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Molybdenum disulfide shows silicon-like properties

Posted: 18 Feb 2015 ?? ?Print Version ?Bookmark and Share

Keywords:University of Pennsylvania? silicon? graphene? molybdenum disulfide?

As a result of its extremely high conductivity and unmatched thinness, graphene, a single-atom-thick lattice of carbon atoms, is often flaunted as a replacement for silicon in electronic devices. However, a recent study shows that graphene is not the only 2D material with such properties.

University of Pennsylvania researchers have made an advance in manufacturing one such material, molybdenum disulfide. By growing flakes of the material around "seeds" of molybdenum oxide, they have made it easier to control the size, thickness and location of the material.

Unlike graphene, molybdenum disulfide has an energy band gap, meaning its conductivity can be turned on and off. Such a trait is critical for semiconductor devices used in computing. Another difference is that molybdenum disulfide emits light, meaning it could be used in applications such as LEDs, self-reporting sensors and optoelectronics.

Molybdenum disulfide

"Seeding" the growth of molybdenum disulfide flakes gave the researches enough control over their location to spell a message.

The study was led by A.T. Charlie Johnson, professor in the Department of Physics & Astronomy in Penn's School of Arts & Sciences, and includes members of his lab, Gang Hee Han, Nicholas Kybert, Carl Naylor and Jinglei Ping. Also contributing to the study was Ritesh Agarwal, professor of materials science and engineering in Penn's School of Engineering and Applied Science; members of his lab, Bumsu Lee and Joohee Park; and Jisoo Kang, a master's student in Penn's nanotechnology programme. They collaborated with researchers from South Korea's Sungkyunkwan University, Si Young Lee and Young Hee Lee.

Their study was published in the journal Nature Communications.

"Everything we do with regular electronics we'd like to be able to do with 2D materials," Johnson said. "Graphene has one set of properties that make it very attractive for electronics, but it lacks this critical property, being able to turn on and off. Molybedenum disulfide gives you that."

A.T. Charlie Johnson

A.T. Charlie Johnson

Graphene's ultra-high conductivity means that it can move electrons more quickly than any known material, but that is not the only quality that matters for electronics. For the transistors that form the basis for modern computing technology, being able to stop the flow of electrons is also critical.

"Molybedenum disulfide is not as conductive as graphene," Naylor said, "but it has a very high on/off ratio. We need 1's and 0's to do computation; graphene can only give us 1's and .5's."

Other research groups have been able to make small flakes of molybdenum disulfide the same way graphene was first made, by exfoliating it, or peeling off atomically thin layers from the bulk material. More recently, other researchers have adopted another technique from graphene manufacture, chemical vapour deposition, where the molybdenum and sulphur are heated into gasses and left to settle and crystallise on a substrate.

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