Speaker
Description
Atomically Precise Fabrication (APF) is the creation of covalently-bonded structures through addition, subtraction, or manipulation of atoms or small molecules. Our approach to APF is Inverted-Mode Scanning Tunneling Microscopy (IM-STM), a mechanosynthesis-based technique that uses tailored 3D molecules deposited on a sample to scan and react with a flat, crystalline probe, enabling reagent transfer to and from the probe apex with sub-angstrom precision.[1,2]
Here, we demonstrate the transfer of C2H and C2H2 on a Si(100):H probe apex and present a novel method of determining product atomic configurations. On-surface, covalently bound C2H and C2H2 were created from the reaction of dangling bond (DB) patterns on the probe with custom 3D molecules (EAOGe-C2I) presenting either an upright C2 or C2H moiety, or “feedstock”. As these products fall outside of the limits of detection of most on-surface spectroscopic methods, we developed a method that leverages established radical chemistry trends to determine the atomic configurations of the products.
By varying DB patterning, targeting, and trajectory, transferred feedstock can form singly-bound C2H, C2 + dihydride, and on- and inter-dimer C2H2 products on the probe. Product atomic configurations were determined by interconverting the products using mechanosynthetic reactions, supported by DFT and DFTB+ simulations. Mechanistic hypotheses suggest that mid-trajectory hydrogen tunneling plays a role in reaction selectivity.
Our ability to positionally control feedstock transfers and perform sub-monolayer characterization represents a significant advancement in APF, opening new avenues for development of complex structures at the atomic scale.
Track: Surface Science
Keywords: Atomically precise fabrication, STM, Semiconductors
[1] T. Huff et al., “Molecular tools for non-planar surface chemistry,” arXiv:2508.16798 [cond-mat.mtrl-sci] (2025), https://doi.org/10.48550/arXiv.2508.16798 (submitted for peer review).
[2] E. Barrera et al., “Inverted-mode scanning tunneling microscopy for atomically precise fabrication,” arXiv:2512.24431 [cond-mat.mes-hall] (2025), https://doi.org/10.48550/arxiv.2512.24431 (submitted for peer review).
| Keyword-1 | Atomically precise fabrication |
|---|---|
| Keyword-2 | STM |
| Keyword-3 | Semiconductors |