Interface induced electric phenomena at the nanoscale

Maxim Pavlovich Nikiforov, University of Pennsylvania

Abstract

The goal of this research is to determine the influence of interfaces on local electrical properties in porphyrin monolayers on highly oriented pyrolytic graphite (HOPG) and lipid–peptide porphyrin layers on HOPG. Here, the effects of molecular orientation on work-function and the effect of light polarization on scattering cross-section of the porphyrin/HOPG system were determined. It was found that the dipole moment forming at the interface between a porphyrin ring oriented parallel to the HOPG surface decreases the work function by 50 mV; when the porphyrin ring oriented perpendicular to the surface such an effect was not observed. A method for the determination of the dielectric constants of organic monolayers was developed. It was shown that high-harmonic s-NSOM measurements using polarized light together with mathematical modeling of s-NSOM contrast using Maxwell equations provides enough information for the determination of real part of monolayer dielectric constant, when the s-NSOM is properly calibrated. Finally a technique to measure the electrical properties of compliant samples was developed. In this technique an AFM tip was used as one of the electrodes for electrical measurements. Electrical impedance between biased samples and grounded tips were measured. The technique was proven to work on lipid–peptide–heme films with high spatial resolution (better than 200 nm).

Subject Area

Materials science

Recommended Citation

Nikiforov, Maxim Pavlovich, "Interface induced electric phenomena at the nanoscale" (2008). Dissertations available from ProQuest. AAI3309486.
https://repository.upenn.edu/dissertations/AAI3309486

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