Characterization of the porphyrinic architectures for use in molecular information storage applications

The focus of this work is the design and characterization of a series of porphyrinic and related architectures to develop molecular memory devices. Such memory devices have several advantages such as high density, low power consumption, high level of stability, and ease in fabrication. The properties of the memory devices were optimized by tuning the molecular structures (i.e. redox-active center, linking group, and anchoring atoms) via chemical synthesis and modifying substrates. The electrical behavior and structural information of the molecules were characterized using a number of techniques including X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and various electrochemical methods.; The first work described in this thesis is the characterization of a series of molecules bearing a tripodal thiol-terminated tether. The electon-transfer kinetics and charge-retention properties of these molecules are generally similar as those of molecules with single thiol tether. Structural characterization reveals that not all of the three thiols bind to the surface. The second work described herein is the study of a number of carbon-tethered porphyrin monolayers on Si(100), the goal being the development of a hybrid semiconductor/molecular memory device. Electron-transfer rates, charge-retention times and structural information were compared between different linking groups. The electrolyte effects on the kinetic properties were also studied on selected molecules, charge storage device, a novel carbon tripodal allyl tether was designed based on the results of the studies on the tripodal thiolated tether. The surface coverage of porphyrin and triple-decker monolayers with this tether increases ∼3 fold versus that obtained using mono-carbon tethers. The properties of redox-active monolayers on different substrates have also been investigated in the course of these studies.; Collectively, the studies reported herein demonstrated that electron-transfer rates and charge-retention times can be tuned by changing the redox center, linking group, and/or substrates, but not the anchoring atoms. The structures of the linking group have a large effect on the charge-density and adsorption geometry. These findings will provide fundamental parameters in the molecular design and surface modification for molecular memory applications.