Controlling electricity at the tiniest scale

Researchers at the University of California, Riverside, have uncovered how to manipulate electrical flow through crystalline silicon, a material at the heart of modern technology. The discovery could lead to smaller, faster and more efficient devices by harnessing quantum electron behaviour.

At the quantum scale, electrons behave more like waves than particles. And now, scientists have shown that the symmetrical structure of silicon molecules can be fine-tuned to create, or suppress, a phenomenon known as destructive interference. The effect can turn conductivity ‘on’ or ‘off’, functioning as a molecular-scale switch.

“We found that when tiny silicon structures are shaped with high symmetry, they can cancel out electron flow like noise-cancelling headphones,” said Tim Su, a UCR chemistry professor who led the study. “What’s exciting is that we can control it.”

Published in the Journal of the American Chemical Society, the research breaks ground in understanding how electricity moves through silicon at the smallest possible scale, atom by atom.

Chemical structure of bulk silicon, with the simplest building block of the solid highlighted in blue. Image credit: Tim Su/UCR.

The finding comes as the tech industry hits a wall in shrinking conventional silicon chips. Traditional methods rely on carving tiny circuits into silicon wafers or doping, which means adding small amounts of other elements to control how silicon conducts electricity.

These techniques have worked well for decades, but they’re approaching physical limits: you can only carve so small, and added atoms can’t fix problems caused by quantum effects.

By contrast, Su and his team used chemistry to build silicon molecules from the ground up, rather than carving them down. This ‘bottom-up’ approach gave them precise control over how the atoms were arranged and, critically, control over the way electrons move through their silicon structures.

Silicon is the second most abundant element in Earth’s crust and the workhorse of computing. But as devices shrink, unpredictable quantum effects, like electrons leaking across insulating barriers, make traditional designs harder to manage. This new study suggests that engineers might embrace, rather than fight, this quantum behaviour.

“Our work shows how molecular symmetry in silicon leads to interference effects that control how electrons move through it,” Su said. “And we can switch that interference on or off by controlling how electrodes align with our molecule.”

Electrodes along the blue path correspond to a high conducting state. With electrodes along the red paths, an insulating state was observed. Image credit: Tim Su/UCR.

While the idea of using quantum interference in electronics isn’t new, this is one of the first demonstrations of the effect in three-dimensional, diamond-like silicon — the same structure used in commercial chips.

Beyond ultra-small switches, the findings could aid in the development of thermoelectric devices that convert waste heat into electricity, or even quantum computing components built from familiar materials.

“This gives us a fundamentally new way to think about switching and charge transport,” Su said. “It’s not just a tweak. It’s a rethink of what silicon can do.”

Top image credit: iStock.com/MF3d