Biography
Biography: Axel Enders
Abstract
Low-dimensional functional organic materials are currently the subject of intensive research, due to their unusual, unique or superior electronic properties, and due to their potential applicability in all-organic electronics. Graphene, hexagonal boron nitride, molybdenum sulphide and other transition metal dichalcogenides are popular examples of atomically thin materials that show great promise for various applications. Interestingly, another class of materials, organic ferroelectrics, can also be synthesized as two-dimensional layers and even as one-dimensional chains, retaining their ferroelectric properties while being amenable to great level of structural and properties design, as will be shown in this talk. It is discussed how atomically thin structures of molecules from known hydrogen-bonded room-temperature ferroelectrics can be synthesized on crystalline surfaces through selfassembly. Those structures include 1D molecular chains, 2D homogeneous networks, and 2D cocrystals. Properly designed, cocrystals allow for asymmetric hydrogen bonds, to build materials with a hierarchy of barriers to proton transfer that could in principle exhibit multiple and complex polarization states. First principlses calculations were employed to study polarization behavior at the molecular level. Calculations based on density functional theory predict that polarization reversal in such chains can occur through proton tautomerization, where the substrate appears to determine the height of the barrier to intermolecular transfer of hydrogens along the hydrogen bonds. It is predicted that hydrogen-bonded organic ferroelectrics can be engineered into 2D and 1D structures while not only retaining their ferroelectric functionality, moreover, the substrate can act as an additional control parameter to control the ferroelectric properties.