Synthesis of Atomically Thin Transition Metal Ditelluride Films by Rapid Chemical Transformation in Solution Phase

Giri, Anupam; Yang, Hee-Seung; Jang, Woosun; Kwak, Joon Seop; Thiyagarajan, Kaliannan; Pal, Monalisa; Lee, Dong-Hyun; Singh, Ranbir; Kim, Chulhong; Cho, Kilwon; Soon, Aloysius; Jeong, Unyong

doi:10.1021/acs.chemmater.8b00684

Cited by 25 publications

(20 citation statements)

References 52 publications

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“…MoTe 2 thin films were prepared on a Si wafer by a quick microwave assisted synthetic process. [33,34] The MoTe 2 -deposited substrate was stacked face down on the metal-deposited wafer without any gap in-between. The stacked specimen was placed in a single-zone rapid thermal annealing (RTA) chamber (chamber volume ≈ 630 mL), then thermally annealed for 3 min under continuous flow of a mixture of argon and hydrogen gas (Ar: H 2 = 95: 5, flow rate = 55 000 sccm).…”

Section: Growth Of Ternary Metal Chalcogenidesmentioning

confidence: 99%

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Giri

Kumar

et al. 2021

Advanced Materials

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non-vdW crystals (such as Mn 3 Si 2 Te 6, [12,13] ) has led to an interesting arena for studying fundamental 2D magnetism and provided numerous opportunities for 2D magnetic, magnetoelectric, and magnetooptic applications. [14,15] Electrical control of both charge and spin degrees of freedom in 2D ferromagnetic semiconductors is an important step in creating novel spintronic devices. As a single integrated platform, the spintronic devices based on these materials are expected to complement or outperform (in some cases) the conventional semiconductor-based devices. [16] However, compared to binary 2D metal chalcogenides, synthesis of ternary 2D metal chalcogenides is far more challenging, so the proof-of-concept studies on the magnetoelectric phenomena of the ferromagnetic ternary 2D metal chalcogenides have been performed on thin flakes mechanically exfoliated from bulk crystals. [9,17] There have been limited reports on the synthesis of ferromagnetic 2D ternary metal chalcogenide thin films. [18,19] The synthesis from pure elemental mixtures in an evacuated quartz ampule at 900-1100 °C through the self-flux of elements took 5-20 days. [7,13,17,20] Only two types of thin films have been synthesized via molecular beam epitaxy (MBE) in an ultra-high vacuum condition. [21][22][23] Very recently, a few CVD-based synthesis have been reported for binary 2D metal chalcogenide magnetic crystals such as CrSe and FeTe. [24,25] However, to the best of our knowledge, the conventional CVD-based and Following the first experimental realization of intrinsic ferromagnetism in 2D van der Waals (vdW) crystals, several ternary metal chalcogenides with unprecedented long-range ferromagnetic order have been explored. However, the synthesis of large-area 2D ternary metal chalcogenide thin films is a great challenge, and a generalized synthesis has not been demonstrated yet. Here, a quick and scalable synthesis of epitaxially aligned ferromagnetic ternary metal chalcogenide thin films (Cr 2 Ge 2 Te 6 , Cr 2 Si 2 Te 6 , Mn 3 Si 2 Te 6 ) is reported. The synthesis is based on the flux-controlled surface diffusion of Te on metal (Cr, Mn)-deposited wafer (Ge, Si) substrates. Magnetic anisotropy study of the epitaxial ternary thin films reveals the intrinsic magnetic easy axis; out-of-plane direction for Cr 2 Ge 2 Te 6 and Cr 2 Si 2 Te 6 , and in-plane direction for Mn 3 Si 2 Te 6 . In addition to the synthesis, this work creates an opportunity for transfer-free device fabrication for realizing magnetoelectronics based on the electrical control of both charge and spin degrees of freedom in 2D ferromagnetic semiconductors.

