Strain, doping and electronic transport of large area monolayer MoS2 exfoliated on gold and transferred to an insulating substrate

Abstract

Gold-assisted mechanical exfoliation currently represents a promising method to separate ultra-large (cm-scale) transition metal dichalcogenides (TMDs) monolayers (1L) with excellent electronic and optical properties from the parent van der Waals (vdW) crystals. The strong interaction between $Au$ and chalcogen atoms is the key to achieve this nearly perfect 1L exfoliation yield. On the other hand, it may affect significantly the doping and strain of 1L TMDs in contact with Au. In this paper, we systematically investigated the morphology, strain, doping, and electrical properties of large area 1L $Mo{S}_2$ exfoliated on ultra-flat $Au$ films ($0.16-0.21nm$ roughness) and finally transferred to an insulating $A{l}_2{O}_3$ substrate. Raman mapping and correlative analysis of the $E^{\prime }$ and $A{1}^{\prime }$ peaks positions revealed a moderate tensile strain ($0.2\%$) and p-type doping ($n=-0.25\times 10^{13}c{m}^{-2}$) of 1L $Mo{S}_2$ in contact with $Au$. Nanoscale resolution current mapping and current-voltage (I-V) measurements by conductive atomic force microscopy (C-AFM) showed direct tunnelling across the 1L $Mo{S}_2$ on $Au$, with a broad distribution of tunnelling barrier values (from 0.7 to 1.7 eV) consistent with the p-type doping of $Mo{S}_2$. After the final transfer of $1L-Mo{S}_2$ on $A{l}_2{O}_3/Si$, the strain was converted to compressive ($-0.25\%$). Furthermore, an n-type doping ($n=0.5\times 10^{13}c{m}^{-2}$) was deduced by Raman mapping and confirmed by electrical measurements of an $A{l}_2{O}_3/Si$ back-gated 1L $Mo{S}_2$ transistor. These results provide a deeper understanding of the $Au$-assisted exfoliation mechanisms and can contribute to its widespread applications for the realization of novel devices and artificial vdW heterostructures

References in corpus (10)

• Two Dimensional Atomic Crystals
• Anomalous Lattice Vibrations of Single and Few-Layer MoS2
• Synthesis of Large-Area MoS2 Atomic Layers with Chemical Vapor Deposition
• Uniaxial Strain in Graphene by Raman Spectroscopy: G peak splitting, Gruneisen Parameters and Sample Orientation
• Symmetry-dependent phonon renormalization in monolayer MoS2 transistor
• Optical Separation of Mechanical Strain from Charge Doping in Graphene
• Epitaxial graphene
• Band Gap Engineering with Ultralarge Biaxial Strains in Suspended Monolayer MoS2
• Spectroscopic Evaluation of Charge-transfer Doping and Strain in Graphene/MoS2 Heterostructures
• Aluminum oxide nucleation in the early stages of atomic layer deposition on epitaxial graphene

Cited by in corpus (7)

• Substrate impact on the thickness dependence of vibrational and optical properties of large area $Mo{S}_2$ produced by gold-assisted exfoliation
• Direct atomic layer deposition of ultra-thin $A{l}_2{O}_3$ and $Hf{O}_2$ films on gold-supported monolayer $Mo{S}_2$
• Atomic resolution interface structure and vertical current injection in highly uniform $Mo{S}_2$ heterojunctions with bulk GaN
• Dielectric screening at TMD:hBN interfaces: Monolayer-to-bulk transition, local-field effect, and spatial dependence
• Nano-optical investigation of grain boundaries, strain and edges in CVD grown MoS${}_2$ monolayers
• Curvature-enhanced localised emission from dark states in wrinkled monolayer WSe2 at room temperature
• Tracking the photoinduced dynamics of a dark excitonic state in single-layer WS${}_2$ via resonant Autler-Townes splitting