Vapor–liquid assisted chemical vapor deposition of Cu ₂ X materials

2D Materials · 2022 · 8 citations

• Materials science
• Chemical physics
• Nanotechnology

Abstract Transition metal dichalcogenides (TMDs) are known for their layered structure and tunable functional properties. However, a unified understanding on other transition metal chalcogenides (i.e. M 2 X) is still lacking. Here, the relatively new class of copper-based chalcogenides Cu 2 X (X = Te, Se, S) is thoroughly reported. Cu 2 X are synthesized by an unusual vapor–liquid assisted growth on a Al 2 O 3 /Cu/W stack. Liquid copper plays a significant role in synthesizing these layered systems, and sapphire assists with lateral growth and exfoliation. Similar to traditional TMDs, thickness dependent phonon signatures are observed, and high-resolution atomic images reveal the single phase Cu 2 Te that prefers to grow in lattice-matched layers. Charge transport measurements indicate a metallic nature at room temperature with a transition to a semiconducting nature at low temperatures accompanied by a phase transition, in agreement with band structure calculations. These findings establish a fundamental understanding and thrust Cu 2 Te as a flexible candidate for wide applications from photovoltaics and sensors to nanoelectronics.

P₂S₅ Reactive Flux Method for the Rapid Synthesis of Mono- and Bimetallic 2D Thiophosphates M_2–<i>x</i>M′_<i>x</i>P₂S₆

Inorganic Chemistry · 2021 · 31 citations

• Chemistry
• Crystallography
• Inorganic chemistry

flux reactions were monitored in situ using variable-temperature powder X-ray diffraction to understand the formation reaction pathways. The phases were directly formed in a single step at approximately 375 °C. The work functions of the semiconducting materials were determined and ranged from 5.28 to 5.72 eV.

Au@MoS₂@WS₂ Core–Shell Architectures: Combining Vapor Phase and Solution-Based Approaches

The Journal of Physical Chemistry C · 2020 · 11 citations

• Materials science
• Nanotechnology
• Chemical engineering

Solution preparation provides a versatile platform to extend the applications of transition-metal dichalcogenides (TMDs) beyond those achievable with traditional vapor-based preparation methods. However, existing solution-based synthesis and exfoliation approaches present numerous challenges, including low-crystallinity material and incompatibility with complex geometries, particularly with respect to spatial control over interfacial regions. Perhaps interestingly, these disadvantages align well with some of the advantages of vapor phase synthesis. Here, we introduce a strategy that combines vapor phase deposition and solution chemistry to build TMD core–shell heterostructures housed in aqueous media and reap the benefits of both preparation methods. We report a new TMD core–shell heterostructure, Au@MoS2@WS2, with an Au nanoparticle core and MoS2 and WS2 shells and provide a means of suspending the structure in solution to allow for higher order patterning and ligand-based functionalization. High-resolution electron microscopy and Raman spectroscopy provide a detailed analysis of the structure and interfaces of the core–shell heterostructures. UV–vis, dynamic light scattering, and zeta potential measurements exhibit outstanding natural stability and monodispersity of Au@MoS2@WS2 in solution. As a proof of concept, the aqueous environment is utilized to both functionalize the core–shell heterostructures with electrostatic ligands and pattern them into desired configurations on a target substrate. This work harnesses the advantages of vapor phase preparation of nanomaterials and the functionality possible with aqueous suspension to expand future engineering and application opportunities of TMD heterostructures.

Enhanced ferroelectricity in ultrathin films grown directly on silicon

Nature · 2020 · 871 citations

• Materials science
• Optoelectronics
• Nanotechnology