Abstract
Single atoms and few-atom nanoclusters are of high interest in catalysis and plasmonics, but pathways for their fabrication and 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 symmetry of the In structures is critically determined by the three- or fourfold coordination of the Si “anchors”. All structures are produced without 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 of the Si-anchored In structures. Our results on In–Si-graphene provide a materials system for controlled self-assembly and heteroatomic anchoring of single atoms and few-atom nanoclusters on graphene.
Highlights
Supported single atoms and atomic clusters comprising only a few atoms (“nanoclusters”) have distinct electrical, optical, magnetic, and catalytic properties
A monolayer chemical vapor deposited (CVD) graphene membrane suspended over a holey SiN chip is first loaded into the scanning transmission electron microscopy (STEM) setup (ultrahigh vacuum (UHV) with base pressure ∼10−9 mbar), which comprises the microscope and directly coupled preparation chambers including laser annealing and an in situ evaporation chamber
The sample is first irradiated in UHV by 600 mW of laser power at 445 nm wavelength, allowing the removal of adventitious hydrocarbon adsorbates from the graphene that stem from membrane fabrication and ambient air exposure.[38,39]
Summary
Supported single atoms and atomic clusters comprising only a few atoms (“nanoclusters”) have distinct electrical, optical, magnetic, and catalytic properties These have suggested single atoms and few-atom clusters to be of high application potential, in heterogeneous catalysis (“singleatom catalysts” to “few-atom catalysts”)[1−4] as well as in nanoplasmonics.[5] For catalysis applications, single atoms and few-atom clusters anchored to carbon substrates are of high relevance.[3,6−11] Shortcomings in fabrication and synthesis, controlled placement and anchoring, and characterization in terms of, e.g., structure, composition, and stability, currently hinder their further study and use. A materials system that intrinsically and readily allows singleatom and few-atom cluster formation and anchoring on graphene membranes in a self-assembled fashion has remained elusive to date
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