Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.

Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Self assembly and interface chemistry of non-metallated tetraphenyl porphyrin

Geoffrey A Rojas, University of Nebraska - Lincoln

Abstract

The study of the electronic properties and geometrical arrangement of 5, 10, 15, 20-tetraphenyl-21H, 23H-porphine on metal is presented. The systems were analyzed using both scanning tunneling microscopy and photoelectron spectroscopy and compared across surfaces to determine how the interface chemistry between the metal and molecule affect the self-assembly and band structure of the adsorbed species. Themolecules are found to self-assemble and grow on the Ag(111) surface in a manner described by similar models to weakly bound metal/metal surface systems. The CH-pi bonds between molecules are found to largely determine the relative inter-molecular arrangement, while the more isotropic van der Waals interactions drive the self-assembly. The 2H-TPP however remains isolated and equally dispersed despite any increases in coverage, observed motion, or annealing on the Cu(111) surface, indicating an electrostatic repulsion between adsorbates. Through calculation, spectroscopic observations of state shifts and mapping of the local work function, the limiting factor in the inter-molecular repulsion is found to be due to a combination of charge transfer between molecule and surface and perturbation of the surface electrons due to frontier orbital overlap. By comparing this molecule across surfaces and temperatures, the complex interplay between band structure matching, charge transfer, surface barriers, and self-assembly is described. Controlling the charge transferred to the adsorbed species by the underlying metal, these properties are tailored without changing the atomic constituents or general band structure of the adsorbed species.^

Subject Area

Physics, Low Temperature|Physics, Condensed Matter

Recommended Citation

Rojas, Geoffrey A, "Self assembly and interface chemistry of non-metallated tetraphenyl porphyrin" (2011). ETD collection for University of Nebraska - Lincoln. AAI3481627.
http://digitalcommons.unl.edu/dissertations/AAI3481627

Share

COinS