2D or not 2D: scientists create new, stable two-dimensional materials

2D or not 2D: scientists create new, stable two-dimensional materials

UK researchers have described a new method for the fabrication of two-dimensional (2D) materials that are unstable in ambient conditions, enabling the study of their properties.

Since the discovery of graphene in 2004 (and its array of potential applications), researchers around the world have created dozens of 2D materials. However, until now it has been impossible to use the materials because of their rapid degradation in air.

The study, led by Dr Roman Gorbachev at the University of Manchester, was published in the journal Nano Letters.

"This is an important breakthrough in the area of 2D materials research, as it allows us to dramatically increase the variety of materials that we can experiment with using our expanding 2D crystal toolbox,” explained Gorbachev.

To create the structures, the researchers assembled a bespoke glovebox to avoid contamination with oxygen and moisture. They then create the materials by cleavage, transfer, alignment and encapsulation; all carried out in an argon atmosphere. The scientists enabled this by building a fully motorised micromanipulation system that included Scientifica PatchStars. The manipulators were programmed and operated from outside the glovebox using joysticks.

The team used the fabrication method on black phosphorous (BP) and niobium diselenide (NbSe2). The improved stability allowed them to observe superconductivity in monolayer NbSe2 and the field-effect metallic conductivity of monolayer BP. The encapsulated devices could be kept in air for many weeks without showing signs of degradation.

The research should allow further study of many more atomically thin materials that can also serve as the building blocks for multilayer devices with tailored properties.

Professor Sir Andre Geim said: “The more materials we have to play with, the greater potential there is for creating applications that could revolutionize the way we live.”

Dr Roman Gorbachev is now at the new National Graphene Institute, one of the world’s leading Graphene institutes with faculty including Professor Geim and Professor Sir Kostya Novoselov (who are both named authors n the paper). They shared the 2010 Nobel Prize in Physics for their achievements with graphene.

Paper reference:

Cao Y., Mishchenko A., Yu G.L., Khestanova E., Rooney A.P., Prestat E., Kretinin A.V., Blake P., Shalom M.B. Woods C., Chapman J., Balakrishnan G., Grigorieva I.V., Novoselov K.S., Piot B.A., Potemski M., Watanabe K., Taniguchi T., Haigh S.J., Geim A.K., Gorbachev R.V. Quality heterostructures from two-dimensional crystals unstable in air by their assembly in inert atmosphere Nano Letters 15:4914-4921 (2015) doi: 10.1021/acs.nanolett.5b00648

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