Centimeter-Scale Synthesis of Monolayer WS₂ Using Single-Zone Atmospheric-Pressure Chemical Vapor Deposition: A Detailed Study of Parametric Dependence, Growth Mechanism, and Photodetector Properties

Abstract

Two-dimensional transition metal dichalcogenides offer exciting opportunities to tailor their electrical and optoelectronic properties, which provide them with a multitude of applications, following which their large-area synthesis holds high significance. Herein, we demonstrate NaCl-assisted centimeter-scale (1.5 × 1 cm 2 ) growth of monolayer WS 2 using an atmospheric-pressure chemical vapor deposition technique. We attempt to explicate the growth mechanism with the Volmer− Weber, Stranski−Krastanov, and Frank−van der Merwe modes by incorporating the importance of NaCl as a growth promoter and other parameters like the quantity of sulfur, temperature, gas flow rate, and hold time. The parameters optimized for large-area monolayer growth were found at a NaCl to WO 3 w/w ratio of 1:2 and a sulfur to WO 3 w/w ratio of 3:1, with a 1 min hold time at 820 °C in a 120 sccm argon gas flow. The optical microscope images along with the corresponding Raman and photoluminescence spectra were employed to examine the growth of the WS 2 film at different sets of synthesis parameters. The photodetector fabricated on the as-grown film showed a high responsivity and specific detectivity of 4.27 mA/W and 1.27 × 10 10 Jones, respectively, in the visible region and 261 mA/W and 7.72 × 10 11 Jones, respectively, in the ultraviolet (UV) region. These results support its application in UV−visible photodetection.

CuBi2O4nanocrystals integrated with polyaniline nanobelt arrays for weak light photomultiplication type photodetector

“…We must still construct a reliable, low-cost, low-dark current and self-driven photodetector. 18,24,25 Using CuBi 2 O 4 deposited on n-Si and a p-n heterojunction, Zewei Wu et al recently created a photodetector that shows a remarkable photoresponsivity of 1.69 × 10 4 mA W −1 at an applied bias of zero potential. 21 CuBi 2 O 4 is a newly developed p-type semiconductor that is intended to be used as a photocathode in the photoelectric synthesis of solar fuel.…”

Tailoring the Vertical and Planar Growth of 2D WS2 Thin Films Using Pulsed Laser Deposition for Enhanced Gas Sensing Properties

“…Bulk WS 2 has an indirect band gap of 1.3 eV, while the monolayer has a direct band gap of ∼2 eV . It has shown potential application in photovoltaics, photodetectors, hydrogen evolution reaction (HER), field effect transistors (FETs), gas sensing, biosensing, lubricants, batteries, supercapacitors, and memristors …”

“…Bulk WS 2 has an indirect band gap of 1.3 eV, while the monolayer has a direct band gap of ∼2 eV. 3 It has shown potential application in photovoltaics, 4 photodetectors, 5 hydrogen evolution reaction (HER), 6 field effect transistors (FETs), 7 gas sensing, 8 biosensing, 9 lubricants, 10 batteries, 11 supercapacitors, 12 and memristors. 13 One of the major challenges in the development and commercialization of 2D materials is to scale up their growth to a large area with controllable thickness, crystallinity, uniformity, morphology, phase, and crystallite orientation.…”

Photocurrent conversion capability of a 2D WS2-polyvinyl alcohol matrix and its DFT-based charge carrier dynamics analysis

“…This result is very close to the previously reported PVA/CQD-based device responsivity of 0.26 A W À1 . 54 According to relation (10), the gain of a photoconductor is equal to the minority carrier recombination lifetime divided by the time the carriers need to travel across the semiconductor between the two contacts of the device. Given that the transit time is significantly less than the recombination lifetime, a photoconductor will inevitably experience a considerable gain.…”

“…Due to their unique features, TMDCs have received a lot of interest and have been suggested as prospective candidate for photonic and optoelectronic devices. 9–11…”