Electric Transport in Hybrid Carbon Nanotube-Graphene Devices

Abstract

Two remarkable properties exhibited by graphene electrons are their pseudo-relativistic behavior and their ballistic motion that mimics the propagation of electromagnetic waves in a refractive medium. Despite heavy investigation, limitations of existing fabrication and measurement techniques have prevented certain aspects of these phenomena from being thoroughly explored or realized. Two in particular are Landau level collapse and the single-mode waveguide. Observing these phenomena requires a sharp modulation of the potential landscape of graphene as well as a probe to detect the resulting local electronic behavior. Incorporating a carbon nanotube into a graphene heterostructure allows us to do both simultaneously. This thesis describes the fabrication procedure of the hybrid carbon nanotube-graphene device and explains its operational principle. We demonstrate the carbon nanotube can act as a local probe and use it to measure the electronic properties of graphene. With an external magnetic field and with the carbon nanotube as an electric field generator, we perform a detailed study of Landau level collapse and draw connections to relativistic dynamics. When the potential well in graphene due to the carbon nanotube is made deep enough, we observe a clear signature of a single guided mode. Lastly, we present preliminary results on Coulomb drag between a carbon nanotube and graphene, and discuss the next steps toward reaching the goal of observing hydrodynamic behavior in graphene.