Ultrahigh-resolution scanning microwave impedance microscopy of moire lattices and superstructures

K Lee and MIB Utama and S Kahn and A Samudralas and N Lecontes and BR Yang and SP Wang and K Watanabe and T Taniguchi and MVP Altoe and GY Zhang and A Weber-Bargioni and M Crommie and PD Ashby and J June and F Wang and A Zettl, SCIENCE ADVANCES, 6, eabd1919 (2020).

DOI: 10.1126/sciadv.abd1919

Two-dimensional heterostructures composed of layers with slightly different lattice vectors exhibit new periodic structure known as moire lattices, which, in turn, can support novel correlated and topological phenomena. Moreover, moire superstructures can emerge from multiple misaligned moire lattices or inhomogeneous strain distributions, offering additional degrees of freedom in tailoring electronic structure. High-resolution imaging of the moire lattices and superstructures is critical for understanding the emerging physics. Here, we report the imaging of moire lattices and superstructures in graphene-based samples under ambient conditions using an ultrahigh- resolution implementation of scanning microwave impedance microscopy. Although the probe tip has a gross radius of similar to 100 nm, spatial resolution better than 5 nm is achieved, which allows direct visualization of the structural details in moire lattices and the composite super-moire. We also demonstrate artificial synthesis of novel superstructures, including the Kagome moire arising from the interplay between different layers.

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