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Fast and efficient catalyst to scoot tellurium in place of sulfur, and convert 2-D MoS2 to MoTe2 at low temperature

January 30th, 2018
'Sodium-scooter' delivers
New tellurization process for MoS2 developed in this study. a) A NaOH substrate and a MoS2 sample face each other and create MoTe2. b) Most likely, NaOH in the presence of Te vapors converts to Na2Te, which is scooted to the MoS2 substrate to exchange Te with S atoms. c) The Na-scooter reduced the energy required for the reaction. Credit: IBS

Korean food delivery systems are known to be fast and efficient. Scooters speed through the city to bring timely orders to the doorstep. Researchers at the Institute for Basic Science (IBS, South Korea) have developed a low-temperature reaction, where a "chemical scooter delivery" can be used as a metaphor. A "sodium-scooter", namely Na2Te, transports tellurium to molybdenum disulfide (MoS2) and tungsten disulfide (WS2) monolayers. With the help of the scooter, sulfur atoms were replaced with tellurium. The process occurs at 525 °C, about 300 °C lower than previously achievable. This study, published in Nature Communications, is expected to facilitate the exploration of new properties in these 2D materials.

"We call it scooter, because it delivers quickly. MoTe2 molecules decompose to molybdenum and tellurium at high temperatures, but the scooter anchors telluride to MoS2 and acts as a catalyst that lowers the activation temperature of the reaction," explains YUN Seok Joon, the first author of the study.

Using this approach, the research team prepared semiconducting molybdenum ditelluride (2H-MoTe2), metallic 1T'-MoTe2, MoS2xTex and WS2xTex alloys. The conversion which began at the edges and grain boundaries of MoS2, was complete. 2H-MoTe2 formed near the edge and is favored at low temperatures, while 1T'-MoTe2 at high temperatures. In this method, the team could produce a diode with 2H-MoTe2 on the edge and 2H-MoS2 on the inner part. The resulting materials had different bandgap (1.1 eV), and higher degree of valley polarization (~37%) than MoS2.

'Sodium-scooter' delivers
Figure 2: Tellurization rate in relation to temperature and Na content. Below the dissociation temperature of MoTe2 (700 °C), IBS scientists found out that semiconducting molybdenum ditelluride (2H-MoTe2) is favored at low temperatures, and its metallic version (1T'-MoTe2) at higher temperatures. Figure 3: Cartooned version of the Na-scooter (modified from Freepik.com) Credit: IBS

More information:
Seok Joon Yun et al, Telluriding monolayer MoS2 and WS2 via alkali metal scooter, Nature Communications (2017). DOI: 10.1038/s41467-017-02238-0

Provided by Institute for Basic Science

Citation: Fast and efficient catalyst to scoot tellurium in place of sulfur, and convert 2-D MoS2 to MoTe2 at low temperature (2018, January 30) retrieved 23 September 2025 from https://sciencex.com/wire-news/278749045/fast-and-efficient-catalyst-to-scoot-tellurium-in-place-of-sulfu.html
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