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Researchers develop one-way street for electrons



Researchers develop one-way street for electrons

In an ultra-small geometry under the right conditions, electrons can be treated as particles bouncing off a wall. If the electrons are in a wire and symmetry is broken, the electrons can preferably be funneled in one direction and blocked in the other, creating an electric diode. Credit: J. Custer

Researchers at the University of North Carolina at Chapel Hill created a one-way street for electrons that can unlock the ability for devices to process ultra-high-speed wireless data while harvesting energy for power. The researchers did this by forming silicon on a microscopic scale to create a funnel, or “barrier”

;, for electrons.

This method overcomes the speed restrictions of previous technologies by removing interfaces that tend to slow down devices. “This work is exciting because it can enable a future where things like low-power smartwatches are wirelessly loaded from the data they already get without ever having to leave a person’s wrist,” said James Custer Jr., a graduate student at UNC-Chapel Hill’s College of Arts & Sciences.

The results were published on April 10 in the journal Science. Custer is the lead author. He worked with collaborators at Duke and Vanderbilt University.

Electrons have electrical current, and they do not usually care about the shape of the wire in which the current flows. But when things get very small, the shape begins to become important. The funnels here are ultra-small, more than a million times smaller than a typical electrical line. As a result, the electrons inside appear like billiard balls – bouncing freely from the surfaces. The asymmetric funnel causes the electrons to bounce preferably in one direction. In fact, the electrons are forced to follow a one-way street.

Under a DC (DC) voltage, the funnel makes it easier for current to flow in a forward direction than the reverse direction, creating an electric diode. When AC (AC) is applied, the structure still only allows current to flow in one direction, behaves like a barrier and causes electrons to build up on one side. This process is like a socket wrench, which locks forces to produce physical movement in a single direction.

The work has shown that these electron blocks create “geometric diodes” that work at room temperature and can unlock outstanding capabilities in the illusive terahertz regime.

“Electric diodes are a basic component of electronics, and our results suggest that there may be a completely different paradigm for the design of diodes that work at very high frequencies,” said James Cahoon, associate professor of chemistry. Cahoon is the corresponding author and led the study’s research group. “The results are possible because we grow the structures from the bottom up using a synthetic process that yields geometrically accurate, single-crystalline materials.”

The electron barrier is created by a process previously developed in the Cahoon group called ENGRAVE, which stands for “Coded Nanowire Growth and Appearance through VLS and Etching.” ENGRAVE uses a vapor-liquid process to chemically grow silicon single crystal cylinders, called nanowires, with precisely defined geometry.

“Much of the work in this area has previously been done with expensive materials at cryogenic temperatures, but our work highlights that geometric diodes made with relatively cheap silicon can work at room temperature, which even surprised us at first,” Custer said. “We hope our results are of great interest to geometric diodes.”

Diodes are the backbone of all technology; they allow computers to process data by encoding signals such as 1s and 0s. Traditionally, diodes require interfaces between materials, such as between n-type and p-type semiconductors or between semiconductors and metals. In contrast, geometric diodes are made of a single material and simply use shape to direct charges preferably in one direction.

With continued development, nanowire electron rafters promise to pave a high-speed, one-way path to new technology.


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More information:
“Ratcheting quasi-ballistic electrons in silicon diodes at room temperature” Science (2020). science.sciencemag.org/cgi/doi … 1126 / science.aay8663

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University of North Carolina at Chapel Hill




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Scientists develop a direction for electrons (2020, April 9)
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