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Date of Award

Fall 2012

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Materials Science and Engineering

Supervisor

Gianluigi A. Botton

Language

English

Abstract

Strontium titanate (SrTiO3) has a wide range of applications in the electronic industry and attracts growing world-widely interest recently because of novel discoveries at its surfaces, interfaces and with selected dopants. The understanding of some of the structural properties of SrTiO3 and its optical properties have been lagging due to limited characterization techniques available to study single monolayers and dopants in this material.

In the present thesis, pure SrTiO3 single crystals with (2x1) and c(4x2) surface patterns were synthesized and samples (Pr, Al) doped SrTiO3 were prepared through ion implantation. The atomic and electronic structures of these samples were investigated by various high-resolution imaging and spectroscopic techniques available in an aberration-corrected transmission electron microscope. Particularly, the direct imaging of individual light atoms and vacancies within a bulk material containing heavier elements was demonstrated for the first time via the STEM-annular dark-field (ADF)/annular bright-field (ABF) images. In addition, the first electron energy-loss spectroscopy (EELS) 2-dimensional maps of dopants located in a lattice were obtained. These results provided a solid foundation regarding the mechanism of red light emission in doped SrTiO3. More importantly, a new experimental approach allowing the effective extraction of weak EELS signals from low-dimensional defects was developed and successfully applied to understand the chemical state and coordination of Ti cations within a single monolayer on a reconstructured SrTiO3 surface and the local defect configurations of injected Pr+ and Al+ ions within SrTiO3 single crystals.

Comments

I want delay publication of my dissertation until April 30 2013. Thanks.

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