(191e) Dense Semiconducting Nanowire Arrays Grown Directly On Graphene

Semiconducting nanowires have been demonstrated as promising in a number of devices due to novel properties which are intrinsic to their nanoscale. Silicon nanowires are promising for lithium battery electrodes, where the nanowire geometry allows for relaxation of mechanical stress associated with lithium insertion. Silicon nanowires are also attractive for thin film solar cells, where the nanowire geometry results in enhanced broadband absorption and enables thinner cells with increased efficiency. As well as silicon, the properties of silicon carbide nanowires including large specific surface area and high aspect ratio lend them to application as supercapacitor electrodes and field emitters respectively. Typically these materials are grown via vapor deposition techniques at high temperatures in harsh chemical environments. These growth conditions require refractory, rigid substrates. Yet in order to integrate these materials into devices, they must be accurately transferred and electrically contacted on the array scale. Previous efforts in the transfer step have utilized the Langmuir-Blodgett technique or polymer stamping. The arrays are then electrically contacted through metal evaporation methods. Here we demonstrate an improvement over these previous techniques by growing the nanowires directly on a conductive, flexible, and mechanically robust graphene. The arrays of wires may then be transferred in a facile manner while maintaining good electrical contact throughout the array. The wire-graphene hybrids are structurally characterized via Raman spectroscopy, scanning electron microscopy and x-ray diffraction confirming their chemical identity and crystalline nature. As well, Raman spectroscopy is used to confirm that high quality graphene is maintained during the nanowire growth process. Transfer of the hybrids is demonstrated to a number of arbitrary substrates while maintaining electrical contact. Silicon carbide nanowire – graphene hybrids are also applied as a supercapacitor electrodes with performance indicating good electrical contact throughout the array. Lifetime cycling studies on these electrodes indicate that the hybrid is a robust material with over 95% capacitance retention after 10,000 charge discharge cycles in aqueous electrolyte.