Enhancing and quantifying spatial homogeneity in monolayer WS2

Cao, Yameng; Wood, Sebastian; Richheimer, Filipe; Blakesley, James C.; Young, Robert J.; Castro, Fernando A.

doi:10.1038/s41598-021-94263-9

Cited by 12 publications

(8 citation statements)

References 66 publications

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“…We start our considerations by the PL measurements, which were accomplished with the same experimental conditions for all the samples. We are cautious with the laser exposure and spectra acquisition to minimize changes in the PL caused by photodoping effects 22 and to allow the comparison of PL spectra from different samples. (Details are provided in the supplementary material.)…”

mentioning

confidence: 99%

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Rojas-Lopez

Brant

Ramos

et al. 2021

Applied Physics Letters

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The new generation of two-dimensional (2D) materials has shown a broad range of applications for optical and electronic devices. Understanding the properties of these materials when integrated with more traditional three-dimensional (3D) semiconductors is an important challenge for the implementation of ultra-thin electronic devices. Recent observations have shown that by combining MoS 2 with GaAs, it is possible to develop high quality photodetectors and solar cells. Here, we present a study of effects of intrinsic GaAs, p-doped GaAs, and n-doped GaAs substrates on the photoluminescence of monolayer MoS 2 . We observe a decrease in an order of magnitude in the emission intensity of MoS 2 in all MoS 2 /GaAs heterojunctions, when compared to a control sample consisting of a MoS 2 monolayer isolated from GaAs by a few layers of hexagonal boron nitride. We also see a dependence of the trion to A-exciton emission ratio in the photoluminescence spectra on the type of substrates, a dependence that we relate to the static charge exchange between MoS 2 and the substrates when the junction is formed. Scanning Kelvin probe microscopy measurements of heterojunctions suggest type-I band alignments, so that excitons generated on the MoS 2 monolayer will be transferred to the GaAs substrate. Our results shed light on the charge exchange leading to band offsets in 2D/3D heterojunctions, which play a central role in the understanding and further improvement of electronic devices.

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confidence: 99%

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Rojas-Lopez

Brant

Ramos

et al. 2021

Applied Physics Letters

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“…Then the laser beam is focused onto the fiber by an oil-immersion objective (60×, NA = 1.42, UPLXAPO60XO, OLYMPUS, Shinjuku City, Japan). The diameter of the focused beam spot is 447 nm according to the diffraction limit D = 1.22λ/NA [ 31 ]. LED illumination and CCD real-time monitoring system are integrated into this system to facilitate the FBG inscription.…”

Section: Experimental Set-upmentioning

confidence: 99%

Direct Bragg Grating Inscription in Single Mode Step-Index TOPAS/ZEONEX Polymer Optical Fiber Using 520 nm Femtosecond Pulses

Chen

Gao

et al. 2022

Polymers

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We experimentally report fiber Bragg gratings (FBGs) in a single mode step-index polymer optical fiber (POF) with a core made of TOPAS and cladding made of ZEONEX using 520 nm femtosecond pulses and a point-by-point (PbP) inscription method. With different pulse energies between 69.8 nJ and 80.4 nJ, 12 FBGs are distributed along the cores of two pieces of POFs with negative averaged effective index change up to ~6 × 10−4 in the TOPAS. For POF 1 with FBGs 1–6, the highest reflectivity 45.1% is obtained with a pulse energy of 76.1 nJ. After inscription, good grating stability is reported. Thanks to the post-annealing at 125 °C for 24 h, after cooling the grating reflectivity increases by ~10%. For POF 2 with FBGs 7–12, similar FBG data are obtained showing good reproducibility. Then, the FBGs are annealed at 125 °C for 78 h, and the average reflectivity of the FBGs during the annealing process increases by ~50% compared to that before the annealing, which could be potentially applied to humidity insensitive high temperature measurement.

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“…The spatial uniformity in the VdWE WS 2 /MoS 2 heterostructures are investigated by PL mapping. A recent report 39 has shown that the PL uniformity in exfoliated 2D materials is strongly correlated to the uniformity in the spectral properties, such as the emission energy and spectral weighting. A similar analysis is applied here to investigate the uniformity of the heterostructures, in terms of the emission energies of each of the corresponding layers in the heterostructure and offer a baseline for comparisons with future studies.…”

Section: Resultsmentioning

confidence: 99%

Facilitating Uniform Large-Scale MoS₂, WS₂ Monolayers, and Their Heterostructures through van der Waals Epitaxy

Huang

Wang

Cao

et al. 2022

ACS Appl. Mater. Interfaces

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The fabrication process for the uniform large-scale MoS2, WS2 transition-metal dichalcogenides (TMDCs) monolayers, and their heterostructures has been developed by van der Waals epitaxy (VdWE) through the reaction of MoCl5 or WCl6 precursors and the reactive gas H2S to form MoS2 or WS2 monolayers, respectively. The heterostructures of MoS2/WS2 or WS2/MoS2 can be easily achieved by changing the precursor from WCl6 to MoCl5 once the WS2 monolayer has been fabricated or switching the precursor from MoCl5 to WCl6 after the MoS2 monolayer has been deposited on the substrate. These VdWE-grown MoS2, WS2 monolayers, and their heterostructures have been successfully deposited on Si wafers with 300 nm SiO2 coating (300 nm SiO2/Si), quartz glass, fused silica, and sapphire substrates using the protocol that we have developed. We have characterized these TMDCs materials with a range of tools/techniques including scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), micro-Raman analysis, photoluminescence (PL), atomic force microscopy (AFM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and selected-area electron diffraction (SAED). The band alignment and large-scale uniformity of MoS2/WS2 heterostructures have also been evaluated with PL spectroscopy. This process and resulting large-scale MoS2, WS2 monolayers, and their heterostructures have demonstrated promising solutions for the applications in next-generation nanoelectronics, nanophotonics, and quantum technology.

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Enhancing and quantifying spatial homogeneity in monolayer WS2

Cited by 12 publications

References 66 publications

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Direct Bragg Grating Inscription in Single Mode Step-Index TOPAS/ZEONEX Polymer Optical Fiber Using 520 nm Femtosecond Pulses

Facilitating Uniform Large-Scale MoS₂, WS₂ Monolayers, and Their Heterostructures through van der Waals Epitaxy

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Enhancing and quantifying spatial homogeneity in monolayer WS2

Cited by 12 publications

References 66 publications

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Photoluminescence and charge transfer in the prototypical 2D/3D semiconductor heterostructure MoS2/GaAs

Direct Bragg Grating Inscription in Single Mode Step-Index TOPAS/ZEONEX Polymer Optical Fiber Using 520 nm Femtosecond Pulses

Facilitating Uniform Large-Scale MoS2, WS2 Monolayers, and Their Heterostructures through van der Waals Epitaxy

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Facilitating Uniform Large-Scale MoS₂, WS₂ Monolayers, and Their Heterostructures through van der Waals Epitaxy