Date of Award

January 2014

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics & Astrophysics

First Advisor

Nuri Oncel

Abstract

Studies were performed on two seemingly different topics, molecular thin films on graphite/graphene and metal induced changes in various cuts of silicon (Si) surfaces. However, both projects share the underlying theme of self-assembly. Since nature can rely upon self-assembly at the nano-scale, all that is needed is to discover functional means to create components for integrated circuits as well as electronic and photonic devices.

Scanning Tunneling Microscopy and Spectroscopy (STM/STS) studies were carried out to characterize the morphology of thin porphyrin films on graphite and the effects of Zn-Phthalocyanine (Zn-Pc) adsorption on the electronic properties of graphene. It was found that the metal atom complex of porphyrin molecules can determine the morphology, intermolecular forces and ability to create thin films on a graphite surface. Zn-Pc adsorption onto graphene shifts the position of the Dirac point with respect to Fermi level which leads to localized p- and n-type doping effects in the graphene substrate.

STM, STS and Low-Energy Electron Diffraction (LEED) measurements were carried out on iridium (Ir) modified Si(111) and Si(100) surfaces. The Ir-modified Si(111) surface exhibited a √7×√7 R19.1° domain formation that was composed of Ir-ring clusters. LEED measurements showed that on Ir-modified Si(100), a p(2×2) structure arose after annealing at ~700℃. The proposed model for the Ir-silicide nanowires shows that an Ir atom replaces every other Si dimer along the Si dimer rows of Si(100)-2×1.

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