Tip-induced chemistry and electron spin resonance atomic force microscopy

Dr. Lisanne Sellies

Post-doc at IBM Research Zurich

Abstract

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Scanning tunneling microscopy (STM) and atomic force microscopy (AFM) provide unique access to individual molecules. Combining atomic-scale imaging and atomically precise manipulation, these techniques enable the controlled synthesis of new molecular species and the investigation of their physical and chemical properties at the single-molecule level. After introducing the principles of STM and AFM, I will present our recent investigations of cyclocarbons and introduce our recently developed technique for measuring electron spin resonance (ESR) signals with an AFM. Cyclocarbons, molecular rings of carbon atoms, have been synthesized on surfaces using tip-induced chemistry [1-3], and the formation of larger cyclocarbons by dimerization of precursors was shown [3,4]. Cyclocarbons are fundamentally important for testing theoretical models. In this talk, I will show that we can synthesize large cyclocarbons by fusing multiple cyclocarbons using atom manipulation with an STM [5]. We studied the aromaticity of the formed cyclocarbons and experimentally demonstrate that effects of aromaticity persist for ring sizes of 42 carbon atoms [5]. In the second part of the presentation, I will discuss our recently developed ESR-AFM technique, which enables the measurement of ESR signals from individual molecules using an AFM [6]. Our ESR-AFM spectra measured on single pentacene molecules feature sub-nanoelectronvolt energy resolution, allowing us to distinguish between molecules that only differ in their isotopic configuration. Moreover, the electron spins of pentacene can be coherently manipulated over timescales of tens of microseconds [6]. The high energy resolution and long spin coherence represent a leap forward for local studies of future artificial quantum systems and local quantum-sensing experiments. [1] K. Kaiser#, L. M. Scriven# et al., Science 365, 1299-1301 (2019). [2] L. Sun#, W. Zhen# et al., Nature 623, 972-976 (2023). [3] F. Albrecht#, I. Rončević#, Y. Gao#, F. Paschke# et al., Science 384, 677-682 (2024). [4] Y. Guo et al., Nat. Commun. 16, 11507 (2025). [5] L. Sellies#, M. Vitek#, Y. Gao#, F. Paschke# et al., arXiv arXiv:2603.02040 (2026). [6] L. Sellies et al., Nature 624, 64-68 (2023).