Reduction degree regulated room-temperature terahertz direct detection based on fully suspended and low-temperature thermally reduced graphene oxides

Abstract A series of fully-suspended reduced graphene oxide (RGO) room-temperature THz detectors were fabricated based on low-temperature (from 100 to 350 °C) thermally-reduced free-standing graphene oxide (GO) thin films. The suspended configuration results in a four-fold increase in responsivity and at least one order of magnitude increase in response speed compared to the substrate-supported detector. More importantly, the responsivity can be adjusted over a wide range from 10−2–102 mA W−1 and simultaneously the response speed can be adjusted on the order of tens of milliseconds by only tuning the reduction temperature of GO namely the reduction degree of GO. The regulation mechanism was revealed at the molecular level, i. e., the content of C=O functional group and the O/C ratio inside RGO, which are vary with the reduction degree of GO, are closely related to THz absorbance and electrical conductivity of RGO thin films, respectively. The experimental results demonstrated that the as high as possible content of C=O functional group and simultaneously a moderate O/C ratio can achieve optimal synergy between the THz absorption and electrical conductivity of the RGO thin films, thereby achieving an optimal THz detection performance.