Interfaces determine the nucleation and growth of large NbS<sub>2</sub> single crystals

Cheng, Zhaofang; He, Shaodan; Han, Xijiang; Wang, Min; Zhang, Shimin; Liu, Shiru; Liang, Gongying; Zhang, Shengli; Xia, Minggang

doi:10.1039/d0ce01393e

Cited by 5 publications

(8 citation statements)

References 37 publications

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“…The exact nature of the entire set of chemical, crystallization, and growth processes of the liquid precursor-intermediated CVD approach is not yet fully understood [44,63]. We presume that it is similar to the model proposed recently for Na 2 WO 4 [33] (Mo [64,65], Nb [66]) complexes within the framework of the vapor-liquid-solid mechanism for TMDC, where the eutectic precursor phase/substrate interface [66] and thermodynamic nucleation evolution [67,68] play key roles.…”

Section: Precursor Deposition and Cvd Synthesis Proceduressupporting

confidence: 52%

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Buchkov,

Rafailov,

Minev

et al. 2024

Crystals

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Owing to their exceptional properties, which are usually determined by the growth conditions, 2D transition metal dichalcogenides (TMDCs) offer numerous research directions for applications in the fields of spintronics, valleytronics, and optoelectronics. Here, we focus on the chemical vapor deposition (CVD) synthesis of WSe2 (tungsten diselenide) nanoclusters/nanoflakes by using a liquid precursor for tungsten (ammonium metatungstate) on Si/SiO2, fused silica, and sapphire substrates. Various WSe2 clusters with different sizes, thicknesses, and geometries were analyzed by means of optical and atomic force microscopy (AFM) and Raman spectroscopy. The observed structures were mostly WSe2 multilayers; however, monolayer formations were also found. They showed significant morphological differences, as well as wide nucleation density and size variations, possibly related to precursor/substrate surface interactions under the same CVD synthesis conditions. The largest WSe2 domains with a lateral size of up to hundreds of micrometers were observed on sapphire, probably caused by a higher growth rate of singular nucleation sites. WSe2 domains with irregular and triangular shapes were simultaneously identified on fused silica, whereas multilayered pyramidal WSe2 structures dominated in the case of Si/SiO2 substrates. The application of polarized Raman spectroscopy to precisely determine and differentiate the characteristic vibrational modes (A1g, E2g, and 2LA(M)) enabled the unambiguous identification of 2D and/or multilayered WSe2 formations with a high crystallinity level. The presented comparative analysis of samples prepared in relatively simple synthesis conditions (moderate working temperatures and ambient pressure) provides a base for further progress of the facile metatungstate CVD method and relevant opportunities for the exploration of 2D TMDC materials.

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Section: Precursor Deposition and Cvd Synthesis Proceduressupporting

confidence: 52%

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Buchkov,

Rafailov,

Minev

et al. 2024

Crystals

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“…Subsequently, these MoS x monomers continuously diffuse to the liquid− substrate interface to form MoS 2 single crystals, followed by the continuous epitaxial growth of monolayer MoS 2 . 30 When the temperature is increased to 800 °C after completing the MoS 2 growth at 700 °C, Nb-doped WS 2 starts to grow from the edge of MoS 2 to form a lateral heterostructure. Because of the low chemical reactivity of WO 3 and Nb 2 O 5 , a Nb•WS 2 outer layer forms when the temperature increases to 800 °C (Figure S4a), while no outer layer can be observed when the temperature is maintained at 700 °C (Figure S4b).…”

Section: Resultsmentioning

confidence: 99%

“…Sulfur vapor is absorbed on the surface of the liquid droplets to facilitate MoS 2 nucleation as MoS x monomers at the liquid–substrate interface. Subsequently, these MoS x monomers continuously diffuse to the liquid–substrate interface to form MoS 2 single crystals, followed by the continuous epitaxial growth of monolayer MoS 2 . When the temperature is increased to 800 °C after completing the MoS 2 growth at 700 °C, Nb-doped WS 2 starts to grow from the edge of MoS 2 to form a lateral heterostructure.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of a Selectively Nb-Doped WS₂–MoS₂ Lateral Heterostructure for a High-Detectivity PN Photodiode

