Spatial Control of Substitutional Dopants in Hexagonal Monolayer WS<sub>2</sub>: The Effect of Edge Termination

Zhang, Tianyi; Liu, Mingzu; Fujisawa, Kazunori; Lucking, Michael; Beach, Kory; Zhang, Fu; Shanmugasundaram, Maruda; Krayev, Andrey; Murray, William T.; Lei, Yu; Yu, Zhuohang; Sanchez, David Emanuel; Liu, Zhiwen; Terrones, Humberto; Elías, Ana Laura; Terrones, Mauricio

doi:10.1002/smll.202205800

Cited by 17 publications

(14 citation statements)

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“…The difference in chemical potential of the S‐zigzag and W‐zigzag boundary is used to explain the spatial distribution inhomogeneity in hexagonal WS 2 . [ 29 ] However, triangular WS 2 domains have uniform edge structures, so the mechanism could not be used to explain the CPS phenomenon in our experiment.…”

Section: Resultsmentioning

confidence: 95%

“…Zhang et al controlled the spatial distribution of dopants by utilizing the different chemical potentials of the W-zigzag and S-zigzag edges of hexagonal WS 2 . [29] Nevertheless, the synthesis of hexagonal WS 2 requires precisely controlled conditions, and it is difficult to identify regions with different doping concentrations easily, which needs to rely on spectral recognition. In addition, the morphology of monolayer TMDCs is usually triangular rather than hexagonal, so it is necessary to explore the spatial distribution of triangular morphology of TMDCs domains that have uniform edge structures.…”

Section: Introductionmentioning

confidence: 99%

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Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Wang

Ding

et al. 2023

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The density and spatial distribution of substituted dopants affect the transition metal dichalcogenides (TMDCs) materials properties. Previous studies have demonstrated that the density of dopants in TMDCs increases with the amount of doping, and the phenomenon of doping concentration difference between the nucleation center and the edge is observed, but the spatial distribution law of doping atoms has not been carefully studied. Here, it is demonstrated that the spatial distribution of dopants changes at high doping concentrations. The spontaneous formation of an interface with a steep doping concentration change is named concentration phase separation (CPS). The difference in the spatial distribution of dopants on both sides of the interface can be identified by an optical microscope. This is consistent with the results of spectral analysis and microstructure characterization of scanning transmission electron microscope. According to the calculation results of density functional theory, the chemical potential has two relatively stable energies as the doping concentration increases, which leads to the spontaneous formation of CPS. Understanding the abnormal phenomena is important for the design of TMDCs devices. This work has great significance in the establishment and improvement of the doping theory and the design of the doping process for 2D materials.

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Section: Resultsmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Wang

Ding

et al. 2023

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“…Strain introduced by a rapid shift from equilibrium growth conditions is the most plausible explanation for the observed shifts in the energy of and disorder in PL. However, we also sought to address the possibility that chemical doping may be responsible for the observed spatial variations in PL, as has recently been shown in CVD-grown TMDs . X-ray photoelectron spectroscopy (XPS) of salt-assisted 2D WSe 2 crystals grown on SiO 2 substrates shows no photoelectron signal from either Na 1s (expected at 1072 eV) or Cl 2p (expected at 198 eV) states (Figure S13).…”

Section: Resultsmentioning

confidence: 99%

“…However, we also sought to address the possibility that chemical doping may be responsible for the observed spatial variations in PL, as has recently been shown in CVD-grown TMDs. 52 X-ray photoelectron spectroscopy (XPS) of salt-assisted 2D WSe 2 crystals grown on SiO 2 substrates shows no photoelectron signal from either Na 1s (expected at 1072 eV) or Cl 2p (expected at 198 eV) states (Figure S13). These data indicate that neither Na nor Cl is incorporated into the crystal lattice or adsorbed onto its surface after reaction.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Controlling Morphology and Excitonic Disorder in Monolayer WSe₂ Grown by Salt-Assisted CVD Methods

Dziobek-Garrett,

Hilliard,

Sriramineni

et al. 2023

ACS Nanosci. Au

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Chemical synthesis is a compelling alternative to topdown fabrication for controlling the size, shape, and composition of two-dimensional (2D) crystals. Precision tuning of the 2D crystal structure has broad implications for the discovery of new phenomena and the reliable implementation of these materials in optoelectronic, photovoltaic, and quantum devices. However, precise and predictable manipulation of the edge structure in 2D crystals through gas-phase synthesis is still a formidable challenge. Here, we demonstrate a saltassisted low-pressure chemical vapor deposition method that enables tuning W metal flux during growth of 2D WSe 2 monolayers and, thereby, direct control of their edge structure and optical properties. The degree of structural disorder in 2D WSe 2 is a direct function of the W metal flux, which is controlled by adjusting the mass ratio of WO 3 to NaCl. This edge disorder then couples to excitonic disorder, which manifests as broadened and spatially varying emission profiles. Our work links synthetic parameters with analyses of material morphology and optical properties to provide a unified understanding of intrinsic limits and opportunities in synthetic 2D materials.

