Manipulative Scanning Tunneling Microscopy and Molecular Spintronics
Nanoscale systems, at the intersection of bottom-up and top-down approaches to technological development, have demonstrated unique properties and applications in recent scientific studies. Scanning probe microscopy has emerged as a versatile tool for studying nanoscale interactions due to its capabilities of local measurement of spectroscopic, magneto-electric, and topographic properties in real-space with sub-nanometer resolution. Still, many physical and chemical effects have yet to be completely characterized and understood. This dissertation demonstrates the novel application of scanning tunneling microscopy to the study of local work functions through field emission resonances, surface catalyzed covalently bound chain formation, and spintronic interactions of organically coupled magnetic ions. Local work functions are found, by analyses of field emission resonances, for probe induced surface vacancies and atomic step edges on an atomically clean Ag(111) crystal. The extracted local work functions for defect locations vary significantly from the known and measured clean surface values. The local work function plays a large part in surface binding and electronic interaction of surface adsorbates. This technique for local work function measurement can be extended to more unique surface and molecular systems. A process for the formation, and topographic measurement, of covalently bound chains by surface catalysis is demonstrated with homogeneous magnetic and heterogeneous networks of molecules. The chain coupling occurs through an Ullmann-like halogen substitution and subsequent ring coupling reaction mediated by surface atoms, with application of adequate thermal energy. Individual molecules with central magnetic ions are shown to exhibit a Kondo resonance in spectroscopic measurements. Covalently bound chains of these molecules maintain the Kondo interaction while developing an antiferromagnetic coupling between the central magnetic ions as demonstrated through theoretical and spectroscopic techniques. The measurements of magnetic interaction and spin-communication along a covalently bound chain of molecules can be extended with transport and spin-polarized measurements. Together the techniques and results presented here demonstrate novel physical phenomena at atomic and molecular scales, by utilizing the versatility of scanning tunneling microscopic techniques, with implications for both fundamental scientific principles and applications.
Physics, Condensed Matter Physics, scanning tunneling microscopy, STM, Kondo effect, molecular spintronics, work function, surface science, molecular chains
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