Phan

et al. 2022

ACS Nano

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In this study, selective Nb doping (P-type) at the WS 2 layer in a WS 2 −MoS 2 lateral heterostructure via a chemical vapor deposition (CVD) method using a solution-phase precursor containing W, Mo, and Nb atoms is proposed. The different chemical activity reactivity (MoO 3 > WO 3 > Nb 2 O 5 ) enable the separation of the growth temperature of intrinsic MoS 2 to 700 °C (first grown inner layer) and Nb-doped WS 2 to 800 °C (second grown outer layer). By controlling the Nb/(W+Nb) molar ratio in the solution precursor, the hole carrier density in the p-type WS 2 layer is selectively controlled from approximately 1.87 × 10 7 /cm 2 at 1.5 at.% Nb to approximately 1.16 × 10 13 / cm 2 at 8.1 at.% Nb, while the electron carrier density in n-type MoS 2 shows negligible change with variation of the Nb molar ratio. As a result, the electrical behavior of the WS 2 −MoS 2 heterostructure transforms from the N−N junction (0 at.% Nb) to the P−N junction (4.5 at.% Nb) and the P−N tunnel junction (8.1 at.% Nb). The band-toband tunneling at the P−N tunnel junction (8.1 at.% Nb) is eliminated by applying negative gate bias, resulting in a maximum rectification ratio (10 5 ) and a minimum channel resistance (10 8 Ω). With this optimized photodiode (8.1 at.% Nb at V g = −30 V), an I photo /I dark ratio of 6000 and a detectivity of 1.1 × 10 14 Jones are achieved, which are approximately 20 and 3 times higher, respectively, than the previously reported highest values for CVD-grown transition-metal dichalcogenide P−N junctions.

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“…This process is similar to a previously reported finding. 39,40 Given that the formation energy of the MoS 2 monolayer (2.48 eV) is lower than that of VS 2 (2.79 eV), 41 the formation of MoS 2 dominated, and trace amounts of V atoms were embedded in the MoS 2 layer in the form of doping. The molten droplet, as a metal precursor, was constantly consumed and decreased in volume during growth.…”

Section: Resultsmentioning

confidence: 99%

“…S5), we established a two-dimensional simplified model to analyze the growth rates of V atoms in VLS and VS modes respectively. 39 Fig. 4(b) shows the simulation results of the V-atom doping rate in VLS and VS modes.…”

Section: Resultsmentioning

confidence: 99%

Manipulation of the 1T-MoS₂ domain in a 2H-MoS₂ main phase induced by V-doping via a CVD vapor–liquid–solid mechanism

Cheng

Xin

et al. 2022

CrystEngComm

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Interfaces determine the nucleation and growth of large NbS₂ single crystals

Abstract: The synthesis of large NbS2 single crystals benefits from Na–Nb–O droplet interfaces, which reduces nucleation density and increases growth rate.

Cited by 5 publications

References 37 publications

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Synthesis of a Selectively Nb-Doped WS₂–MoS₂ Lateral Heterostructure for a High-Detectivity PN Photodiode

Manipulation of the 1T-MoS₂ domain in a 2H-MoS₂ main phase induced by V-doping via a CVD vapor–liquid–solid mechanism

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Interfaces determine the nucleation and growth of large NbS2 single crystals

Abstract: The synthesis of large NbS2 single crystals benefits from Na–Nb–O droplet interfaces, which reduces nucleation density and increases growth rate.

Cited by 5 publications

References 37 publications

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Metatungstate Chemical Vapor Deposition of WSe2: Substrate Effects, Shapes, and Morphologies

Synthesis of a Selectively Nb-Doped WS2–MoS2 Lateral Heterostructure for a High-Detectivity PN Photodiode

Manipulation of the 1T-MoS2 domain in a 2H-MoS2 main phase induced by V-doping via a CVD vapor–liquid–solid mechanism

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Interfaces determine the nucleation and growth of large NbS₂ single crystals

Synthesis of a Selectively Nb-Doped WS₂–MoS₂ Lateral Heterostructure for a High-Detectivity PN Photodiode

Manipulation of the 1T-MoS₂ domain in a 2H-MoS₂ main phase induced by V-doping via a CVD vapor–liquid–solid mechanism