Thermostable terahertz metasurface enabled by graphene assembly film for plasmon-induced transparency

With the increasing demand on high-density integration and better performance of micro-nano optoelectronic devices, the operation temperatures are expected to significantly increase under some extreme conditions, posing a risk of degradation to metal-based micro-/nano-structured metasurfaces due to their low tolerance to high temperature. Therefore, it is urgent to find new materials with high-conductivity and excellent high-temperature resistance to replace traditional micro-nano metal structures. Herein, we have proposed and fabricated a thermally stable graphene assembly film (GAF), which is calcined at ultra-high temperature (~ 3000 ℃) during the reduction of graphite oxide (GO). Compared with micro-nano metals that usually degrade at around 550 ℃, the proposed GAF maintains a high extent of stability at an extremely high temperature up to 900 ℃. In addition, to make GAF a prime candidate to replace micro-nano metals, we have modified its fabrication process for improving its conductivity to 1.3 × 10⁶ S/m, which is quite close to metals. Thus, micro-nano optoelectronic devices could retain high efficiency even when GAF replaces the crucial micro-nano metals. To verify the thermostability of optoelectronic devices composed of GAF, we have compared the high-temperature resistance performance of two structures capable of achieving plasmon-induced transparency (PIT) at the THz region, one using micro-nano metals (Aluminum) and the other GAF. The Al metasurface displayed a near-complete loss of PIT effects after a high-temperature treatment, while GAF could remain excellent PIT properties at above 900 ℃, thus enable to fulfil its optimum performance. Overall, the proposed thermostable metasurface provides new pathway for the construction of thermostable optoelectronic devices that can operate under ultra-high temperature scenario.