Cabosart, Damien
[UCL]
In the fields of condensed matter physics and electronics, the advent of new types of materials with unconventional charge carrier dynamics first gives possibilities to explore peculiar physical phenomena, which can then open novel routes for the design of electronic devices. It is the case of graphene, a two-dimensional carbon crystal where charge carriers behave like massless relativistic particles. To benefit from the outstanding properties potentially offered by such a material, the first step is to understand how charge carriers propagate through graphene devices in order to control their motion inside the considered structures. In this thesis, we present experimental results on the electronic transport inside two types of graphene-based devices : (I) nitrogen-incorporated graphene Hall bars and (II) graphene quantum ring (QR) interferometers. A particular attention was brought to the investigation of coherent effects, involving charge carrier interferences. In addition, a scanning probe technique, called scanning gate microscopy (SGM), was used to image and control charge carrier dynamics inside mesoscopic graphene QRs at the local nm-scale. In nitrogen-incorporated graphene, our results evidence the substantial influence of the disorder induced by the presence of nitrogen atoms in the graphene lattice. We then directly observe in real space the effect of disorder in different transport regimes in SGM images of QRs. Beside the influence of disorder, SGM mapping of the charge carrier wave functions inside graphene QRs reveals the formation of scarlike features reminiscent of semi-classical periodic orbits scarring the local density of states along the QRs’ arms. Patterns imaged in SGM are found to be recurrent when varying the charge carrier energy, consistent with theoretical predictions for relativistic quantum scars.
Bibliographic reference |
Cabosart, Damien. Coherent transport and scanning gate microscopy in graphene devices. Prom. : Hackens, Benoit |
Permanent URL |
http://hdl.handle.net/2078.1/182852 |