Abstract
Van der Waals heterostructures are the fundamental building blocks of electronic and optoelectronic devices. Here we report that, through a single-step chemical vapour deposition (CVD) process, high-quality vertical bilayer MoS2/WS2 heterostructures with a grain size up to ∼60 μm can be synthesized from molten salt precursors, Na2MoO4 and Na2WO4. Instead of normal pyramid vertical heterostructures grown by CVD, this method synthesizes an anti-pyramid MoS2/WS2 structure, which is characterized by Raman, photoluminescence and second harmonic generation microscopy. Our facile CVD strategy for synthesizing anti-pyramid structures unveils a new synthesis route for the products of two-dimensional heterostructures and their devices for application.
Highlights
Two-dimensional (2D) materials are a series of crystalline materials with a thickness at atomic scale, such as graphene, transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN) and other materials
To grow the MoS2/WS2 heterostructure, 5 mg mL−1 Na2MoO4 and Na2WO4 are firstly spin-coated on two sapphire or SiO2/Si substrates, respectively
The AA′-stacking with an anti-pyramid order is demonstrated by different techniques, including Raman, PL, atomic force microscopy (AFM) and Second harmonic generation microscopy (SHG) microscopy
Summary
Two-dimensional (2D) materials are a series of crystalline materials with a thickness at atomic scale, such as graphene, transition metal dichalcogenides (TMDs), hexagonal boron nitride (h-BN) and other materials Due to their unique properties, these 2D materials are expected to play important roles in future electronics, optoelectronics and photonics.[1,2,3,4,5,6] By vertically stacking different 2D materials, various 2D van der Waals heterostructures (2D heterostructures) have been demonstrated showing improved performance or even completely novel properties, and potential for various applications.[7,8,9,10] For example, by the stacking of graphene, h-BN and MoS2 as a heterostructure, Withers et al have achieved light emitting diodes with a quantum efficiency of 8.4%,11 while monolayer MoS2 based light emitting diodes typically only have that of less than 1%.12,13. By carefully choosing the precursors, we demonstrated a versatile, reproducible one-step growth method for the 2D TMD heterostructures without any additional promoters This is the first report of fabrication of a vertical anti-pyramid heterostructure by the CVD growth method. Micro-Raman and photoluminescence (PL) spectroscopy, atomic force microscopy (AFM), as well as non-linear optical spectroscopy are used to fully characterize the structural and optical qualities of the assynthesized heterostructures
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