title: Stepwise formation and characterization of covalently linked multiporphyrin-imide architectures on Si(100).
abstract: A major challenge in molecular electronics and related fields entails the fabrication of elaborate molecular architectures on electroactive surfaces to yield hybrid molecular/semiconductor systems. A method has been developed for the stepwise synthesis of oligomers of porphyrins linked covalently via imide units. A triallyl-porphyrin bearing an amino group serves as the base unit on Si(100), and the alternating use of a dianhydride (3,3',4,4'-biphenyltetracarboxylic dianhydride) and a porphyrin-diamine for reaction enables the rapid and simple buildup of oligomers composed of 2-5 porphyrins. The properties of these porphyrin "multad" films on Si(100) were interrogated using a variety of techniques. The charge densities of the redox-active porphyrin oligomers were determined via electrochemical methods. The stepwise growth was evaluated in detail via Fourier transform infrared (FTIR) spectroscopy and by selected X-ray photoelectron spectroscopic (XPS) studies. The morphology was probed via AFM methods. Finally, the thickness was evaluated by using a combination of ellipsometry and AFM height profiling, accompanied by selected XPS studies. Collectively, these studies demonstrate that high charge density, ultrathin, multiporphyrin films of relatively well-controlled thickness can be grown in a stepwise fashion using the imide-forming reaction. The increased charge densities afforded by the porphyrin multads may prove important for the fabrication of molecular-based information-storage devices. This bottom-up process for construction of surface-tethered molecular architectures complements the top-down lithographic approach for construction of functional devices with nanoscale dimensions.
authors.affiliation: Department of Chemistry, University of California, Riverside, CA 92521-0403, USA.
authors.forename: Jieying
authors.initials: J
authors.lastname: Jiao
authors.forename: Franklin
authors.initials: F
authors.lastname: Anariba
authors.forename: Hugo
authors.initials: H
authors.lastname: Tiznado
authors.forename: Izabela
authors.initials: I
authors.lastname: Schmidt
authors.forename: Jonathan S
authors.initials: JS
authors.lastname: Lindsey
authors.forename: Francisco
authors.initials: F
authors.lastname: Zaera
authors.forename: David F
authors.initials: DF
authors.lastname: Bocian