A dielectric-defined lateral heterojunction in a monolayer semiconductor

Abstract

Due to their low dimensionality, two-dimensional semiconductors, such as monolayer molybdenum disulfide, have a range of properties that make them valuable in the development of nanoelectronics. For example, the electronic bandgap of these semiconductors is not an intrinsic physical parameter and can be engineered through the dielectric environment around the monolayer. Here we show that this dielectric dependent electronic bandgap can be used to engineer a lateral heterojunction within a homogeneous MoS 2 monolayer. We visualize the heterostructure with Kelvin probe force microscopy and examine its influence on electrical transport experimentally and theoretically. We observe a lateral heterojunction with ~90 meV band offset due to different bandgap renormalization of monolayer MoS 2 when it is on a substrate in which one segment is made from an amorphous fluoropolymer (Cytop) and another segment from hexagonal boron nitride. This heterostructure leads to a diode-like electrical transport with a strong asymmetric behaviour.

Rigid Band Shifts in Two-Dimensional Semiconductors through External Dielectric Screening

“…By embedding atomically-thin materials in different dielectric environments, their band gaps, as well as exciton binding energies, can therefore be modified on an energy scale of the exciton binding energies themselves [8][9][10]. This sensitivity becomes particularly important in vertical heterostructures of 2D materials and enables a non-invasive way of designing nanoscale functionality, such as lateral heterojunctions, through the spatial control of substrate dielectrics [8,10,11].To exploit the full potential of tailoring Coulomb interactions through control of the dielectric environment, it is critical to understand its impact not only on the band gap but also on the valence and conduction band dispersions. The dispersion determines such basic properties as the effective masses of the carriers and the energy differences between different valleys within the Brillouin zone, and also affects the relative alignment between the valence and conduction bands of a homogeneous monolayer with spatially varying external dielectric screening.…”

“…By embedding atomically-thin materials in different dielectric environments, their band gaps, as well as exciton binding energies, can therefore be modified on an energy scale of the exciton binding energies themselves [8][9][10]. This sensitivity becomes particularly important in vertical heterostructures of 2D materials and enables a non-invasive way of designing nanoscale functionality, such as lateral heterojunctions, through the spatial control of substrate dielectrics [8,10,11].…”

Anisotropic circular photogalvanic effect in colloidal tin sulfide nanosheets

“…Since the dielectric constant of the substrate significantly differs from vacuum, distinct screening patterns are formed on different sides of the nanosheets, which modifies the band structure and breaks the inversion symmetry. 21,22,24,28,29 As a result, the symmetry of the crystal is reduced to a C 2v one, which supports the generation of the CPGE. 19,21 Other factors like defects or temperature gradient effects could also enhance the asymmetry of the crystal.…”

2D Materials Nanoelectronics: New Concepts, Fabrication, Characterization From Microwaves up to Optical Spectrum

“…This effect is named dielectric‐induced bandgap renormalization and this effect is opening a new way of bandgap engineering. Very recently, this concept was experimentally tested via a lateral heterotructure based on two dielectrics: cytop, having , and hBN, with , which induce a type I heterostructure with a bandgap offset of 90 meV.…”