Torsional force microscopy of van der Waals moirés and atomic lattices

Mihir Pendharkar; Steven J. Tran; Gregory Zaborski; Joe Finney; Aaron L. Sharpe; Rupini V. Kamat; Sandesh S. Kalantre; Marisa Hocking; Nathan J. Bittner; Kenji Watanabe; Takashi Taniguchi; Bede Pittenger; Christina J. Newcomb; Marc A. Kastner; Andrew J. Mannix; David Goldhaber-Gordon

doi:10.1073/pnas.2314083121

Article Torsional force microscopy of van der Waals moirés and atomic lattices

Mihir Pendharkar ; Steven J. Tran ; Gregory Zaborski ; Joe Finney ; Aaron L. Sharpe ; Rupini V. Kamat ; Sandesh S. Kalantre ; Marisa Hocking ; Nathan J. Bittner ; Kenji Watanabe (National Institute for Materials Science) ; Takashi Taniguchi (National Institute for Materials Science) ; Bede Pittenger ; Christina J. Newcomb ; Marc A. Kastner ; Andrew J. Mannix ; David Goldhaber-Gordon

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Mihir Pendharkar, Steven J. Tran, Gregory Zaborski, Joe Finney, Aaron L. Sharpe, Rupini V. Kamat, Sandesh S. Kalantre, Marisa Hocking, Nathan J. Bittner, Kenji Watanabe, Takashi Taniguchi, Bede Pittenger, Christina J. Newcomb, Marc A. Kastner, Andrew J. Mannix, David Goldhaber-Gordon. Torsional force microscopy of van der Waals moirés and atomic lattices. Proceedings of the National Academy of Sciences. 2024, 121 (10), e2314083121. https://doi.org/10.1073/pnas.2314083121

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Moiré superlattices formed in twisted Van der Waals’ materials have unlocked a new degree of freedom hitherto absent in condensed matter. Yet, techniques for precise, rapid and reliable imaging of the moir ́es formed have remained scarce. In this work, we demonstrate the use of Torsional Force Microscopy, a scanning probe technique that is sensitive to local dynamic friction and reveals the moir ́es formed between bi-layers of graphene and between graphene and hBN. Additionally, this technique has also been successful in imaging the atomic lattice of graphene and hBN. In TFM, the AFM cantilever is actively driven at one of its torsional resonance similar to non-contact AFM and a feedback loop maintains a constant vertical loading force, similar to contact AFM, controlling the interaction between the tip and the sample. By tracking the amplitude and phase of the driven torsional resonance, using the lateral signal from the photo detector, patterns consistent with both moir ́es and atomic lattices are routinely observed. Low loading forces are sensitive to moir ́es near the surface, while increased forces reveal buried moir ́es. TFM does not require an electrical bias between the tip and the sample, providing non-perturbative analysis with a high degree of repeatability across a wide variety 2D materials’ crystal lattices and moir ́es of their heterostructures, in operando.

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