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Molly to the Rescue

Graphene has excited technologists for years now, with its promise of high mobility, strength, and flexibility. Except for one big problem: no bandgap. So you can’t really turn off your devices.

Out of left field, then, comes something completely different at IEDM: MoS2. Deposited using CVD over a large area, a single layer configures itself as a layer of molybdenum sandwiched between two layers of sulfur. It’s flexible, it has high mobility – and it has a 1.8-V bandgap.

A team from MIT, the US Army Research Lab, and the Institute of Atomic and Molecular Sciences in Taiwan not only demonstrated the basic electrical capabilities of the material, but actually built devices, both analog (including current sources and ADCs) and digital (a depletion-mode NAND gate).

This actually competes less with small-scale circuitry and more with large-area flexible circuits, which typically utilize relatively poorly-performing materials like amorphous silicon and organics. Mobility in such devices can be less than 10 cm2/Vs. The MoS2 material achieved higher than 190 cm2/Vs, with an on-off current ratio greater than 106 and current density close to 20 µA/µm, with excellent current saturation characteristics. And the circuits worked.

For those of you with the IEDM proceedings, you can find out more in paper 4.6.

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