Study of the electronic and atomic structure of functionalized nanoporous graphene via on-surface chemical synthesis

Abstract

Complex and functionalized nanostructures based on graphene (Gr), such as doped Gr-nanoribbons, Gr-nanoflakes, and 2D porous membranes have been the subject of intense research from the point of view of fundamental properties and applications. A particular difficulty involves the conventional synthesis methods. For example, for doping graphene, numerous post-treatment methods have been used, such as atomic diffusion, chemical functionalization, sputtering, among others. Many of these methods generate materials with limitations in the level and type of doping, in addition to introducing defects and stress, which compromise the mechanical and electronic properties of the material. Another possibility involves growing the material with the shape and type of doping predetermined by chemical synthesis. This growth approach based on the bottom-up concept is achieved by Surface-Mediated Chemical Synthesis (SQMS) where organic precursors act as fundamental building blocks. The chemical synthesis based on the Ullmann reaction of halogenated organic precursors has allowed obtaining in a very efficient way the most varied forms of graphene (nanofibers, nanoflakes, nanodots, chevrons, porous networks, etc.) with atomic control of doping by heteroatoms. In addition to the appropriate organic precursor, the ordering depends strongly on the substrate. In this doctoral project, we will use some molecules previously doped with nitrogen, amine, and hydroxyl, to generate nanoporous graphene functionalized in specific sites and investigate its electronic properties, in particular the band structure. We will use template substrates, such as vicinal surfaces, which will allow the alignment of graphene ribbons, enabling characterizations of the band structure by the Angle-Resolved Photoemission Spectroscopy (ARPES) technique to be performed in the synchrotron. The synthesis of the samples, as well as the atomic and chemical characterization by Scanning Tunneling Microscopy and Scanning Tunneling Spectroscopy (STM and STS), in addition to photoelectron spectroscopy (XPS), will be performed in the surface physics system present in our laboratory. (AU)