Dresden 2026 – scientific programme

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O: Fachverband Oberflächenphysik

O 56: Scanning probe techniques: Method development II

O 56.6: Talk

Wednesday, March 11, 2026, 11:45–12:00, HSZ/0401

Atomically Precise Si Abstraction by Inverted-Mode STM — •Rosemary Cranston, Zehra Ahmed, Eduardo Barrera, Brandon Blue, Adam Bottomley, Christian Imperiale, Alex Inayeh, Mathieu Morin, Marco Taucer, and Bheeshmon Thanabalasingam — CBN Nano Technologies Inc., Ottawa, Canada

Direct 3D manipulation of covalently bonded atoms remains a challenge for atomically precise fabrication. Here, we introduce inverted-mode scanning tunneling microscopy (STM) as a new approach for controlled atomic-scale reactions and demonstrate its application to individual Si atom abstraction. A Si probe chip (SPC) with an atomically clean Si(100)-2x1 crystalline terrace at the apex serves as the probe, while a Si wafer bearing isolated, custom-synthesized, surface-bound molecular tools act as the sample. These molecules function both as imaging agents and as tools for chemical manipulation. 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. For subtractive Si patterning, we employ tripodal molecules featuring an ethynyl iodide moiety. After bias-induced cleavage of the iodine, the resulting radical is aligned with a target Si dimer of the SPC. A controlled approach-retraction process transfers a Si atom to the molecule, leaving unique Si vacancies at the target site. Imaging with new iodinated molecules elsewhere on the sample surface confirms changes to the SPC lattice, and allows iterative targeting for the next abstraction, thus enabling a new method for atomically precise fabrication, and the manipulation of Si atoms in 3D.

Keywords: Scanning tunneling microscopy; Silicon abstraction; Atomically precise fabrication; Density functional theory; Mechanosynthesis