Complex pattern formation in carbon thin films and multi-layer graphene through low temperature etching by catalytic combustion

This dissertation describes the development of a novel technique for complex pattern formation and shape control in carbon and graphite films which has significant importance on the properties of carbon based materials for variety of applications. Carbons are quite resistant to solvents, acids, and bases and thus cannot easily be patterned by conventional techniques. The main difficulty in current patterning technology is inability to produce large amounts of identical carbon nanostructures and precision is not possible with combination of existing lithographic and chemical methods.;This thesis demonstrates the use of catalytic combustion as a new and flexible approach to selectively etch carbon materials and focuses on controlling the etching direction by using magnetically steered catalyst particles. Catalytic combustion provides a way of using oxygen as a dry etchant by acting selectively on catalyst particles positioned by controlled metal deposition. Liquid phase catalyst deposition and carbon thin films as a model material and reaction system were used for the demonstration of this new concept. A polydimethylsiloxane stamping technique was used to transfer metal chloride solutions onto carbon thin films in the form of ordered droplet microarrays that dry to produce catalytic micropatches. The results showed that under the correct drying and reaction conditions, it is possible to convert these microdroplet arrays into well-defined micropatterned carbon films by controlled catalytic combustion. Catalyst selection, drying behavior, etchant selectivity ratio and effect of carbon substrate on the fidelity of combustion pattern were discussed.;In addition, behavior of magnetic catalyst particles on the surface of natural graphite during carbon oxidation reaction has been investigated and it has been proved that an external magnetic field could influence the mode of catalytic attack significantly. Ability to create complex, preset patterns in multi-layer graphene by catalytic channeling in the presence of external magnetic fields has been demonstrated. Graphene films were obtained from natural single graphite crystals by mechanical exfoliation. A custom resistive heat treatment device was developed to allow close proximity access for high temperature resistant powerful magnets. The mode of etching along the basal plane of graphene layers was explicitly controlled by active steering of magnetic particles and this technique has been successfully applied to create directional etched channels and predetermined complex patterns in graphene.