Doctor of Philosophy (PhD)



Document Type



Naturally self-assembled mesospheres provide a practical route for controlling the arrangement of materials on surfaces at the nanoscale. Periodic arrays of well-defined nanostructures can be produced with different nanomaterials and interpattern spacings. Results presented in this dissertation demonstrate particle lithography methods developed for fabricating arrays of organosilane nanostructures. Surfaces were designed for the selective deposition of polymers and nanoparticles to produce multicomponent nanopatterns. The approaches for surface patterning provide new directions for studying surface chemistry at the molecular-level, and have practical application for emerging photovoltaic thin film technologies. Atomic force microscopy (AFM) provides unique capabilities for molecular visualization and ultrasensitive measurements of surface properties with nanoscale resolution. Organosilane nanopatterns bearing different functionalities and chain lengths were characterized using AFM to gain insight on molecular organization and surface-assembly processes. Indirect magnetic modulation (IMM) is a new instrument configuration for force modulation AFM that was developed for investigating mechanical properties of materials. The principle of IMM is based on indirect oscillation of soft nonmagnetic cantilevers through the tip holder assembly, which contains magnetic materials. Imaging can be performed in either ambient or liquid environments. The driving frequency for tip vibration can be selected to enhance contrast in amplitude and phase images, which provides information on the elastic response of thin-film materials. Images acquired with IMM furnish nanoscale resolution views of the morphology and elastic response of organosilane nanostructures. The dampening effect of liquid imaging media on cantilever oscillation during IMM was investigated using a liquid sample cell. Organic photovoltaic (OPV) devices are promising alternatives to traditional silicon based solar cells. A major challenge for OPVs is the requirement for higher efficiencies, or better device performance. The nanoscale morphology and molecular organization of the donor/acceptor materials in the organic layer affects the conductivity of OPV devices. To improve efficiency, new fabrication methods must be developed that are capable of controlling the molecular structure of the donor/acceptor materials. Using particle lithography combined with contact printing, billions of periodic and uniform pillar nanostructures of polythiophene can be fabricated on the surface. The dimensions and spacing can be selectively tuned by using different size latex masks.



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Committee Chair

Garno, Jayne

Included in

Chemistry Commons