Energy-resolved Photoconductivity Mapping in a Monolayer-bilayer WSe2 Lateral Heterostructure

Abstract

Vertical and lateral heterostructures of van der Waals materials provide tremendous flexibility for band structure engineering. Since electronic bands are sensitively affected by defects, strain, and interlayer coupling, the edge and heterojunction of these two-dimensional (2D) systems may exhibit novel physical properties, which can be fully revealed only by spatially resolved probes. Here, we report the spatial mapping of photoconductivity in a monolayer-bilayer WSe2 lateral heterostructure under multiple excitation lasers. As the photon energy increases, the light-induced conductivity detected by microwave impedance microscopy first appears along the hetero-interface and bilayer edge, then along the monolayer edge, inside the bilayer area, and finally in the interior of the monolayer region. The sequential emergence of mobile carriers in different sections of the sample is consistent with the theoretical calculation of local energy gaps. Quantitative analysis of the microscopy and transport data also reveals the linear dependence of photoconductivity on the laser intensity and the influence of interlayer coupling on carrier recombination. Combining theoretical modeling, atomic scale imaging, mesoscale impedance microscopy, and device-level characterization, our work suggests an exciting perspective to control the intrinsic band-gap variation in 2D heterostructures down to the few-nanometer regime.

arXiv comment18 pages, 5 figures; Nano Lett., Just Accepted Manuscript

References in corpus (23)

• Atomically thin MoS2: A new direct-gap semiconductor
• Van der Waals heterostructures
• 2D materials and van der Waals heterostructures
• Two-Dimensional Material Nanophotonics
• Evolution of Electronic Structure in Atomically Thin Sheets of WS2 and WSe2
• Quantum Spin Hall Effect and Topological Field Effect Transistor in Two-Dimensional Transition Metal Dichalcogenides
• Solar-energy conversion and light emission in an atomic monolayer p-n diode
• Strong interlayer coupling in van der Waals heterostructures built from single-layer chalcogenides
• Electroluminescence and photocurrent generation from atomically sharp WSe2/MoS2 heterojunction p-n diodes
• Three-band tight-binding model for monolayers of group-VIB transition metal dichalcogenides
• Observation of the Quantum Spin Hall Effect up to 100 Kelvin in a Monolayer Crystal
• Evolution of Interlayer Coupling in Twisted MoS2 Bilayers
• Mechanisms of photoconductivity in atomically thin MoS2
• Edge conduction in monolayer WTe2
• Photoconductivity of biased graphene
• Direct imaging of the band profile in single layer $Mo{S}_2$ on graphite: quasiparticle energy gap, metallic edge states and edge band bending
• Impact of Grain Boundaries on Efficiency and Stability of Organic-Inorganic Trihalide Perovskites
• Topological mosaic in Moiré superlattices of van der Waals heterobilayers
• Elucidating the photoresponse of ultrathin MoS2 field-effect transistors by scanning photocurrent microscopy
• Visualizing Band Offsets and Edge States in Bilayer-Monolayer Transition Metal Dichalcogenides Lateral Heterojunction
• Modeling of a Cantilever-Based Near-Field Scanning Microwave Microscope
• Uncovering edge states and electrical inhomogeneity in MoS2 field-effect transistors
• Tailoring Semiconductor Lateral Multi-junctions for Giant Photoconductivity Enhancement

Cited by in corpus (3)

• Unveiling Defect-Mediated Carrier Dynamics in Monolayer Semiconductors by Spatiotemporal Microwave Imaging
• Superior Photo-carrier Diffusion Dynamics in Organic-inorganic Hybrid Perovskites Revealed by Spatiotemporal Conductivity Imaging
• Spatially Resolved Persistent Photoconductivity in MoS${}_2$-WS${}_2$ Lateral Heterostructures