Few-Layer Transition Metal Chloride Graphene Intercalation Compounds

Few-layer transition metal chloride graphene intercalation compounds have
been fabricated by the mechanical exfoliation of graphite intercalation compounds (GICs) containing CoCl_2, NiCl_2, CuCl2, MnCl_2 and FeCl_3. The number of graphene layers and the distribution of the intercalate in the
few-layer graphene intercalation compounds (FLGICs) have been characterised using the optical contrast of the FLGICs against the SiO_2 substrate and the G-peak of the Raman spectrum. FLGICs containing a single intercalate layer surrounded by two graphene layers have been fabricated and characterised, which are an ideal system to study 2D magnetic phase transitions. Atomic force microscopy (AFM), electrostatic force microscopy (EFM), Kelvin probe force microscopy (KPFM) and spatial maps of the Raman spectrum have revealed the intercalate layers in FLGICs form domains several microns across due to deintercalation from mechanical exfoliation. Once exfoliated, the domain structure of FLGICs remains stable for many months. Electronic transport and Raman spectroscopy measurements reveal the graphene layers in FLGICs to be highly p-doped with charge densities of up to n = 8 x 10^13 cm^-2, making them suitable to be used as transparent conductors in future electronic devices.