Outstanding properties of epitaxial graphene grown from silicon carbide substrate

Abstract

In this thesis a study of outstanding properties of epitaxial graphene on SiC were carried out involving Raman spectroscopy, AFM, UFM, XPS, Photoelectric effect and electrical resistivity. Epitaxial graphene was grown from a semi-insulating on-axis 6H (000-1) or 4H-SiC (000-1) substrate. Epitaxial growth is based on Si atoms sublimation from the SiC substrate bulk. We used the basics of epitaxial graphene growth; however small details were changed. This allowed the growth of various layers, new features and new properties. X-ray photoelectron spectroscopy XPS was used to identify the different components forming within the graphene substrate system. The graphene layer number is evidenced by XPS. Atoms percentages in the grown graphene layer were determined. Furthermore, the oxidation of the graphene layers was clearly distinguished. Atomic force microscopy AFM was carried out to study the topography response of the graphene sample. This distinguishes any morphological changes of the graphene layer. The size, orientation and regularity of the layers terraces were determined. For the first time, new features such as: island, bubbles and domes of graphene layers were identified. The nature of these features was determined using ultra force microscopy UFM . High-resolution micro-Raman (Jobin Yvon HR LabRAM) was employed to illustrate all the revealed properties. Nonetheless, it illustrates the doping, defects, disorder, number of layers and phonon-plasmon coupling of epitaxial graphene. These properties were carefully demonstrated based on local Raman mapping. The findings of these investigations indicate the formation of various types of epitaxial graphene layers. These latest could have various forms with new electrical properties. This was illustrated using a comparative study to mechanical properties of epitaxial graphene island. In fact, new charge distribution was found across these features. These findings also differs from other electrical properties found in flat graphene layers. These latest shows electroneutrality of charge distribution between graphene SiC substrate. Here, Phonons- plasmons coupling in epitaxial graphene SiC substrate system were illustrated. On other hand, epitaxial graphene properties were not limited to the graphene layers flatness. In fact, new photoresponse of epitaxial graphene under violet light was revealed. Here, photo resistance increase during to epitaxial graphene morphology.