title: Evolution of Moiré Profiles from van der Waals Superstructures of Boron Nitride Nanosheets.
abstract: Two-dimensional (2D) van der Waals (vdW) superstructures, or vdW solids, are formed by the precise restacking of 2D nanosheet lattices, which can lead to unique physical and electronic properties that are not available in the parent nanosheets. Moiré patterns formed by the crystalline mismatch between adjacent nanosheets are the most direct features for vdW superstructures under microscopic imaging. In this article, transmission electron microscopy (TEM) observation of hexagonal Moiré patterns with unusually large micrometer-sized lateral areas (up to ~1 μm(2)) and periodicities (up to ~50 nm) from restacking of liquid exfoliated hexagonal boron nitride nanosheets (BNNSs) is reported. This observation was attributed to the long range crystallinity and the contaminant-free surfaces of these chemically inert nanosheets. Parallel-line-like Moiré fringes with similarly large periodicities were also observed. The simulations and experiments unambiguously revealed that the hexagonal patterns and the parallel fringes originated from the same rotationally mismatched vdW stacking of BNNSs and can be inter-converted by simply tilting the TEM specimen following designated directions. This finding may pave the way for further structural decoding of other 2D vdW superstructure systems with more complex Moiré images.
authors.affiliation: National Institute of Aerospace, 100 Exploration Way, Hampton, VA, 23666, USA.|Department of Chemistry, Institute for Functional Nanomaterials, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico, 00931, USA.
authors.forename: Yunlong
authors.initials: Y
authors.lastname: Liao
authors.affiliation: Applied Research Center, Old Dominion University, 12050 Jefferson Avenue, Newport News, VA 23606, USA.
authors.forename: Wei
authors.initials: W
authors.lastname: Cao
authors.affiliation: Advanced Materials and Processing Branch, NASA Langley Research Center, Hampton, VA, 23681-2199, USA.
authors.forename: John W
authors.initials: JW
authors.lastname: Connell
authors.affiliation: Department of Chemistry, Institute for Functional Nanomaterials, University of Puerto Rico, Rio Piedras Campus, San Juan, Puerto Rico, 00931, USA.
authors.forename: Zhongfang
authors.initials: Z
authors.lastname: Chen
authors.affiliation: National Institute of Aerospace, 100 Exploration Way, Hampton, VA, 23666, USA.|Department of Applied Science, The College of William and Mary, Williamsburg, VA, 23185, USA.
authors.forename: Yi
authors.initials: Y
authors.lastname: Lin