title: Unraveling the 3D Atomic Structure of a Suspended Graphene/hBN van der Waals Heterostructure.
abstract: In this work we demonstrate that a free-standing van der Waals heterostructure, usually regarded as a flat object, can exhibit an intrinsic buckled atomic structure resulting from the interaction between two layers with a small lattice mismatch. We studied a freely suspended membrane of well-aligned graphene on a hexagonal boron nitride (hBN) monolayer by transmission electron microscopy (TEM) and scanning TEM (STEM). We developed a detection method in the STEM that is capable of recording the direction of the scattered electron beam and that is extremely sensitive to the local stacking of atoms. A comparison between experimental data and simulated models shows that the heterostructure effectively bends in the out-of-plane direction, producing an undulated structure having a periodicity that matches the moiré wavelength. We attribute this rippling to the interlayer interaction and also show how this affects the intralayer strain in each layer.
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Giacomo
authors.identifier: 0000-0003-0406-8208
authors.initials: G
authors.lastname: Argentero
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Mittelberger
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Reza Ahmadpour Monazam
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Pennycook
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Clemens
authors.initials: C
authors.lastname: Mangler
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Kramberger
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Jani
authors.identifier: 0000-0002-1301-5266
authors.initials: J
authors.lastname: Kotakoski
authors.forename: A K
authors.initials: AK
authors.lastname: Geim
authors.affiliation: Faculty of Physics, University of Vienna , Boltzmanngasse 5, 1090 Vienna, Austria.
authors.forename: Jannik C
authors.identifier: 0000-0003-4023-0778
authors.initials: JC
authors.lastname: Meyer
keywords: graphene; hexagonal boron nitride; scanning transmission electron microscopy; van der Waals heterostructures