Direct imaging and electronic structure modulation of moiré superlattices at the 2D/3D interface

Abstract

The atomic structure at the interface between two-dimensional (2D) and three-dimensional (3D) materials influences properties such as contact resistance, photo-response, and high-frequency electrical performance. Moiré engineering is yet to be utilized for tailoring this 2D/3D interface, despite its success in enabling correlated physics at 2D/2D interfaces. Using epitaxially aligned MoS2/Au{111} as a model system, we demonstrate the use of advanced scanning transmission electron microscopy (STEM) combined with a geometric convolution technique in imaging the crystallographic 32 Å moiré pattern at the 2D/3D interface. This moiré period is often hidden in conventional electron microscopy, where the Au structure is seen in projection. We show, via ab initio electronic structure calculations, that charge density is modulated according to the moiré period, illustrating the potential for (opto-)electronic moiré engineering at the 2D/3D interface. Our work presents a general pathway to directly image periodic modulation at interfaces using this combination of emerging microscopy techniques.

Defect-mediated ripening of core-shell nanostructures

“…Here, with cadmium-cadmium chloride (Cd-CdCl 2 ) CSN as a model system, we study the ripening of colloidal nanocrystals with a focus on the role of defects. We track the structural evolution of Cd-CdCl 2 core-shell nanoparticles by taking advantage of the recent advances in liquid cell transmission electron microscopy (LC-TEM) 18 – 21 . With thin carbon films as the liquid cell membrane, atomic resolution imaging is achieved, which provides opportunities to reveal defect-mediated ripening of Cd-CdCl 2 core-shell nanocrystals.…”

Atomic-scale characterization of structural heterogeny in 2D TMD layers

“…For instance, it is anticipated that advanced TEM techniques will play an essential role Page 28 of 36 in the fabrication and characterization of recently discovered 2D bilayer superlattice with specific angles (also known as super angles). [91][92][93] The vertical stacks of two 2D layers forming bilayer with a twist angle results in the formation of superlattice, exhibiting extraordinary electrical and optical properties. The superlattice-induced special features (e.g., superconductivity, moiré excitons, and interlayer decoupling) have been attributed to the interlayer electronic coupling enhanced by surface-exposed electronic states as well as quantum confinement.…”

“…For instance, it is anticipated that advanced TEM techniques will play an essential role in the fabrication and characterization of recently discovered 2D bilayer superlattices with specific angles (also known as super angles). 91–93 The vertical stacks of two 2D layers forming bilayer with a twist angle results in the formation of a superlattice, exhibiting extraordinary electrical and optical properties. The superlattice-induced special features ( e.g.…”

Moiré patterns generated by stacked 2D lattices: a general algorithm to identify primitive coincidence cells

“…A moiré superstructure can be defined as the interference figure due to the overlap of two or more patterns [1]. Such structures can be commonly observed in surface science when, for example, a layer of a material is supported on a substrate having a different lattice periodicity [2][3][4][5][6]. The issue of stacking different lattices is involved also in the formation of novel materials through layer-by-layer combinations of 2D systems [7][8][9], a field nowadays in rapid expansion after the discovery of graphene [10].…”