EAPSI:Investigating the Use of Graphene and Other 2D Materials for Use in Infrared Photodetectors

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Infrared (IR) sensors operate by absorbing incoming IR radiation and transforming that energy into heat. This heat from the absorber is then diffused through a thermoelectric material that converts the heat into electricity. The electrical signal can then be used to determine the energy of the incoming IR radiation. However, losses occurring at the junction between the absorber and the thermoelectric material cause a reduction in sensitivity and response speed which degrades performance. By using graphene or other two dimensional (2D) materials, the junction can be eliminated. This is because, despite their lack of thickness, these materials have good absorption properties and can also transform heat into electricity, making them excellent candidates for improved IR sensors. Understanding of the parameters that maximize both the absorption and the thermoelectric conversion will be essential in creating better sensors. This research will be conducted in collaboration with Professor Seong Chu Lim, a noted expert on 2D nanomaterials, at Sungkyunkwan University (SKKU) in Suwon, South Korea.Thermoelectric materials such as ZnO and SbTe are widely used in thermal applications but are transparent to incoming IR radiation due to a large band gap energy. Graphene however is a good IR absorber. However, thermoelectric IR sensors based on graphene or other 2D materials will require investigation of the parameters that influence the thermoelectric effect and the IR responsivity. To accomplish this, the researcher will focus on improving the understanding of the underlying physical phenomena so that systematic improvements of the sensor can be realized. The design of the sensor must consider both device physics and structural parameters of the sensor. If a structure can be implemented that transduces the photothermoelectric effect into an electrical output, the detection of light over a wide optical range with a constant efficiency using graphene as the absorbing material is possible. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the National Research Foundation of Korea.