Nanospot angle-resolved photoemission study of Bernal-stacked bilayer graphene on hexagonal boron nitride: Band structure and local variation of lattice alignment

Abstract

Heterostructures composed of two-dimensional (2D) materials placed on insulating substrates are of great interest because they exhibit tunable electronic and optical properties that enable novel optoelectronic devices. Directly accessing the electronic band structure of such heterostructures is challenging because of their micron-scale size. The recent development of nanospot angle-resolved photoemission spectroscopy (nanoARPES) now provides direct access to the band structure with high resolution in space, energy, and momentum. To this end, the authors use nanoARPES to reveal the electronic structure of Bernal-stacked bilayer graphene (BLG) supported by hexagonal boron nitride (hBN). They extract tight-binding band parameters for BLG on this substrate for the first time, thus providing important information for theoretical modeling. With the help of STM, they also find spatial inhomogeneity in the lattice alignment between the supporting hBN and the top-lying BLG. Considering the dramatic influence that the alignment angle has on the properties of 2D material heterostructures, this surprisingly large inhomogeneity (up to 3) must be considered for interpreting previous and future spatially averaged experiments performed on these heterostructures.