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Section: Growth Of Ternary Metal Chalcogenidesmentioning

confidence: 99%

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Giri

Kumar

et al. 2021

Advanced Materials

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“…A number of other works have synthesised WTe 2 on the nanoscale using methods such as solution-based growth and molecular beam epitaxy (MBE) [26,48,53]. The work on beam-interrupted MBE synthesis of WTe 2 demonstrates the growth of large-area and high-quality films with a high degree of thickness control, making it a promising choice for synthesis of WTe 2 .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of tungsten ditelluride thin films and highly crystalline nanobelts from pre-deposited reactants

et al. 2020

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Tungsten ditelluride (WTe 2) is a layered transition metal dichalcogenide (TMD) that has attracted increasing research interest in recent years. WTe 2 has demonstrated large non-saturating magnetoresistance, potential for spintronic applications and promise as a type-II Weyl semimetal. The majority of works on WTe 2 have relied on mechanically exfoliated flakes from chemical vapour transport (CVT)-grown crystals for their investigations. While producing high-quality samples, this method is hindered by several disadvantages including long synthesis time, high-temperature annealing and an inherent lack of scalability. In this work, a synthesis method is demonstrated that allows the production of large-area polycrystalline films of WTe 2. This is achieved by the reaction of pre-deposited films of W and Te at a relatively low temperature of 550 °C. Sputter X-ray photoelectron spectroscopy reveals the rapid but self-limiting nature of the oxidation of these WTe 2 films in ambient conditions. The WTe 2 films are composed of areas of micrometre-sized nanobelts that can be isolated and offer potential as an alternative to CVT-grown samples. These nanobelts are highly crystalline with low defect densities indicated by transmission electron microscopy and show promising initial electrical results.

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“…However, mechanical exfoliation does not provide control over the thickness, size, or shape of the flakes, and the yield is low. Recent synthesis efforts have shown MoTe 2 monolayer flakes that are a few microns in size. , Large-area thin films of MoTe 2 have been demonstrated using molecular beam epitaxy, chemical vapor deposition, ,− and solution-phase synthesis, albeit for a limited range of thicknesses. Robust growth results of MoTe 2 thin films from monolayer to any arbitrary thickness with large grains have yet to be demonstrated.…”

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confidence: 99%

cm²-Scale Synthesis of MoTe₂ Thin Films with Large Grains and Layer Control

Hynek

Singhania

et al. 2020

ACS Nano

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Owing to the small energy differences between its polymorphs, MoTe2 can access a full spectrum of electronic states, from the 2H semiconducting state to the 1T′ semimetallic state, and from the Td Weyl semimetallic state to the superconducting state in the 1T′ and Td phase at low temperature. Thus, it is a model system for phase transformation studies as well as quantum phenomena such as the quantum spin Hall effect and topological superconductivity. Careful studies of MoTe2 and its potential applications require large-area MoTe2 thin films with high crystallinity and thickness control. Here, we present cm 2 -scale synthesis of 2H-MoTe2 thin films with layer control and large grains that span several microns. Layer control is achieved by controlling the initial thickness of the precursor MoOx thin films, which are deposited on sapphire substrates by atomic layer deposition and subsequently tellurized. Despite the van der Waals epitaxy, the precursor-substrate interface is found to critically determine the uniformity in thickness and grain size of the resulting MoTe2 films: MoTe2 grown on sapphire show uniform films while MoTe2 grown on amorphous SiO2 substrates form islands. This synthesis strategy decouples the layer control from the variabilities of growth conditions for robust growth results, and is applicable to grow other transition metal dichalcogenides with layer control.

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Synthesis of Atomically Thin Transition Metal Ditelluride Films by Rapid Chemical Transformation in Solution Phase

Cited by 25 publications

References 52 publications

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Synthesis of tungsten ditelluride thin films and highly crystalline nanobelts from pre-deposited reactants

cm²-Scale Synthesis of MoTe₂ Thin Films with Large Grains and Layer Control

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Synthesis of Atomically Thin Transition Metal Ditelluride Films by Rapid Chemical Transformation in Solution Phase

Cited by 25 publications

References 52 publications

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Large‐Area Epitaxial Film Growth of van der Waals Ferromagnetic Ternary Chalcogenides

Synthesis of tungsten ditelluride thin films and highly crystalline nanobelts from pre-deposited reactants

cm2-Scale Synthesis of MoTe2 Thin Films with Large Grains and Layer Control

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cm²-Scale Synthesis of MoTe₂ Thin Films with Large Grains and Layer Control