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Plasmonics Used to Dope Graphene

Research promises the creation of instantaneous circuitry simply by applying light to graphene

2 min read
Plasmonics Used to Dope Graphene

The big push in graphene research for electronics has been overcoming its lack of an inherent band gap.  But silicon has another leg up on graphene when it comes to electronics applications: it can comparatively easily be p- and n-doped (positive and negative).

While there have been a number of approaches taken for doping graphene, researchers at Rice University believe that the idea of plasmon-induced doping of graphene could be ideal for this purpose.

The research (“Plasmon-Induced Doping of Graphene”), which was published in the journal ACS Nano, looks to use plasomonics,which exploits the fact that “photons striking small, metallic structures can create plasmons, which are oscillations of electron density in the metal.”

The Rice team placed nanoscale plasmoic antennas—dubbed nonamers—on the graphene to manipulate light in such a way that they inject electrons into the graphene, changing its conductivity. The nonamers tooks the form of eight nanoscale gold discs that encircled one large gold disc, and were placed on the graphene with electron beam lithography.

When the graphene and nonamers are exposed to light, the incident light is converted into hot electrons that transform those portions of the graphene where the nonamers are located from a conductor to an n-doped semiconductor.

“Quantum dot and plasmonic nanoparticle antennas can be tuned to respond to pretty much any color in the visible spectrum,” says Rice professor Peter Nordlander, one of the authors of the paper, in the university's press release about the research. “We can even tune them to different polarization states, or the shape of a wavefront."

Nordlander adds: “That’s the magic of plasmonics. We can tune the plasmon resonance any way we want. In this case, we decided to do it at 825 nanometers because that is in the middle of the spectral range of our available light sources. We wanted to know that we could send light at different colors and see no effect, and at that particular color see a big effect.”

While the possibility of a process that simply uses light for doping graphene seems pretty amazing, the researchers are looking ahead to a day when a flashlight in a particular pattern would replace a key for unlocking a door by triggering the circuitry of the lock to open it. “Opening a lock becomes a direct event because we are sending the right lights toward the substrate and creating the integrated circuits. It will only answer to my call,” Norlander suggests in the release.

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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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