LSU-Led Research Team Shows Alloys Could Excel at Detecting Infrared Light

Making the news:  K. McPeak, P. Sprunger, and O. Kizilkaya

May 11, 2020

BATON ROUGE, LA – A group of researchers from LSU, Argonne National Laboratory and Drexel University have discovered an alloy that has practical application in the ultrafast detection of near-infrared light, which is important to the military for missile defense systems and night vision goggles.

The research was published in the latest issue of Advanced Materials in a paper titled, “Noble-Transition Alloy Excels at Hot-Carrier Generation in the Near Infrared.”

The project was led by LSU Chemical Engineering Assistant Professor Kevin McPeak and his graduate student Sara Stofela in collaboration with LSU Chemical Engineering Professor William Shelton, LSU Chemical Engineering graduate students Tiago Leite and Daniel Willis, LSU Physics Professor Phillip Sprunger, LSU Center for Advanced Microstructures & Devices Professor Orhan Kizilkaya, Benjamin Diroll with Argonne National Laboratory’s Center for Nanoscale Materials, and Mohammad Taheri and Professor Jason Baxter with Drexel University’s Department of Chemical and Biological Engineering.

The group’s work, which took place over four years, focused on developing a material that excels at generating hot carriers when excited with near-infrared light.

Near-infrared light cannot be seen by the human eye, making it useful for the military in reconnaissance missions. Hot carriers are electrons and holes, which are above and below, respectively, the equilibrium energy of the system. Since these carriers are above the equilibrium energy of the system, they can be used to drive an electrical circuit.

The problem, however, is finding a material that will offer both hot-carrier generation and a sufficient carrier lifetime so that the electrons and holes can be collected from the metal. Single-element metals struggle to do this well. There is, however, as the team discovered, an alloy that fits the bill.

“We explored an alloy of gold and palladium in this paper,” McPeak said. “Au (or gold) has been heavily studied for the generation of hot carriers by other groups, especially in under visible light. Pd (or palladium) can generate a lot of carriers in the near-infrared but they decay very rapidly because the carriers scatter off each other. The hot carriers decay so fast in Pd that they can’t be extracted quick enough to drive an electric circuit.

“We show that by alloying Au and Pd we can both extend the lifetime of the carriers in Pd and increase the number of carriers from Au. These alloy materials have practical applications in the ultrafast detection of near-infrared light, which is important to the military for intelligence, surveillance, and reconnaissance systems.” (College of Engineering)

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