Polymorphic In-Plane Heterostructures of Monolayer WS₂ for Light-Triggered Field-Effect Transistors

Abstract

The realization of next-generation transition-metal dichalcogenide based nanoscale devices demands stringent control over coherent in-plane heterostructures of atomically thin monolayers with exceptional properties. In this paper, we report atmospheric-pressure chemical vapor deposition growth of largedomain, coherent polymorphic in-plane heterostructures of monolayer WS 2 on a SiO 2 /Si substrate with intriguing optical and electronic properties. The formation of in-plane heterostructures with 1H and 1T polymorphs was extensively analyzed using a variety of spectroscopic as well as microscopic techniques, along with lifetime luminescence imaging. High-angle annular dark-field scanning transmission electron microscopy revealed coexistence of the heterophases in monolayer WS 2 heterostructures. Back-gated photoconductivity measurements in nanoscale field-effect-transistor device geometry and the rational design of a WS 2 heterostructure pattern demonstrate optoelectronic applications.

Monolayer WS2 Lateral Homosuperlattices with Two-dimensional Periodic Localized Photoluminescence

“…In addition, the uniform height profile in the green line further reveals the formation of seamless 2D MLHSs. ,,, Along the white dashed triangle, we observe that there is an obvious contact potential difference ( V CPD ) or work function difference between the 1T and 2H phases in the corresponding Kelvin probe force microscopy (KPFM) image (Figure b). The surface potential of the 1T region is higher, and the surface potential difference is approximately 48 mV across the interface of the 1T and 2H domains, which is in congruence with the V CPD reported in other literature. ,, Hence, charge transfer might occur from 1T regions to 2H regions, suggesting electronic doping. More electrons in the 2H regions are localized in the potential well formed by the MLHS structure with 1T/2H-WS 2 .…”

“…Neutral excitons and negative trions are often exploited to understand the fundamental behavior behind the PL emission in layered WS 2 materials. The behaviors of excitons generally dominate the optical properties and light emission of 2D semiconductor materials. ,,, Figure a outlines the schematic illustration of the neutral exciton and negative trion in the WS 2 monolayer. The atomic layer thickness causes a strong Columbic interaction between electrons and holes in the WS 2 monolayer. , Both neutral excitons and charged excitons exist with a high exciton density in monolayer WS 2.…”

Dendritic WS2 Nanocrystal-Coated Monolayer WS2 Nanosheet Heterostructures for Phototransistors

“…In Figure 2d, there is an obvious contact potential difference (V CPD ) on the surface of the isomeric structures, which means the nature of 2D material Fermi surfaces determines the work function corresponding to the surface potential. 32 The transmission electron microscopy (TEM) was used to illustrate the crystal structure, Figure S4b shows a 2000 mesh copper grid (2000, 7.5 um, England) was used to deposit the dendritic WS 2 /monolayer WS 2 flake. The low-magnified high-resolution TEM (HRTEM) image from dendritic WS 2 /monolayer WS 2 domain edge is shown in Figure 2e, indicating that dendritic structures are stacked at the boundary of the monolayer WS 2 .…”

“…In addition, Kelvin probe force microscopy (KPFM) was used to measure the intrinsic surface potential of the heterostructure of the triangular domain (Figure S4a). In Figure d, there is an obvious contact potential difference (V CPD ) on the surface of the isomeric structures, which means the nature of 2D material Fermi surfaces determines the work function corresponding to the surface potential . The transmission electron microscopy (TEM) was used to illustrate the crystal structure, Figure S4b shows a 2000 mesh copper grid (2000, 7.5 um, England) was used to deposit the dendritic WS 2 /monolayer WS 2 flake.…”

Efficacy of boron nitride encapsulation against plasma-processing of 2D semiconductor layers

“…Plasma processing is widely used to clean, functionalize and passivate surfaces, as well as to etch materials. [5][6][7][8][9][10][11] It has been applied to 2D materials since the early days of graphene device research. [12][13][14][15] However, it was soon realized that energetic plasmas could affect the structural and chemical stability of 2D materials and thereby degrade lateral transport in electronic devices.…”