Recent progress in the CVD growth of 2D vertical heterostructures based on transition-metal dichalcogenides

Abstract

This review summarizes recent advances in the controllable CVD growth of 2D TMDC vertical heterostructures under four different strategies.

Controllable Synthesis of Large-Scale Monolayer MoS2 Dendritic Flakes with Serrated Edges and Their Multimodal Microscopy and AFM Characterizations

“…The Raman spectra of the five different points, which are located at the branches and the very center of the flake, in Figure 3b have two characteristic Raman peaks of typical 2H-MoS 2 , E 2g 1 (∼382 cm −1 ) and A 1g (∼402 cm −1 ). 18,32 The E 2g 1 peak corresponds to the in-plane vibration mode and is preferentially excited for terrace terminations, whereas the A 1g mode is related to the out-of-plane vibration mode and is preferentially excited for edge terminations. 23 The corresponding intensity ratio of A 1g /E 2g 1 can therefore be employed to transmit valuable information on the texture of MoS 2 , 13,33 and the integrated intensity ratios of A 1g /E 2g 1 from points 1 → 5 are 1.12, 1.01, 1.03, 1.09, and 0.96, which presents a slight fluctuation compared with that of the reported value of the MoS 2 monolayer (A 1g /E 2g 1 ≈ 1).…”

“…Controllable growth is especially critical to realizing the high-yield fabrication of high-quality 2D TMDC materials via a bottom-up approach including chemical vapor deposition (CVD), molecular beam epitaxy (MBE), and pulsed laser deposition (PLD), which demand a deep understanding of the growth mechanism during sequential growth stages, for example, precursors evaporation/decomposition/transport, adsorption and diffusion of adatoms, nucleation, attachment, and detachment to the growth frontier. − Generally, the growth process of 2D flakes/films by vapor deposition is a nonequilibrium process largely controlled by the competition between kinetics and thermodynamics, which is influenced by diverse growth factors, such as the growth temperature, gas flow rate, growth pressure, etc. , Therefore, it is truly crucial to balance various growth factors to achieve the controllable growth of 2D TMDC materials.…”

“…15−17 Generally, the growth process of 2D flakes/films by vapor deposition is a nonequilibrium process largely controlled by the competition between kinetics and thermodynamics, which is influenced by diverse growth factors, such as the growth temperature, gas flow rate, growth pressure, etc. 18,19 Therefore, it is truly crucial to balance various growth factors to achieve the controllable growth of 2D TMDC materials. Recently, considerable effort has been devoted to developing high-yield and large-sized monolayer MoS 2 crystals for electrocatalysis by increasing the density of active sites and vacancies, 20,21 phase engineering, 12 and doping, 22 and CVD has been demonstrated to be the most versatile method to attain 2D MoS 2 crystals with the desired configuration suitable for electrocatalysis.…”

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

“…10−12 The heterostructures are commonly constructed by vertically stacking exfoliated (s-TMD) layers using mechanical transfer techniques, which have the problems of uncontrolled stacking angle, interfacial contamination, and low mass production. 13 Recently, the chemical vapor deposition (CVD) method has been found to be effective for the synthesis of lateral TMD heterostructures with large-scale production and clean interfaces. The lateral heterostructures generated through an epitaxial stitch at the 1D edge of s-TMD domains possess a sharp interface, which makes it possible to study quantum transport at the 1D nanoscale, in addition to providing a high surface energy transfer efficiency.…”

“…Semiconducting transition-metal dichalcogenides (s-TMDs), such as MoS 2 , WS 2 , MoSe 2 , and WSe 2 , have attracted tremendous attention owing to their excellent electrical and optical properties. − Vertical and lateral s-TMD heterostructures have been created in atomically thin devices to explore new electronic and photonic properties based on band structure engineering. − The heterostructures are commonly constructed by vertically stacking exfoliated (s-TMD) layers using mechanical transfer techniques, which have the problems of uncontrolled stacking angle, interfacial contamination, and low mass production . Recently, the chemical vapor deposition (CVD) method has been found to be effective for the synthesis of lateral TMD heterostructures with large-scale production and clean interfaces.…”