Scientists at the University of Maryland’s Center for Nanophysics and Advanced Materials have created a sensitive infrared light detector that can be used in applications ranging from airport body scanners to chemical weapons detection.
The hot electron bolometer uses bilayer graphene carbon sheets with the thickness of two atoms. The unique properties of the graphene allow the bolometer to be sensitive to a broad range of light energies, including submillimeter waves, terahertz frequencies, visible light and infrared light. The bolometer works by measuring changes in resistance resulting from heating electrons as they absorb light.
Because bolometers require temperature dependence and graphene has resistance that is practically independent of temperature, the researchers took advantage of a small band gap generated when the bilayer graphene is exposed to an electric field. The electric field causes the graphene to become temperature dependent and is small enough to maintain an ability to absorb infrared photons with low energy.
The researchers determined that when their bilayer graphene operated at five degrees Kelvin, the bolometer had comparable sensitivity to existing bolometers. The major difference, however, was that the graphene bolometer was more than one thousand times faster than existing bolometers. A faster bolometer could lead to faster chemical weapon detection in the field for first responders.
Researchers are working on getting around several issues that graphene presents, though they are confident that the material can work very effectively as photo-detecting material.