University of Iowa researchers have demonstrated in two new studies how a semiconductor material can be used to create sensors that can better detect hydrogen gas and improve infrared imaging systems.

Thomas Folland, assistant professor in the Department of Physics and Astronomy, examined how microstructures made from silicon carbide can be used to develop sensors that improve safety in industrial settings and create more effective thermal imaging technologies. Silicon carbide, a heat-resistant compound of silicon and carbon, is already used in a variety of applications, such as powering electronics in electric vehicles and in renewable energy systems.

Hydrogen has been viewed by the transportation industry as a potential clean alternative to fossil fuels because its byproduct is water, instead of carbon dioxide, which contributes to warming the planet. However, there are several concerns about hydrogen’s use: The gas is more explosive than propane or methane, it can spontaneously combust when warmed, and it can be undetectable to the naked eye. Those issues mean there’s a need for sensors that can detect the gas at minute levels.

To address these challenges, Folland’s team sought to create an ultra-sensitive sensor by combining silicon carbide with a thin layer of palladium, a type of metal commonly used in electronics. When hydrogen interacts with palladium, its optical properties change slightly. Silicon carbide increases this effect, allowing the sensors to detect hydrogen in trace amounts, increasing its potential value and use in a range of industries. Compared with existing commercial sensors, the new sensor would offer the advantages of being self-calibrating, enabling real-time monitoring, and having a cost-effective design. 

In a related study, the researchers discovered that silicon carbide can improve infrared imaging, which is used in thermal cameras and sensors. In experiments, the researchers found that the material helps control how infrared light moves, known as polarization. Controlling polarization can improve contrast in thermal imaging and thus enable new types of sensors. Current polarization technologies rely on expensive, hard-to-source materials, while silicon carbide is cheaper and more readily available. 

“One of the really powerful things with both these studies is we’re turning basic research into something that is leading more into potential applications,” Folland says. 

The first study, “Harnessing phonon polaritons for dynamic and sensitive hydrogen detection in the mid-infrared,” and was published online Aug. 31 in ACS Nano, a journal of the American Chemical Society.

Study authors include Maryam Vaghefi Esfidani, from Iowa; and Guanyu Lu, Johnsu Lee, Sachin Kulkarni, Yicheng Wang, Matthew Hershey, Jamie North, Koray Aydin, and Dayne Swearer from Northwestern University. The University of Iowa Interdisciplinary Scholars program funded the research conducted at the UI. 

The second study, “Dispersion-engineered surface phonon polariton metasurfaces for tunable and efficient polarization conversion,” and was published online Aug. 11 in Nano Letters, a journal of the American Chemical Society.

Study authors include Raghunandan Iyer, Ramachandra Bangari, and Esfidani, from Iowa; and Sang Hyun Park and Tony Low from the University of Minnesota. The Office of Naval Research funded the work.