Structural and Electronic Properties of Graphene on 4H- and 3C-SiC

Abstract

Je dédie cette thèse pour ceux qui sont très loin de moi et très prochesà mon coeur:Pour celle qui vient de l'île des rêves et qui a changè ma vie au plus beau rêve.Pour celle que je dois ma vie. Pour ma famille.Pour ceux qui ne perdent jamais la foi en l'humanité. v ABSTRACTGraphene is a one-atom-tick carbon layer arranged in a honeycomb lattice. Graphene was first experimentally demonstrated by Andre Geim and Konstantin Novoselov in 2004 using mechanical exfoliation of highly oriented pyrolytic graphite (exfoliated graphene flakes), for which they received the Nobel Prize in Physics in 2010. Exfoliated graphene flakes show outstanding electronic properties, e.g., very high free charge carrier mobility parameters and ballistic transport at room temperature. This makes graphene a suitable material for next generation radio-frequency and terahertz electronic devices. Such applications require fabrication methods of large-area graphene compatible with electronic industry. Graphene grown by sublimation on silicon carbide (SiC) offers a viable route towards production of large-area, electronic-grade material on semi-insulating substrate without the need of transfer. Despite the intense investigations in the field, uniform wafer-scale graphene with very high-quality that matches the properties of exfoliated graphene has not been achieved yet. The key point is to identify and control how the substrate affects graphene uniformity, thickness, layer stacking, structural and electronic properties. Of particular interest is to understand the effects of SiC surface polarity and polytype on graphene properties in order to achieve large-area material with tailored properties for electronic applications. The main objectives of this thesis are to address these issues by investigating the structural and electronic properties of epitaxial graphene grown on 4H-SiC and 3C-SiC substrates with different surface polarities.The first part of the thesis includes a general description of the properties of graphene, bilayer graphene and graphite. Then, the properties of epitaxial graphene on SiC by sublimation are detailed. The experimental techniques used to characterize graphene are described. A summary of all papers and contribution to the field is presented at the end of Part I. Part II consists of seven papers.Paper I reports on the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC(000 − 1) with surface defects. We have shown that the average number of graphene layers, the size of the domains with uniform thickness and the crystallite size increase with the increase of temperature. This improved graphene quality is attributed to an enhanced sublimation of Si from the SiC and to the elimination of SiC surface defects by surface restructuring during the sublimation growth. Central result of the paper is the transition from decoupled to Bernal stacked graphene layers with the increase in growth temperature, which is explained by a competition between growth mechanisms. We also determin...