Local Electronic Properties of Coherent Single-Layer WS₂/WSe₂ Lateral Heterostructures

Abstract

Lateral single-layer transition metal dichalcogenide (TMD) heterostructures are promising building blocks for future ultrathin devices. Recent advances in the growth of coherent heterostructures have improved the structural precision of lateral heterojunctions, but an understanding of the electronic effects of the chemical transition at the interface and associated strain is lacking. Here we present a scanning tunneling microscopy study of single-layer coherent TMD heterostructures with nearly uniform strain on each side of the heterojunction interface. We have characterized the local topography and electronic structure of single-layer WS2/WSe2 heterojunctions exhibiting ultrasharp coherent interfaces. Uniform built-in strain on each side of the interface arising from lattice mismatch results in a reduction of the bandgap of WS2. By mapping the tunneling differential conductance across the interface, we find type-II band alignment and an ultranarrow electronic transition region only ∼3 nm in width that arises from wave function mixing between the two materials.

Interface engineering of charge-transfer excitons in 2D lateral heterostructures

“…Figure 1 b schematically shows the spatial variation of single-particle energies in the considered lateral heterostructure. The conduction and valence bands form offsets Δ E c , Δ E v at the interface, typically inducing a type II alignment 12 , 20 , 22 – 24 with the conduction band minimum located in the MoSe 2 layer 18 . Note that for gate-induced homojunctions 25 – 27 , the band offsets are the same, i.e.…”

“…The junction width w depends on the exact growth technique and conditions. Recently, there has been an impressive technological development in lateral heterostructures allowing the realization of atomically narrow junctions of just a few nanometers 13 , 14 , 20 , 23 , 24 , 33 , 34 . In Fig.…”

Coherent Heterostructure Mesh Grown by Gap-Filling Epitaxial Chemical Vapor Deposition

“…Metal organic chemical vapor deposition (MOCVD) was adopted to synthesize coherent tungsten disulfide (WS 2 ) and tungsten diselenide (WSe 2 ) heterostructure despite large lattice mismatch (∼4%), which provides a platform for research on strain-induced electronic state transition. 12 Chemical vapor deposition (CVD) has also enabled the one-pot growth of MoS 2 /MoSe 2 , 13 WS 2 /WSe 2 , 13 WSe 2 /MoSe 2 , 14 and WS 2 /MoS 2 15 heterostructures or the sequent growth of the WSe 2 /MoS 2 heterostructure. 9 Efforts have also been devoted to achieve spatial control of the second material by combining CVD with other techniques.…”

Creating a Nanoscale Lateral Junction in a Semiconductor Monolayer with a Large Built-in Potential

“…However, future technology based on TMDs hinges on the capability of creating nanoscale lateral junctions with large built-in potentials. Following the paradigm of three-dimensional counterparts, lateral heterojunctions have been directly synthesized by laterally stitching two different TMD monolayers together, − although the built-in potentials are on the order of hundreds of meV, limited by the TMD library . Development of substitutional doping is challenging to spatially control while avoiding degradation due to the atomic thin nature of TMDs.…”