Impedance variation on lattice misoriented few-layer graphene via layer decoupling

We demonstrate radio frequency (RF) transmission characteristics in a layer stacked manner. Generally, as the number of graphene layers increases, the impedance is reduced and the transmission efficiency of monolayer graphene becomes better than that of chemically synthesized monolayer graphene. Depending on the stacking method, graphene may or may not be well aligned between layers; however, this characteristic affects the RF transmission. Graphene extracted from graphite is well aligned with other layers; however, synthesized graphene is randomly stacked because it is transferred and the layers are not aligned. Scattering parameters and the measured impedance shows that graphene extracted from graphite exhibits better transmission characteristics in the case of single-layer graphene, whereas synthesized graphene shows better transmission characteristics in the case of multiple-layer graphene. We calculated the change in conductivity based on the matched angle between layers of graphene and found that the conductivity was higher when the matching was less, compared to when it was well-matched. These results are also reflected in the impedance extracted from the scattering parameters. It was found that different impedance patterns are formed in single-layer graphene and in multiple layers for multi-layer graphene with stacking methods. This is because the layers are decoupled when they are randomly stacked.