Characterization of Molecular and Atomic Species Adsorbed on Ferroelectric and Semiconductor Surfaces

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Title: Characterization of Molecular and Atomic Species Adsorbed on Ferroelectric and Semiconductor Surfaces
Author: Bharath, Satyaveda Chavi
Advisors: Mark Luo, Committee Member
Thomas Pearl , Committee Chair
Gerd Duscher, Committee Co-Chair
Nadia El-Masry, Committee Member
C. Lewis Reynolds, Committee Member
Abstract: BHARATH, SATYAVEDA CHAVI. Characterization of molecular and atomic species adsorbed on ferroelectric and semiconductor surfaces. (Under the direction of Thomas P. Pearl and Gerd Duscher). In order to clarify the mechanisms behind the adsorption of atomic and molecular species adsorbed on ferroelectric surfaces, single crystalline lithium niobate (LiNbO3, LN), ‘Z-cut’ along the (0001) plane, has been prepared, characterized and subsequently exposed to molecular and atomic species. 4-n-octyl-4′-cyanobiphenyl (8CB) liquid crystal was chosen as a polar molecule for our model system for this study. Low-energy electron diffraction (LEED), atomic force microscopy (AFM), surface contact angles (CA), and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface of LN as well as the nature of the liquid crystal films grown on the surface. Atomically flat LN surfaces were prepared as a support for monolayer thick, 8CB molecular domains. Also, for the purpose of gaining a fundamental understanding of low coverage interactions of metal atoms on ferroelectric surfaces, we choose to deposit gold onto the LN surface. These gold atomic layers were grown under UHV conditions and characterized. Understanding anchoring mechanisms and thin film organization for LC molecules and metal atoms on uniformly poled surfaces allows for a fuller appreciation of how molecular deposition of other polarizable molecules on patterned poled LN surfaces would occur as well as yielding greater insight on the atomic characteristics of metal on ferroelectric interfaces. Also, to reveal the mechanisms involved in the adsorption of organic aromatic molecules on high-index Si surfaces, thiophene (C4H4S) and pyrrole (C4H5N) molecules were dosed on prepared Si(5 5 12)-2x1 surfaces as our experimental system. The Si(5 5 12) surface was prepared to produce a 2x1 reconstruction after which molecules were dosed at low exposure to observe the preferred adsorption sites on the surface. All surface preparation and experiments were performed in UHV and measurements of the surface before and after deposition were performed using scanning tunneling microscopy (STM). Fundamental understanding of organic nanostructures on Si(5 5 12) surfaces will yield a broader appreciation of the mechanisms that drive the creation of these nanostructures for specific potential applications.
Date: 2009-07-27
Degree: PhD
Discipline: Materials Science and Engineering

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