1 Department of Micro- and Nanotechnology, Technical University of Denmark2 Nanointegration, Department of Micro- and Nanotechnology, Technical University of Denmark3 Center for Nanostructured Graphene, Center, Technical University of Denmark
Engineering of graphene for modifying electrical properties, such as opening an electronic band gap, has been shown both theoretically and experimentally by creating periodic holes in the graphene sheet, however at the price of lower carrier mobility. Such holes can be made with special fabrication techniques, such as colloidal lithography or block copolymers lithography, which covers the entire sample. This project presents graphene devices with periodic holes fabricated by electron beam lithography. Only partial coverage of holes are fabricated by making from one to many rows of holes perpendicular to the current direction. The results show a decrease in carrier mobility with increasing number of rows, but does not indicate a band gap opening with holes sizes of 50 nm and a pitch of 100 nm, which suggests that smaller holes and pitch are necessary for creating band gap in graphene. Electrical characterization of graphene and other nanostructures usually involves lithographic processing which can alter or damage fragile materials, and metal electrodes are permanently placed to the sample. This project presents a fast method for electrical characterization for graphene and other nanostructures by the use of micro four-point probes. My contribution to knowledge includes characterization of graphene using micro four-point probes, which proves to be a fast and reliable method for electrical and mechanical characterization. The micro-four point probe technique is shown to apply to other fragile nanostructures, such as nanograss and silver nanowires. Furthermore, antidot lattice of dierent sizes are made in graphene, to investigating the dependence of number of holes needed for modifying the electronic properties of graphene.