Center for Functional Nanomaterials Seminar

As the demand for smaller and faster electronics increases, organic molecules that can function as electronic devices have become a hot topic in the experimental research arena. Scanning tunneling microscopy (STM) is capable of probing the structural and electronic properties of nanoscale materials on surfaces at an atomic scale by combining a variety of STM manipulation schemes with tunneling spectroscopy techniques. This talk will focus on the recent results of single molecules using ultra-high vacuum low-temperature STM (UHV LT-STM) and will cover a broad area including molecular spintronics, molecular charge transfer systems, and molecular machines that have the potential use in molecular electronics. In the first part of my talk, LT-STM and spectroscopy study of single molecular level charge transfer complexes (CTCs) will be presented. The complexes are formed by self assembly of the electron donor α-sexithiophene (6T) and the electron acceptor tetrafluro-tetracyano-quinodimethane F4TCNQ on a Au (111) surface. The formation of new hybrid molecular orbitals in CTCs is evident by STM imaging at different bias voltages as well as by differential conductance spectra. In the spintronic area, I will present an extensive and unusual redistribution of spin density of cobalt porphyrin (TBrPP-Co) molecules adsorbed on a Cu(111) surface. Here, charge injection from the surface to the molecule can result in redistribution of molecular spin to the organic ligands, hence the entire molecule becomes magnetic. This effect was confirmed by monitoring the Kondo temperature with differential conductance (dI/dV) tunneling spectroscopy and spectroscopic mapping. Finally, in the molecular nanomachines area, complex rotation mechanisms of Ru based double-decker molecular rotor induced by inelastic tunneling electrons will be presented. Understanding the basic science behind these new systems will allow a determination of their viability for future applications.