One-dimensional bandgap modulation at continuous few-layer MoS2 steps

In pursuit of novel two-dimensional devices, lateral heterostructures based on transition metal dichalcogenides (TMDCs) have been intensively proposed and demonstrated. For instance, heterojunctions composed of TMDCs with different thicknesses function attractively in electronics and optoelectronics. Using scanning tunneling microscopy and spectroscopy, we resolved electronic structures of three types of few-layer MoS2 steps: flake edges, continuous bilayer–monolayer steps, and monolayers sitting on highly oriented pyrolytic graphite steps. Each type possesses unique bandgap features, including in-gap states and npn-like band alignment, which suggests modifiable 1D bandgaps via choices of edge conditions for the development of lateral TMDC devices.