Nanoscale mapping of quasiparticle band alignment

Søren Ulstrup,Olga Kazakova,Mauricio Terrones,Pavel Dudin,Cristina E Giusca,D Kurt Gaskill,Philip Hofmann,Cephise Cacho,Tianyi Zhang,Rachael L Myers-Ward,Charlotte E Sanders,Alex Browning,Jill A Miwa

doi:10.1038/s41467-019-11253-2

Abstract

Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices. In the case of two-dimensional materials, disparate electronic structures can be realized even within a single uniform sheet, merely by locally applying different vertical gate voltages. Here, we utilize the inherently nano-structured single layer and bilayer graphene on silicon carbide to investigate lateral electronic structure variations in an adjacent single layer of tungsten disulfide (WS2). The electronic band alignments are mapped in energy and momentum space using angle-resolved photoemission with a spatial resolution on the order of 500 nm (nanoARPES). We find that the WS2 band offsets track the work function of the underlying single layer and bilayer graphene, and we relate such changes to observed lateral patterns of exciton and trion luminescence from WS2.

Highlights

Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices
We investigate the interplay of quasiparticle band alignments and optical properties in a lateral heterostructure of semiconducting single layer (SL) WS2 placed on alternating areas of SL graphene (SLG) and bilayer graphene (BLG) grown on SiC
This groundbreaking technique for electronic structure characterization provides three key new insights for the type of van der Waals heterostructure investigated here, which could not be accessed in conventional ARPES measurements that merely reveal the laterally averaged electronic structure: (i) We can determine the energy- and momentum-dependence of band alignments at truly 2D interfaces, (ii) we obtain detailed spatially resolved information on how the electronic structure of a 2D semiconductor is modified around the one-dimensional (1D) SLG/BLG interface, and (iii) we can spatially disentangle the electronic dispersions of SL WS2 and few-layer (FL) WS2, and distinguish between islands of different orientations

Summary

Introduction

Control of atomic-scale interfaces between materials with distinct electronic structures is crucial for the design and fabrication of most electronic devices. This groundbreaking technique for electronic structure characterization provides three key new insights for the type of van der Waals heterostructure investigated here, which could not be accessed in conventional ARPES measurements that merely reveal the laterally averaged electronic structure (for example, in TMDs synthesized on metal substrates[23,24] or graphene/SiC substrates25–27): (i) We can determine the energy- and momentum-dependence of band alignments at truly 2D interfaces, (ii) we obtain detailed spatially resolved information on how the electronic structure of a 2D semiconductor is modified around the one-dimensional (1D) SLG/BLG interface, and (iii) we can spatially disentangle the electronic dispersions of SL WS2 and few-layer (FL) WS2, and distinguish between islands of different orientations

Methods

Results

Conclusion