Graphene nanosheet as ultrathin barrier

Graphene, a two-dimensional layer of sp²-bonded carbon atoms in a closely packed hexagonal honeycomb lattice, has been attracting lots of attention due to its unique properties, including atomic-level thickness [1], high optical transmittance in the visible regime [2], high carrier mobility (approaching 120,000 cm²/V/s for suspended graphene at low temperature) [3], high thermal conductivity (~6000 W/m·K) [3,4], ultrahigh mechanical strength (42 N/m) [5], and high impermeability to gas and liquid [6]. Recent advances in the controllable fabrication of large-area and high-quality graphene [7-9] have brought it close to practical application in various fields, for example, ultra-high-frequency devices [10], transparent electrodes [11], biosensors [12], gas sensors [13], oxidation/corrosion barriers [14], and solar cells [15].