This Research Opportunities for Women Research Initiation Award project is in the general area of Analytical and Surface Chemistry and in the subfields of thin film deposition and inelastic tunneling spectroscopy (IETS). The IETS technique has been limited by the reactivity of the substrate materials commonly used and their tendency to decompose or reduce the adsorbate species. The Principal Investigator will synthesize, by ion-beam deposition, a broad spectrum of new insulating thin-film substrates with varying reactivity and electron-transfer properties suitable for application with IETS. The film materials will include metal oxides, metal nitrides, mixed metal oxides, and diamond-like carbon. Structural characterization of the films will be performed by electron microprobe analysis, transmission electron microscopy, infrared spectroscopy and IETS. Tunneling spectra of a number of adsorbed probe molecules will be measured in order to classify the substrate materials with respect to their barrier quality and chemical inertness. Electronic and vibrational spectroscopies utilizing photons as probes have contributed greatly to our knowledge of the structure, bonding and reactivity of materials. They are limited, however, by the selection rules that govern photon emission, absorption and scattering. Inelastic electron tunneling is not limited by these optical selection rules and is thus a powerful tool for spectroscopic characterization of adsorbed molecular species. Low-lying electronic transitions and both allowed and forbidden vibrational modes can be detected. Development of a catalog of insulating materials with sufficient diversity that virtually any molecular species can be matched to a relatively inert substrate for spectroscopic investigation will greatly enhance the general utility of this technique. It will find increased application both in fundamental molecular spectroscopy and in technologically relevant fields such as corrosion, adhesion, catalysis and microelectronic device fabrication.
