Semimetallic Graphene for IR Sensing.

Both photothermal and photovoltaic IR detectors employ sensing materials that have an optical band gap. Different from these conventional materials, graphene has a conical band structure that imposes the zero bandgap. In this study, using the semimetallic multilayer graphene (MLG), IR detection at room temperature is realized. The relative high Seebeck coefficient, ranging 40~ 60 uV/K, comparing to that of the metal and large optical absorption in mid-IR, ranging the wavelength of 7 to 17 um, benefit the graphene for the detection of IR without an absorber, which is essential for most IR detectors because the band gap of the sensing materials is much larger than the energy of IR and the incident IR can be absorbed directly by sensing material. The developed detector with SiNx membrane shows the high responsivity and detectivity, which are 140 V/W and 5 x 108 (cm∙Hz1/2/W), respectively. In addition, the IR sensor shows a response time of 600 usec. In the room temperature operation of IR sensor array without cooling, our sensors detect IR emitted from a human body and track the movement. The availability of large-area graphene in current technology opens new applications for metallic 2D materials and a possibility for scale up.