Speaker
Description
Direct 3D manipulation of covalently bonded atoms remains a challenge for atomically precise fabrication. Here, we introduce inverted-mode scanning tunnelling microscopy (IM-STM) [1] as a new approach for controlled atomic-scale reactions and demonstrate its application to individual silicon atom abstraction under ultra-high vacuum and cryogenic conditions. A silicon probe chip (SPC) with an atomically clean Si(100)-2x1 crystalline terrace at the apex serves as the probe, while a silicon wafer bearing isolated, custom-synthesized, surface-bound molecular tools acts as the sample. These molecular tools function both as imaging agents and as tools for chemical manipulation in a mechanosynthesis-based process. As the sample is scanned with the SPC, each protruding molecule provides a mirror image of the probe apex, and can immediately participate in surface reactions, enabling rapid verification and repeatability. For subtractive silicon patterning we employ MAOC-C2I , a tripodal molecule featuring an ethynyl iodide (-C2I) functional group. After electrical bias pulse-induced cleavage of the iodine, the resulting C2 radical is aligned with a target Si(100)-2x1 dimer of the SPC. A controlled approach-retraction process transfers one silicon atom to the molecule, akin to “pick-and-place” fabrication. This leaves unique silicon vacancies at the target site, which we describe with IM-STM imaging and density functional theory (DFT) calculations. Imaging with new molecules elsewhere on the sample surface confirms changes to the SPC lattice, and allows iterative targeting for the next abstraction, thus enabling a new capability towards atomically precise fabrication, and general manipulation of covalently-bonded silicon atoms in 3D.
- Barrera, E. et al. Inverted-Mode Scanning Tunneling Microscopy for Atomically Precise Fabrication. arXiv (2025) doi:10.48550/arxiv.2512.24431.
| Keyword-1 | Scanning Tunneling Microscopy |
|---|---|
| Keyword-2 | Silicon Abstraction |
| Keyword-3 | Atomically Precise Fabrication |