Skipping ahead in a line is rude, but sometimes it is acceptable. Especially for salt.
In its follow-up study, the Rice University lab of materials theorist Boris Yakobson shows how salt simplifies the formation of valuable 2D molybdenum disulfide with a first-principles analysis of the process that could refine it even further.
The simulation of atom-level energies shows that salt is particularly iodized.
It helps to skip some steps and jump high energy barriers in conventional CVD growth to yield far more MoS 6 and 2D MoS 2.
Their study focused on how salt lowers activation barriers to enhance the sulfurization of Molybdenum oxyhalides, the gas source in MoS 2 crystallization.
MoS 2 is a natural compound known in bulk form as molybdenite, and in 2D form is highly coveted for its semiconducting properties. It is hard to make 2D MoS 2 in commercial quantities.
The Rice team first entered the competition when labs in Singapore, China, Japan and Taiwan used salt to make 2D materials that combined transition metals and chalcogens. Why it worked so well was a mystery, prompting them to call upon the Yakobson lab's expertise in modeling materials from the ground up.
The international labs use chloride salts to make their library of materials, but the iodide salts found on kitchen tables are better at speeding up the synthesis of MoS 2.
The widespread application of MoS 2 requires fast and large-scale synthesis. One could make MoS 2 much faster by simply changing chloride to iodide.
When salt and the precursor form a eutectic, a mixture of substances that melt and solidify at a single temperature that is lower than the melting points of the constituents, it happens.
After salt-assisted synthesis was shown to enable the growth of many more TMD compounds than was possible before, it became clear that there is something special about this process.
She said that monitoring the gas phase under growth conditions is not a simple task.
We were very thorough in following up on the work of Jincheng. We did a simulation of the entire process, from sulfurization to the 2D crystal growth. This approach paid off.
The Rice team observed the entire sulfurization process as oxygen and chlorine atoms were gradually replaced by sulfur in MoO 2.
The eutectic effect may be a common phenomenon in the CVD synthesis of 2D dichalcogenide monolayers.
More information: Jincheng Lei et al, Salt-Assisted MoS2 Growth: Molecular Mechanisms from the First Principles, Journal of the American Chemical Society (2022). DOI: 10.1021/jacs.2c02497 Journal information: Journal of the American Chemical Society Citation: Study details why 2D molybdenum disulfide formation gets a speed boost from salt (2022, April 18) retrieved 18 April 2022 from https://phys.org/news/2022-04-2d-molybdenum-disulfide-formation-boost.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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