Scanning tunneling spectroscopy of fullerene nanostructures

This dissertation presents a scanning tunneling microscopy and spectroscopy study of fullerene molecules on metal surfaces. The basic driving questions behind this work are (1) how does local molecular electronic structure respond to a condensed matter environment (i.e. a surface interface), (2) can molecular electronic structure be tuned at the single molecule level through local perturbations, and (3) how do electron-electron and electron-phonon interactions affect transport through molecules? These questions are important not only for developing a basic understanding of molecular electronic behavior, but also for exploring fundamental issues in future molecular device construction. A main result in this dissertation is that molecular electronic and vibrational structure is intrinsically inhomogeneous at the angstrom (10 -10 m) level. As a consequence, future molecular-based devices must take into account this molecular inhomogeneity, rather than simply spatially averaged quantities like molecular orbital energy level alignment.; Two general molecular configurations were experimentally investigated: single molecule systems and molecular layer systems. The single molecule section examines the local electronic structure of single fullerenes on a Ag(001) substrate and their response to perturbations, such as electron doping and electron-phonon coupling. The molecular layer section examines the local morphology and electronic structure of monolayers and bilyers of C60 molecules on Ag(001).