Could Molybdenite Become a Replacement for Silicon in Electronics?



Could Molybdenite Become a Replacement for Silicon in Electronics?
While graphene is touted as a replacement for silicon in electronics due to its extremely high conductivity, it is not the only material that could play a role.
Technology Briefing

Transcript


While graphene is the material most often touted as a replacement for silicon in electronic devices due to its extremely high conductivity and unbeatable thinness, it is not the only two-dimensional material that could play such a role.

One such material is molybdenum disulphide, more commonly referred to as "molybdenite." Unlike graphene, molybdenum disulphide 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 disulphide emits light, meaning it could be used in applications like LEDs, self-reporting sensors, and optoelectronics. Researchers would like to be able to do with two-dimensional materials everything they can with regular electronics.

Graphene has one set of properties that make it very attractive for electronics: Its 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, and graphene lacks the critical property of being able to turn on and off.

Molybdenum disulphide is not as conductive as grapheme, but it has a very high on/off ratio. As with graphene, a revolution based on molybdenite awaits the development of a process for cheaply and reliably manufacturing it.

As recently explained in the journal Nature Communications, researchers at the University of Pennsylvania have now made it easier to control the size, thickness, and location of this material by growing flakes of the molybdenite around "seeds" of molybdenum oxide.

Other research groups have been able to make small flakes of molybdenum disulphide 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 vapor deposition, where the molybdenum and sulfur are heated into gases and left to settle and crystalize on a substrate.

The Penn team's advance was in developing a way to control where the flakes form in the chemical vapor deposition method, by "seeding" the substrate with a precursor. Under the right conditions, those seeds react with sulfur, and flakes of molybdenum disulphide begin to grow.

Because the flakes grow where they are wanted, the devices can be made more easily. All the other parts of the transistors are in a separate layer that is snapped down on top of the flakes, making dozens and potentially even hundreds of devices at once.


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