Fabrication and characterization of graphene nanodevices

Abstract

[ES]In this Thesis our results on the fabrication of graphene nanodevices and their magnetotransport properties will be shown. In particular, we have fabricated several graphene nanodevices exploring the routes to field effec transistors using different approaches and fundamental physics research using Hall bars, Corbino rings and more exotic geometries. We have studied the quantum Hall effct in several graphene nanodevices: bilayer graphene and trilayer graphene, studying the transport regimes when unwanted charged dopants are present in the device. We extended our studies on the quantum Hall effect and characterized the plateauplateau quantum phase transition in a high mobility bilayer graphene device. Our results on the quantum phase transitions showed to be compatible with a percolation scenario in which the critical exponent of such transition is y=4/3. We have also studied the low field regime in a monolayer graphene device and a bilayer graphene device. For the monolayer graphene device, the trigonal warping is manifested in the destruction of the weak antilocalization. The bilayer graphene sample showed different transport regimes (from insulator like to metallic like) driven by the density. Furthermore, a change in the temperature resulted in ballistic transport for higher densities. Finally, the interplay between the graphene surface and a thin film of tantalum has been studied. We have observed a clear difference between the charge transfer from 3D porous carbon and tantalum and that from 3D porous graphene and tantalum, manifested in a modification of the superconducting properties of thin films of tantalum.