We report on the fabrication of large-area all-carbon capacitors (ACCs) composed of multilayer stacks of carbon nanomembranes as dielectrics sandwiched between two carbon-based conducting electrodes. Carbon nanomembranes (CNMs) are prepared from aromatic self-assembled monolayers of phenylthiol homologues via electron irradiation. Two types of carbon-based electrode materials, (1) trilayer graphene made by chemical vapor deposition and mechanical stacking and (2) pyrolyzed graphitic carbon made by pyrolysis of cross-linked aromatic molecules, have been employed for this study. The capacitor area is defined by the width of electrode ribbons, and the separation between two electrodes is tuned by the number of CNM layers. Working ACCs with an area of up to 1200 μm2 were successfully fabricated by a combination of bottom-up molecular self-assembly and top-down lithographic approaches. Then ACCs were characterized by Raman spectroscopy, helium ion microscopy, and impedance spectroscopy. A dielectric constant of 3.5 and an average capacitance density of 0.3 μF/cm2 were derived from the obtained capacitances. A dielectric strength of 3.2 MV/cm was determined for CNMs embedded in graphene electrodes with the interfacial capacitance being taken into account. These results show the potential of carbon nanomembranes to be used as dielectric components in next-generation environment-friendly carbon-based energy storage devices.
Keywords: carbon nanomembrane; dielectric nanocapacitors; graphene; impedance measurements; self-assembled monolayer.