MoirŽ Engineering in 2D Materials Beyond Graphene
Abstract
Layered 2D materials beyond graphene offer a tremendous space for engineering design, both as a platform for emergent physics and novel devices. Within this space, we propose to Introduce a new field of Moire Engineering, or the intentional design of Moire patterns in beyond-graphene 2D materials. Moire patterns are periodic electronic structure objects caused by the Van der Waals interactions that occur naturally in the stacking of 2D materials. Moire Engineering refers to the design of defects in the Moire, which are topologically protected states, with novel electronic properties over large areas. This high-risk, high-payoff concept has the potential to open a new technological space: a class of electronic and optoelectronic devices based on engineered Moire patterns. The concept of Moire Engineering is based on the arrangement of interlayer or Van der Waals (VdW) dislocations as the building block of Moire patterns in 2D layered structures. The presence of VdW dislocations is due to crystallographic incommensurability caused by twist or extensional misfit strain. The resulting periodic structures may be characterized by Burgers vectors and line directions. This concept applies to all 2D materials that interact through VdW bonding, including h-BN, transition metal dichalcogenides (TMDs), phosphorcne, silicene, etc., stacked on one another or on crystalline metal support layers. A Moire pattern is simply a VdW dislocation array. The same structures are sometimes referred to as solitons or commensurability/ incommensurability domain boundaries. Moire patterns, as periodic structures, may themselves contain point, line, and planar defects. These defects are topologically protected states, the result of broken symmetry in the commensurability relationship between any two layers of stacked 2D materials. In this project we will show that the power of Moire engineering lies in our ability to predict, control, and reconfigure the nature and presence of these electronic structure signatures. Through appropriate selection of the constituent materials and underlying defects, Moire engineering makes it possible to achieve device structures with states that may permit mechanisms enabling extreme high electron mobility, or novel optical absorption. We will determine general principles of Moire design, as well as specific Moire structures that may be achieved through design of defects in the covalent lattices, combined with application of stretching and compressive strains as well as rigid body rotations between 2D layers. In preliminary work we have shown that our computational approach can capture the Moire, which reveals possible charge density waves seen experimentally in MoSe2/graphene due to the presence of an anti-phase boundary in the MoSe2. We also predict, for example, that a similar but stronger Moire signature exists in h-BN on Ru due to a different anti-phase boundary in h-BN. The project will cover theoretical work only, and will support one graduate student. The work will be directed by the PI (Johnson) at UlUC, and will involve a collaboration with a researcher (Pochet) in CEA-Grenoble, France.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 16, 2018
- Source ID
- W911NF1710544
Entities
People
- Harley Johnson
Organizations
- Army Contracting Command
- United States Army
- University of Illinois Urbana–Champaign