A UCR electrical and computer engineering professor has been awarded a $400,000 grant from the National Science Foundation to illuminate how light turns into electricity inside of next-generation photodetector devices.
Ming Liu, an associate professor in UCR’s Marlan and Rosemary Bourns College of Engineering, received the grant to develop a new three-dimensional imaging method capable of revealing electrical hotspots at the nanometer scale—thousands of times thinner than a human hair.
The project aims to decode a complex interaction inside ultrasmall photodetectors, devices used in everything from smartphones to fiber-optic networks. These detectors are critical in a world that increasingly depends on fast and efficient sensing and communication. But as the devices shrink, so too does engineers’ ability to see what’s really going on inside.
“Right now, engineers often have to guess which part of a tiny device is doing the work,” Liu said. “Our goal is to provide a clear map—to separate heat-driven electrical signals from light-driven signals—so we can design faster, cleaner, and more efficient detectors for real-world use.”
At the core of the problem are two competing physical effects. One is the photovoltaic (PV) effect—the principle that powers solar panels—in which light directly creates a current by dislodging electrons. The other, lesser known, is the photothermoelectric (PTE) effect, in which light heats the electrons, and that heat drives them to cooler areas, producing current.
In nanoscale devices, these effects intertwine in ways scientists couldn’t previously measure. Liu’s team aims to change that by refining an approach known as 3D Near-Field Scanning Photocurrent Microscopy. Using this technique, light is funneled through the needle-sharp tip of an atomic-force microscope to trace photocurrent generation down to sub-5-nanometer precision—well below the limits of visible light.
“It’s like having a nanoscale traffic report for electricity,” Liu said. “We’re watching how light and heat move charges through intricate materials and tiny features.”
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