Graphene-based IR Detector using Photo-thermoelectric Effect

Abstract

Graphene has widely been used in electronic and photonic devices due to its unique properties such as fast electron mobility and broadband absorption. Especially, the electronic heat capacity of single layer graphene is much lower than in bulk materials, resulting in a large and rapid change in temperature for the same absorbed energy. Therefore, graphene is a good material for making photo-thermoelectric detectors that require electromagnetic radiation absorption and strong thermal gradients at room temperature. Photo-excited carriers in graphene thermalize rapidly due to strong electron-electron interaction, but slowly lose energy in the lattice. Thus, it is possible to have a faster response speed than a conventional uncooled infrared detector that measures the change of thermal resistance according to temperature. In this research, I fabricated a graphene based infrared detector operating at room temperature. Graphene was used as a light absorber and the common metals and thermoelectric materials were judiciously chosen at the two ends of the graphene channel for desired thermoelectric effect. To verify the performance of the detector, the response voltage was measured. The device made of two thermoelectric materials, whose Seebeck coefficients are significantly distinct, had a higher response voltage. A sample made of the same material at the channel ends was also tested to differentiate photoelectric effect from photo-thermoelectric effect in a sample of two end materials.