Direct Growth of Graphenic Nanocarbon on Silicon Wafers for Integrated Supercapacitors

Abstract

The current state-of-the-art silicon-based miniaturised devices use a stand-alone energy source, such as Li-ion battery for continuous functioning. The silicon technology is yet to develop seamlessly integrated energy storage systems for device applications. On-wafer supercapacitor or micro-supercapacitor with planer configuration could offer a solution to meet the power demand of portable and wearable electronic devices, but their performance is limited by their low surface area and poor ion exchange. This dissertation presents a novel approach to fabricating on-silicon energy storage devices in the form of supercapacitors, enabled by cubic silicon carbide (3C-SiC) on silicon. To fabricate an integrated supercapacitor on silicon, a nickel-assisted graphitization technique is used to grow graphene on the 3C-SiC. During annealing, the 3C-SiC acts as both template and source of graphenic carbon, while, simultaneously, the nickel induces porosity on the surface by forming silicides which are subsequently removed. The surface of the SiC is made further porous by implementing a novel cyclic annealing and etching strategy, contributing to a conductive surface over an accessible and porous SiC frame. This method yields a few-layer discontinuous graphenic carbon electrode, which demonstrates double-layer capacitance with a specific energy and power density of ~0.15 Wh cm-3 and ~9.0 W cm-3, respectively, and about 88% capacitance retention over 10,000 cycles, which is representative to all the results in this study.