Conductive three-layer-stacked polycrystalline graphene intercalated with FeCl3

Graphene has attracted attention as a new transparent conductive film (TCF) because of its transparency, stability, strength, and versatility. However, it has a higher resistance than conventional TCFs. Recently, vapor transport intercalation with doping effect materials has been investigated to reduce the resistivity of graphene. Studies have revealed a correlation between the stacking structure and the intercalation efficiency, which favors smaller interactions between the graphene layers. In this study, polycrystalline graphene, which consists of small domains, grown by chemical vapor deposition is stacked in three layers using a layer-by-layer method, and the graphene layers are intentionally randomly stacked to suppress the interlayer interactions. Intercalation of FeCl₃, which has p-type doping effects, into randomly stacked three-layer graphene (3LG) significantly reduces the sheet resistance (Rs) of 3LG from 500 to 41 Ω/sq. Interestingly, Raman mapping of the G peak shift of FeCl₃ intercalated into randomly stacked 3LG indicates that in-plane intercalation proceeds homogeneously, even though strong interlayer interactions such as AB stacking are observed in some parts of 3LG. This study reveals that a randomly stacked polycrystalline graphene layer is advantageous for intercalation.