Facile and Controllable Synthesis of Large-Area Monolayer WS2 Flakes Based on WO3 Precursor Drop-Casted Substrates by Chemical Vapor Deposition

Abstract

Monolayer WS2 (Tungsten Disulfide) with a direct-energy gap and excellent photoluminescence quantum yield at room temperature shows potential applications in optoelectronics. However, controllable synthesis of large-area monolayer WS2 is still challenging because of the difficulty in controlling the interrelated growth parameters. Herein, we report a facile and controllable method for synthesis of large-area monolayer WS2 flakes by direct sulfurization of powdered WO3 (Tungsten Trioxide) drop-casted on SiO2/Si substrates in a one-end sealed quartz tube. The samples were thoroughly characterized by an optical microscope, atomic force microscope, transmission electron microscope, fluorescence microscope, photoluminescence spectrometer, and Raman spectrometer. The obtained results indicate that large triangular monolayer WS2 flakes with an edge length up to 250 to 370 μm and homogeneous crystallinity were readily synthesized within 5 min of growth. We demonstrate that the as-grown monolayer WS2 flakes show distinctly size-dependent fluorescence emission, which is mainly attributed to the heterogeneous release of intrinsic tensile strain after growth.

Enhanced Performance of Planar Perovskite Solar Cells Induced by Van Der Waals Epitaxial Growth of Mixed Perovskite Films on WS2 Flakes

“…It is notable that the lattice distance of the (020) plane for the mixed perovskite is 0.31 nm, [ 38 ] which is twice of the plane distance of (110) of WS 2 . [ 39 ] This lattice match would favor the epitaxial growth of the mixed perovskite on WS 2 flakes. As shown in Figure 3d, the SAED pattern of perovskite/WS 2 heterojunction shows two sets of diffraction patterns, which can be assigned to the bottom WS 2 (blue) and the top perovskite (red), respectively.…”

CVD controlled growth of large-scale WS2 monolayers

“…[22][23][24][25][26][27] The most utilized CVD process is the sulfurization of WO 3 powders in sulfur vapor. [27][28][29][30][31][32][33][34][35][36][37][38][39][40] However, the crystal quality was inuenced by various experimental parameters, such as metal catalyst, pressure, substrate, the time of S-precursor introduction, temperature and location of precursor and substrate, carrier gas ow, pretreatment of the precursor or not, and growth temperature. 33,[41][42][43] The growth mechanism is unclear and under discussing.…”

Emerging 2D Materials and Their Van Der Waals Heterostructures

“…The synthesis of large area and good quality TMDs is of paramount importance for their industrial exploitation. The fabrication of monolayer WS 2 flakes is the subject of the work of Shi and coworkers [61]. WS 2 has a structure similar to the best-known MoS 2 , but exhibits stronger photoluminescence quantum yield at room temperature and larger spin-orbit coupling and is a promising 2D material for applications in optoelectronics and spintronics.…”