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“…The peaks of in-plane vibration (E 2g ) and out-of-plane vibration (A 1g ) modes located at 350.8 cm −1 and 416.9 cm −1 are observed, respectively, which are consistent with the monolayer WS 2 . [35][36][37][38][39] It is to be noted that the A 1g peak is shifted from 416.9 (pristine WS 2 ) to 418.7 cm −1 (WS 2 (Er/Yb)), which could be attributed to the Er 3+ /Yb 3+ ions doping. [21] In addition, the Raman peak intensities of the WS 2 (Er/Yb) are approximately 2.5 times enhanced compared with those of the pristine WS 2 , implying the more active molecular vibration of WS 2 (Er/Yb).…”

Section: Resultsmentioning

confidence: 99%

Supersensitive and Broadband Photodetectors Based on High Concentration of Er³⁺/Yb³⁺ Co‐doped WS₂ Monolayer

Liu,

Zhao,

Huang

et al. 2023

Advanced Optical Materials

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Chemical doping is a significant means to modulate bandgap structures and optoelectronic properties of transition metal dichalcogenides (TMDCs). Herein, an Er3+/Yb3+ co‐doped WS2 monolayer with ultrahigh and tunable concentrations is successfully fabricated by in‐situ chemical vapor deposition (CVD) technique. The morphologies, thicknesses, components, and structures of the samples are systemically characterized by optical microscope, atomic force microscopy, Raman, X‐ray diffraction, X‐ray photoelectron spectroscopy, scanning electron microscope with energy dispersive spectrometer, and high‐resolution transmission electron microscopy, respectively. Photoluminescent peaks are enhanced significantly with red shifts, and the absorption is broadened to near‐infrared, implying a shrinked bandgap after RE co‐doping, which is consistent to the calculation results by density functional theory (DFT). The Er3+/Yb3+ co‐doped WS2 device demonstrates high carrier mobility, photocurrent, photoresponsivity, external quantum efficiency, and specific detectivity, which are approximately two orders of magnitudes compared with those of the pristine WS2 device. The values of photoresponsivity and specific detectivity approach 4.8 × 104 A W−1 and 5.5 × 1014 Jones, respectively, at 20 V bias and 1.77 mW cm−2 luminescence, which may refresh the records as has been reported. The excellent performances of the WS2 photodetector prove the effectiveness of Er3+/Yb3+ co‐doping for practical application in optoelectronics.

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Spatial Control of Substitutional Dopants in Hexagonal Monolayer WS₂: The Effect of Edge Termination

Abstract: The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202205800.

Cited by 17 publications

References 56 publications

Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Controlling Morphology and Excitonic Disorder in Monolayer WSe₂ Grown by Salt-Assisted CVD Methods

Supersensitive and Broadband Photodetectors Based on High Concentration of Er³⁺/Yb³⁺ Co‐doped WS₂ Monolayer

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Spatial Control of Substitutional Dopants in Hexagonal Monolayer WS2: The Effect of Edge Termination

Abstract: The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/smll.202205800.

Cited by 17 publications

References 56 publications

Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Concentration Phase Separation of Substitution‐Doped Atoms in TMDCs Monolayer

Controlling Morphology and Excitonic Disorder in Monolayer WSe2 Grown by Salt-Assisted CVD Methods

Supersensitive and Broadband Photodetectors Based on High Concentration of Er3+/Yb3+ Co‐doped WS2 Monolayer

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Spatial Control of Substitutional Dopants in Hexagonal Monolayer WS₂: The Effect of Edge Termination

Controlling Morphology and Excitonic Disorder in Monolayer WSe₂ Grown by Salt-Assisted CVD Methods

Supersensitive and Broadband Photodetectors Based on High Concentration of Er³⁺/Yb³⁺ Co‐doped WS₂ Monolayer