- Monnell, Jason D.
- Graduate Program:
- Doctor of Philosophy
- Document Type:
- Date of Defense:
- February 17, 2005
- Committee Members:
- Paul S Weiss, Committee Chair/Co-Chair
James Hansell Adair, Committee Member
Karl Todd Mueller, Committee Member
Thomas E Mallouk, Committee Member
atomic force microscopy
scanning tunneling microscopy
- Advanced materials have led to new and improved technologies. This dissertation investigates some fundamental structural and electronic properties of molecular surface coatings. The structures formed by alkaneselenolate molecules were observed to pack in two distinctly different surface morphologies in comparision to structures commonly formed by alkanethiolate molecules. Structural and electronic differences between these molecules were determined to originate specifically from the headgroup linking the molecule to the surface. The electronic contact resistances of these linkers (-S-Au and Se-Au) that connect molecules to Au were measured using a combination of scanning tunneling microscopy and apparent tunneling barrier height microscopy. Using the same methods, the conductance of selected individual molecules was measured and contrasted. Advanced inorganic materials were also investigated. Hydrothermally-grown PbTiO3 crystals were probed using scanning surface potential and piezoresponse microscopy. The piezoelectric hysteresis characteristics observed for PbTiO3 crystals were observed to be dependent on the material thickness, as no piezoelectric properties were observed for platelets thinner than 12 nm. Using similar techniques, the ferromagnetic properties of 10 nm - Fe2O3 nanoparticles were ascertained. Magnetic force microscopy data revealed that defects (including domain boundaries and second layers) have larger effects on the magnetic force observed than individual nanoparticles. Further, the second layer was observed to have stronger magnetic properties than the initial layer. These results demonstrate that changes which are perceived to be minute are actually very important and cause significant differences at the molecular scale. For devices to be manufactured at the molecular scale, these changes are crucial to understand and exploit.