Electronic transport properties in nano- and micro-engineered graphene structures
24 May 2017
UAntwerpen, Campus Middelheim, A.143 - Middelheimlaan 1 - 2020 Antwerpen (route: UAntwerpen, Campus Middelheim
Organization / co-organization:
Department of Physics
PhD defence Slavisa Milovanovic - Faculty of Science, Department of Physics
Graphene shows fascinating, new properties that distinguish this material from others. Its electrons mimic relativistic particles that are rather described by the Dirac than the Schödinger equation. An interesting phenomenon that follows from this relativistic nature is the appearance of Klein tunneling. Namely, current carriers in graphene are able to overcome potential a barrier of any height and width if they approach it with zero angle of incidence making it impossible to confine electrons in graphene. An important consequence of Klein tunneling is the occurrence of snake states in the presence of a perpendicular magnetic field. The snake states appear in graphene p-n junctions when current carriers undergo a sign change of the Lorentz force.
This force bends electrons that move from one side of the junction to the other side in opposite direction and the resulting electron trajectory will resemble a snake-like trail. Thus, Klein tunneling and snake states always appear in graphene p-n junctions. The purpose of this work is to answer the question: How important is the influence of these phenomena on electrical transport in multi-terminal devices made of graphene? We try to understand them and turn them into our advantage. To do that, we use both, classical and quantum mechanical tools, to simulate physical processes in micro- and nano-sized graphene devices.
Furthermore, due to its negative refraction, graphene with a p-n junction can be used to focus electrons into a point, similarly as a lens is used to focus light. This is known as the Veselago lensing effect and the robustness of this effect is investigated in detail. In the course of this work, we study the effects of both, real and pseudo-magnetic field. The pseudo-magnetic field rises as a consequence of straining the graphene sample. It is particularly interesting because in this way we can generate pseudo-magnetic fields on the order of several hundred tesla. We investigate how the resistance is altered in the presence of strained regions of different profiles. The presented results are very important for the experimental realization of electronic devices based on graphene multi-terminal systems.