Scanning probe microscopies for the creation and characterization of interfacial architectures: studies of alkyl thiolate monolayers at gold

摘要

At this time, technology is approaching a point where molecular scale knowledge of interfacial architectures is required for further progress. The successful creation and characterization of functioning molecular scale architectures requires techniques which can probe the molecular structure and properties of these interfaces. Scanning probe microscopy (SPM) offers access to the structural and material properties of interfaces, and when combined with macroscopic characterization techniques results in a powerful interfacial development tool. However, the relative infancy of SPM techniques has dictated that initial investigations concentrate on model interfacial systems as benchmarks for testing the control and characterization capabilities of SPM. One such family of model interfacial systems results from the spontaneous adsorption of alkyl thiols to gold;This dissertation examines the application of SPM to the investigation of the interfacial properties of these alkyl thiolate monolayers. Structural investigations result in a proposed explanation for counterintuitive correlations between substrate roughness and heterogeneous electron transfer barrier properties. Frictional measurements are used for characterization of the surface free energy of a series of end-group functionalized monolayers, as well as for the material properties of monolayers composed of varying chain length alkyl thiols. Additional investigations used these characterization techniques to monitor the real-time evolution of chemical and electrochemical surface reactions;The results of these investigations demonstrates the value of SPM technology to the compositional mapping of surfaces, elucidation of interfacial defects, creation of molecularly sized chemically heterogeneous architectures, as well as to the monitoring of surface reactions. However, it is the future which will demonstrate the usefulness of SPM technology to the advancement of science and technology. These investigations are only a prelude to the more adventurous applications to molecular manufacturing, mechanically directed molecular synthesis, and other directions in the rapidly evolving fields of nanotechnology. While SPM will assist in controlling and understanding our current micro-technologies, it will be most crucial to the next wave of the technological development for emerging molecular scale technologies.