Sodium-Mediated Low-Temperature Synthesis of Monolayers of Molybdenum Disulfide for Nanoscale Optoelectronic Devices

Abstract

Monolayers of molybdenum disulfide are of vital importance in the fabrication of optical and nanoelectronic devices. The development of thin and low-cost devices has increased the demand for synthesis processes. Usually, the synthesis of molybdenum disulfide monolayers requires temperatures of approximately 800 °C, which is a drawback for the applications mentioned above. Here, we propose a route using the atmospheric pressure chemical vapor deposition technique to grow monolayers of MoS2 at 550 °C mediated by using sodium as a catalyst. We produced single crystals and polycrystalline films by controlling the NaNO3/MoO3 catalyst/precursor ratio and the growth time. Using first-principles calculations, we determined that sodium was the nucleation site of the growth process. The precursor’s ratio is crucial to decrease the formation energy and the synthesis temperature. First-principles calculations and experiments showed that the ideal precursor ratio was 0.3 and that the synthesis temperature should be decreased by 250 °C. We investigated the monolayers with optical microscopy, high-resolution scanning transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, Raman spectroscopy, photoluminescence spectroscopy, and transport experiments. The optical and electrical performances were comparable to those of monolayers grown at higher temperatures. We believe that a low-temperature synthesis recipe is essential to drive the fabrication of nanoscale optoelectronic devices.

Synthesis of WS2 by Chemical Vapor Deposition: Role of the Alumina Crucible

“…It nearly triples after the ninth growth cycle (from 1 at.% to 4 at.%). It is well known that sodium acts as a catalyst in the growth of WS 2 via CVD [39]. From first-principles calculations, sodium was the nucleation site of the growth process, and the amount of sodium is crucial to decreasing the formation energy of TMDs [40,41].…”

A Unified Theory for H2 Evolution on Mo-Based Electrocatalysts

“…This prepared MoS 2 consisted of the pure 2H phase with a small population of defects as determined by Raman spectroscopy (Figure S5). 38 However, the presence of defects did not translate to a significant amount of reducible Mo 4+ as the Mo 4+/3+ reduction peak was small in comparison to other catalysts. This crystalline material subsequently demonstrated poor activity for the HER compared to a-MoS x , similarly to previously studied defect-free crystalline epitaxial MoS 2 .…”

Additive‐Assisted Growth of Scaled and Quality 2D Materials

“…They concluded that the usage of NaCl could passivate the defect sites during the growth process, thus further elevate the emission of excitons. In another work, Safeer et al [ 90 ] even decreased the growth temperature of MoS 2 to 550 °C mediated by NaNO 3 as a catalyst. They determined that sodium played the function of nucleation site during the growth.…”

“…Figure 14e shows that centimeter‐scale domains could be achieved with the addition of KOH. Similarly, Kim et al [ 90 ] utilized alkali halides to assist the growth of MoS 2 , which could modulate the water concentration with suppressed nucleation and encourage the growth of 2D materials.…”