Abstract

Single atoms and few-atom nanoclusters are of high interest in catalysis and plasmonics, but pathways for their fabrication and stable placement remain scarce. We report here the self-assembly of room-temperature-stable single indium (In) atoms and few-atom In clusters (2-6 atoms) that are anchored to substitutional silicon (Si) impurity atoms in suspended monolayer graphene membranes. Using atomically resolved scanning transmission electron microscopy (STEM), we find that the exact atomic arrangements of the In atoms depend strongly on the original coordination of the Si anchors in the graphene lattice: Single In atoms and In clusters with 3-fold symmetry readily form on 3-fold coordinated Si atoms, whereas 4-fold symmetric clusters are found attached to 4-fold coordinated Si atoms. All structures are produced by our fabrication route without the requirement for electron-beam induced materials modification. In turn, when activated by electron beam irradiation in the STEM, we observe in situ the formation, restructuring and translation dynamics of the Si-anchored In structures: Hexagon-centered 4-fold symmetric In clusters can (reversibly) transform into In chains or In dimers, whereas C-centered 3-fold symmetric In clusters can move along the zig-zag direction of the graphene lattice due to the migration of Si atoms during electron-beam irradiation, or transform to Si-anchored single In atoms. Our results provide a novel framework for the controlled self-assembly and heteroatomic anchoring of single atoms and few-atom clusters on graphene.