Graphene is winning fans, awards and application possibilities seemingly daily. But the elephant in the room, if you will, when discussing graphene, is the problem of it lacking a band gap.

Huge strides have been made in overcoming that shortcoming, but let’s just say that not having a band gap in its nature is more than a small liability for graphene in electronic applications.

Into this mix, researchers at Ecole Polytechnique Federale de Lausanne’s (EPFL) Laboratory of Nanoscale Electronics and Structures (LANES) had their research published this week in the journal Nature Nanotechnology that offers the humble and abundant mineral molybdenite (MoS2) as an attractive alternative to silicon as a two-dimensional material (like graphene is) for replacing the three-dimensional silicon in transistors.

"It's a two-dimensional material, very thin and easy to use in nanotechnology. It has real potential in the fabrication of very small transistors, light-emitting diodes (LEDs) and solar cells," says EPFL Professor Andras Kis in an article that reports on the research.

The big advantage it has over graphene in the search for a replacement to silicon: it has a band gap. And when it comes to being better than silicon, the advantages are impressive.

"In a 0.65-nanometer-thick sheet of MoS2, the electrons can move around as easily as in a 2-nanometer-thick sheet of silicon," explains Kis. "But it's not currently possible to fabricate a sheet of silicon as thin as a monolayer sheet of MoS2."

The researchers also report that transistors made from molybdenite will use 100,000 times less energy in a standby state than traditional silicon transistors.

As explained in the Nature abstract, molybdenite does not have to stand in competition with graphene, but could complement graphene “in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.”

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3D-Stacked CMOS Takes Moore’s Law to New Heights

When transistors can’t get any smaller, the only direction is up

10 min read
An image of stacked squares with yellow flat bars through them.
Emily Cooper
Green

Perhaps the most far-reaching technological achievement over the last 50 years has been the steady march toward ever smaller transistors, fitting them more tightly together, and reducing their power consumption. And yet, ever since the two of us started our careers at Intel more than 20 years ago, we’ve been hearing the alarms that the descent into the infinitesimal was about to end. Yet year after year, brilliant new innovations continue to propel the semiconductor industry further.

Along this journey, we engineers had to change the transistor’s architecture as we continued to scale down area and power consumption while boosting performance. The “planar” transistor designs that took us through the last half of the 20th century gave way to 3D fin-shaped devices by the first half of the 2010s. Now, these too have an end date in sight, with a new gate-all-around (GAA) structure rolling into production soon. But we have to look even further ahead because our ability to scale down even this new transistor architecture, which we call RibbonFET, has its limits.

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