Inter-layer Interactions as a Function of Mismatch Angle in 2-D Systems

Nathan Finney, Columbia University

Mechanical and electronic properties of layered heterostructures are highly dependent on the relative crystallographic orientation between the layers. The goal of this work is to probe changes in the vibrational modes and electronic band structure using Raman spectroscopy and Photoluminescence spectroscopy while varying a new experimental degree of freedom: angular orientation between layers. We achieve angular control between two atomically flat layered materials by physically pushing the uppermost section of the heterostructure with an atomic force microscope (AFM) in contact mode. We study two types of phenomena: induced strain in a monolayer by angular alignment with an atomically flat substrate; and charge transfer between a layered transition metal dichalcogenide (TMD) and an atomically flat graphitic substrate. Our preliminary results for the strain study show a change in spectrum related to variation in strain. In the charge transfer studies we show a promising variation in the intensity of the photoluminescence, indicating a possible angle-dependent charge transfer between TMD and graphite.

Abstract Author(s): Nathan Finney, Rebeca Ribiero-Palau, Xiaoxiao Zhang, Kursti DeLello, Daniel Rhodes, Tony Heinz, Cory Dean, James Hone