Torsional force microscopy of van der Waals moirés and atomic lattices

Journal Article · 04 March 2024 · Proceedings of the National Academy of Sciences of the United States of America

DOI: https://doi.org/10.1073/pnas.2314083121 · OSTI ID:2317702

Pendharkar, Mihir  ^[1]; Tran, Steven J. ^[2]; Zaborski, Jr., Gregory ^[1]; Finney, Joe  ^[2]; Sharpe, Aaron L. ^[3]; Kamat, Rupini V. ^[2]; Kalantre, Sandesh S. ^[2]; Hocking, Marisa ^[1]; Bittner, Nathan J. ^[4]; Watanabe, Kenji  ^[5]; Taniguchi, Takashi ^[6]; Pittenger, Bede ^[7]; Newcomb, Christina J. ^[8]; Kastner, Marc A.  ^[9]; Mannix, Andrew J. ^[1]; Goldhaber-Gordon, David ^[2]

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1. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, Department of Materials Science and Engineering, Stanford University, Stanford, CA 94305
2. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, Department of Physics, Stanford University, Stanford, CA 94305
3. Materials Physics Department, Sandia National Laboratories, Livermore, CA 94550
4. Independent Researcher, Palo Alto, CA 94305
5. Research Center for Electronic and Optical Materials, National Institute for Materials Science, Tsukuba 305-0044, Japan
6. Research Center for Materials Nanoarchitectonics, National Institute for Materials Science, Tsukuba 305-0044, Japan
7. Bruker Nano Surfaces, AFM Unit, Santa Barbara, CA 93117
8. Stanford Nano Shared Facilities, Stanford University, Stanford, CA 94305
9. Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, Department of Physics, Stanford University, Stanford, CA 94305, Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139

In a stack of atomically thin van der Waals layers, introducing interlayer twist creates a moiré superlattice whose period is a function of twist angle. Changes in that twist angle of even hundredths of a degree can dramatically transform the system’s electronic properties. Setting a precise and uniform twist angle for a stack remains difficult; hence, determining that twist angle and mapping its spatial variation is very important. Techniques have emerged to do this by imaging the moiré, but most of these require sophisticated infrastructure, time-consuming sample preparation beyond stack synthesis, or both. In this work, we show that torsional force microscopy (TFM), a scanning probe technique sensitive to dynamic friction, can reveal surface and shallow subsurface structure of van der Waals stacks on multiple length scales: the moirés formed between bi-layers of graphene and between graphene and hexagonal boron nitride (hBN) and also the atomic crystal lattices of graphene and hBN. In TFM, torsional motion of an Atomic Force Microscope (AFM) cantilever is monitored as it is actively driven at a torsional resonance while a feedback loop maintains contact at a set force with the sample surface. TFM works at room temperature in air, with no need for an electrical bias between the tip and the sample, making it applicable to a wide array of samples. It should enable determination of precise structural information including twist angles and strain in moiré superlattices and crystallographic orientation of van der Waals flakes to support predictable moiré heterostructure fabrication.

• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-76SF00515; NA0003525
• OSTI ID: 2317702
• Alternate ID(s): OSTI ID: 2403415
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 10 Vol. 121; ISSN 0027-8424
• Publisher: Proceedings of the National Academy of SciencesCopyright Statement
• Country of Publication: United States
• Language: English