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Layered transition metal dichalcogenides or TMDCs -- materials composed of metal nanolayers sandwiched between two other layers of chalcogens -- have become extremely attractive to the research community due to their ability to exfoliate into 2D single layers. Similar to graphene, they not only retain some of the unique properties of the bulk material, but also demonstrate direct-gap semiconducting behavior, excellent electrocatalytic activity and unique quantum phenomena such as charge density waves (CDW).

Generating complex multi-principle element TMDCs essential for the future development of new generations of quantum, electronic, and energy conversion materials is difficult.

"It is relatively simple to make a binary material from one type of metal and one type of chalcogen," said Ames Laboratory Senior Scientist Viktor Balema. "Once you try to add more metals or chalcogens to the reactants, combining them into a uniform structure becomes challenging. It was even believed that alloying of two or more different binary TMDCs in one single-phase material is absolutely impossible."

To overcome this obstacle, postdoctoral research associate Ihor Hlova used ball-milling and subsequent reactive fusion to combine such TMDCs as MoS2, WSe2, WS2, TaS2 and NbSe2. Ball-milling is a mechanochemical process capable of exfoliating layered materials into single- or few-layer-nanosheets that can further restore their multi-layered arrangements by restacking.

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Category: Science