Graphene SUPERlattice induced by ZwitterionIC supramolecular network – SUPERZIC

Engineering the band structure of a 2D material by imposing a superlattice moiré pattern has recently emerged as an effective approach to control quantum phenomena in condensed matter systems. Today these experiments are carried out only on inorganic van der Waals heterostructures wherein both the spatial modulation and the magnitude of its electrostatic potential of the resulting superlattice are definitively determined by those of the 2D inorganic layers. The concept of these heterostructures is versatile enough to envision the replacement of one inroganic layer by a 2D self-assembly of organic molecules. The resulting hybrid organic/inorganic heterostructure (h-vdW-H), will also form a superlattice with modulated spatial and potential properties. Our objective is to use the versatility of the chemical synthesis to control the formation of the superlattice and its related properties. This project aims at the development of hybrid organic/inorganic heterostructures based on self-assemblies of zwitterionic molecule deposited on graphene that allow an efficient patterning of the potential landscape of the 2D materials. Our methodology consists in exploiting the high degree of chemical engineering of the zwitterion that will allow a fine control of the superlattice thus created. This project is structured into 3 work package(WP). WP1 provide a reliable protocol for the synthesis of the h-vdW-H in Ultra-High-Vacuum. WP2 will be devoted to the characterization of these h-vdW-H and specially of the superlattice induced. The local effects of the molecular dipoles on the electronic structure of graphene such as modification of the electrostatic potential, electronic density, charge transfer, or eventually signature of a flat electronic band structure will be characterize at molecular scale with Scanning Probe Microscopy at Low-Temperature. At mesoscopic scale, doping and carrier mobility will be determined quantitatively by combining Hall and 4-probe measurements in clean room environment and vacuum and low and ambient temperature. These mesoscopic measurement will be completed by Micro-Raman mapping which will allow to access to the vibrational responses of graphene and adsorbed molecules even when integrated in electronic devices. Information such as the graphene average doping and strain induced by the presence of the molecular network will be extracted from the analysis and comparison of the graphene’s Raman responses before and after molecules’ deposition. All these studies will be supported by simulation during WP3. We will investigate the electronic structure of the supramolecular pattern formed by the zwitterionic molecules on graphene by ab initio calculations to assess the influence of the physisorbed zwitterionic molecules on the band structure of graphene. The final step of WP3 will be devoted to the simulation of quantum transport properties based on non-equilibrium Green’s function in the Landauer-Büttiker scheme implemented on a real-space tight-binding Hamiltonian. Throughout our investigations, we will look for the conditions of emergence of flat bands and investigate the possible signature of electronic correlated behavior in our h-vdW-H.