Graphene and Silicon Materials for Quantum Computing - Anisotropic etching in graphene and high mobility SiMOSFETs with thin oxides

Quantum computing has the highest demand on device quality in order to achieve long coherence times. Therefore, this thesis investigates the two materials graphene and silicon for their particular use in quantum computing applications.
Graphene nanoribbons (GNRs) are a very promising playground for novel states of matter like Majorana fermions, for spin filtering or magnetic ordering. The creation of such states depends on the edge termination of the GNRs which can be produced by using a remote hydrogen or remote nitrogen plasma respectively. Here, we report the successful use of a remote hydrogen plasma which creates etch pits with zigzag terminated edges. This demonstrates the viability of a GNR fabrication process for spin-filtering applications in graphene systems. A remote nitrogen plasma has also been investigated, however, we were not able to find the remote nitrogen regime where anisotropic etching occurs.
Second, silicon is already widely used as a promising candidate for spin qubit applications. The goal of the experiments conducted in this thesis was to investigate the quality of a device fabricated in a fully CMOS compatible process. This has been done by measuring the mobility of the electric charge carriers and by analysing the top gate material influence on the mobility. We report a record mobility of 17.5 x 10^3 cm^2/Vs which, in combination with other extracted parameters, indicates a high quality interface, opening new avenues for high quality quantum dot applications.