Above: Experimental Conditions for Hydrogen Abstraction. a) Schematic showing the setup. Both probe and sample are Si(100). The probe is hydrogenated, while the sample is unpassivated to enable molecule adsorption. The sample has a sparse coverage of tall molecules (EAOGe-C2I). The x- and y-axes are used to laterally align a molecule with a target location on the build site, while the z-axis can adjust the separation between probe and sample, enabling the reaction to proceed. b-d) Zoom-in on the atomic configuration at the site of the reaction. Initially, the molecule is lined up with an atomic site on the probe apex (b); the molecule then approaches the targeted hydrogen atom until the reaction proceeds (c); finally, the molecule retracts, taking the hydrogen atom with it (d). Insets in (b) and (d) show inverted-mode STM images before and after H-abstraction. e) Potential energy of the system, calculated by density functional theory, as a function of the distance between the hydrogen atom and its host silicon atom, for two different separations of probe and sample (see Methods and Supplementary Section 2). For larger separation (triangles), the barrier to hydrogen transfer is about 1.2 eV . At a critical separation (squares), the reaction becomes barrierless. The black arrow represents the energetically downhill hydrogen transfer from the probe apex to the molecule and the green arrow indicates the retraction.
A Happy New Year for sure.
A new and innovative way to do scanning tunneling microscopy. And repeatable and controllable subtractive mechanosynthesis off a silicon surface under zero bias with a molecular tool based on a design approach developed a long number of years ago for the task. And the writing team threaded a narrow needle of depth and clarity perfectly.
https://arxiv.org/abs/2512.24431
Something wonderful. And the first big/very small step.
Authors: Eduardo Barrera, Bheeshmon Thanabalasingam, Rafik Addou, Damian Allis, Aly Asani, Jeremy Barton, Tomass Bernots, Brandon Blue, Adam Bottomley, Doreen Cheng, Byoung Choi, Megan Cowie, Chris Deimert, Michael Drew, Mathieu Durand, Tyler Enright, Robert A. Freitas Jr., Alan Godfrey, Ryan Groome, Si Yue Guo, Sheldon Haird, Aru Hill, Taleana Huff, Christian Imperiale, Alex Inayeh, Jerry Jeyachandra, Mark Jobes, Matthew Kennedy, Robert J. Kirby, Mykhaylo Krykunov, Sam Lilak, Hadiya Ma, Adam Maahs, Cameron J. Mackie, Oliver MacLean, Michael Marshall, Terry McCallum, Ralph C. Merkle, Mathieu Morin, Jonathan Myall, Alexei Ofitserov, Sheena Ou, Ryan Plumadore, Adam Powell, Max Prokopenko, Henry Rodriguez, Sam Rohe, Luis Sandoval, Marc Savoie, Khalil Sayed-Akhmad, Ben Scheffel, Tait Takatani, D. Alexander Therien, Finley Van Barr, Dusan Vobornik, Janice Wong, Reid Wotton, Ryan Yamachika, Cristina Yu, Marco Taucer
Abstract: Scanning Tunneling Microscopy (STM) enables fabrication of atomically precise structures with unique properties and growing technological potential. However, reproducible manipulation of covalently bonded atoms requires control over the atomic configuration of both sample and probe – a longstanding challenge in STM. Here, we introduce inverted-mode STM, an approach that enables mechanically controlled chemical reactions for atomically precise fabrication. Tailored molecules on a Si(100) surface image the probe apex, and the usual challenge of understanding the probe structure is effectively solved. The molecules can also react with the probe, with the two sides of the tunnel junction acting as reagents positioned with sub-angstrom precision. This allows abstraction or donation of atoms from or to the probe apex. We demonstrate this by using a novel alkynyl-terminated molecule to reproducibly abstract hydrogen atoms from the probe. The approach is expected to extend to other elements and moieties, opening a new avenue for scalable atomically precise fabrication.
