Torsional force microscopy of van der Waals moirés and atomic lattices

• 成果类型: Article
• 署名作者: Pendharkar, Mihir; Tran, Steven J.; Zaborski, Gregory, Jr.; Finney, Joe; Sharpe, Aaron L.; Kamat, Rupini V.; Kalantre, Sandesh S.; Hocking, Marisa; Bittner, Nathan J.; Watanabe, Kenji; Taniguchi, Takashi; Pittenger, Bede; Newcomb, Christina J.; Kastner, Marc A.; Mannix, Andrew J.; Goldhaber-Gordon, David
• 署名单位: Stanford University; United States Department of Energy (DOE); SLAC National Accelerator Laboratory; Stanford University; Stanford University; United States Department of Energy (DOE); Sandia National Laboratories; National Institute for Materials Science; National Institute for Materials Science; Stanford University; Massachusetts Institute of Technology (MIT)
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-9142
• DOI: 10.1073/pnas.2314083121
• 发表日期: 2024-03-05
• 关键词: angle

摘要

In a stack of atomically thin van der Waals layers, introducing interlayer twist creates a moir & eacute; 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 moir & eacute;, 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 moir & eacute;s 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 moir & eacute; superlattices and crystallographic orientation of van der Waals flakes to support predictable moir & eacute; heterostructure fabrication.