Na₂SO₄-Regulated High-Quality Growth of Transition Metal Dichalcogenides by Controlling Diffusion

Abstract

The high diffusion rate of sulfur with respect to metal oxide creates precursors that deviate from the stoichiometric ratio, leading to poor growth controllability and defects in the as-grown transition metal dichalcogenides (TMDCs). The introduction of a sulfur precursor with a high melting point is a hopeful strategy to solve these problems. Here, we first introduce sodium sulfate (Na 2 SO 4 ) as a sulfur precursor, which plays roles in tuning diffusion of source precursors and balancing their mass flux based on the temperatureconfined decomposition of Na 2 SO 4 . We deduced the specific growth process by characterizing the composition of intermediates; the results show that emissions of sulfur and metal sources were synchronously released and spanning the entire growth stage. This temperature-controlled source-feeding system reduced the diffusion gap between sulfur and metal, which promoted a faster kinetics for reactions. Moreover, this method has the wide applicability for producing other TMDCs.

Gas‐Phase Alkali Metal‐Assisted MOCVD Growth of 2D Transition Metal Dichalcogenides for Large‐Scale Precise Nucleation Control

“…[22,[37][38][39] Na species were probably removed as vaporized Na 2 O, Na 2 SO 3 , or Na 2 S after a chemical reaction between molten Na 2 MoO 4 and S-containing admolecules (Figure S14, Supporting Information). [21,39,40] Small 2022, 18, 2106368…”

Synthesis of 2D α‐GeTe Single Crystals and α‐GeTe/WSe2 Heterostructures with Enhanced Electronic Performance

“…[ 39 ] Some literature reported that H 2 reacted with chalcogenides in sulfides and then promoted the growth of 2D TMDC nanoplates. [ 40 ]…”

Controlled Growth of Wafer-Scale Transition Metal Dichalcogenides with a Vertical Composition Gradient for Artificial Synapses with High Linearity

“…On the one hand, we use metal precursors (e.g., Pt, Nb, and Ru) with high melting points (>1200 °C), which can provide a steady feeding concentration of metal during the growth process due to their relatively low evaporation capacity at the growth temperature (700–850 °C) (Figure a). On the other hand, we use H 2 S as the non-metal precursor, which provides steady diffusion onto the substrate surface and thus forms a uniform feeding rather than the volcano-like feeding when a solid precursor (e.g., sulfur) is used (Figure b). − As the metal precursor has a steady feeding and is immobilized compactly on the substrate, the controllable feeding and diffusion of sulfur into the metal surface will finally result in a vertical composition gradient of sulfur. Consequently, wafer-scale and laterally uniform g-TMDCs could be prepared.…”