Ultrathin Metal Film on Graphene for Percolation-threshold-limited Thermal Emissivity Control.

Here, we show that translucent Au/graphene hybrid films can effectively reduce thermal emission from the underlying surfaces when the deposition thickness of Au is close to the percolation threshold. The critical Au deposition thickness for an abrupt change in emissivity is reduced from 15 nm (Si substrate) to percolation-threshold-limited thickness of 8.5 nm (Graphene/Si substrate) because of the chemical inertness of graphene leading the deposited Au atoms to form a thin, crystalline layer. The effect of the graphene layer on the optical properties of the hybrid film is highlighted by a drastic increase in infrared absorptivity, whereas the visible absorptivity is marginally affected by the presence of a graphene layer. The level of thermal emission from the Au/graphene hybrid films with percolation-threshold-limited Au thickness was stable even with high background temperatures up to 300°C and mechanical strains of ∼4%. As an example of a thermal management application, we demonstrate an anti-counterfeiting device; thermal-camouflage-masked text fabricated with a Au/graphene hybrid film is discernible only using an thermographic camera. Ultrathin metal film assisted by a graphene layer will provide a facile platform for thermal management with semi-transparency, flexibility, and transferability to arbitrary surfaces. This article is protected by copyright. All rights reserved.