Investigation of Liquid Metal Ohmic Contacts for Graphene Photonic Devices

We demonstrate the first contact resistance measurements of graphene–galinstan (g-g) ohmic contacts in an effort to improve the performance of graphene photonic devices. The nobility of carbon materials provide an interesting graphene sensor application to explore an oxidation free liquid metal - semimetal interface that can be used to lower contact resistance at source/drain terminals of a standard graphene phototransistor. Our methods utilize photopolymerization of the reactive monomer Trimethlylolpropane Triacrylate (TMPTA) in order to fabricate micro structures necessary to overlay liquid metal contacts on graphene. With the use of an industry standard transfer length method (TLM), a contact resistance of −124±28Ω was measured at both standard temperature and pressure. The results from our study suggest that liquid metals such as galinstan are comparable alternatives to rigid semiconductor interfaces and demonstrates interesting boundary characteristics that may lead to heavy chemical doping and associated low resistance contacts that are required to increase sensitivity in graphene photonic devices.