Dissertation
Tailoring electronic properties in semiconducting perovskite materials through octahedral control
Doctor of Philosophy (Ph.D.), Drexel University
May 2017
DOI:
https://doi.org/10.17918/etd-7425
Abstract
Perovskite oxides, which take the chemical formula ABO₃, are a very versatile and interesting materials family, exhibiting properties that include ferroelectricity, ferromagnetism, mixed ionic/electronic conductivity, metal-insulator behavior and multiferroicity. Key to these functionalities is the network of BO₆ corner-connected octahedra, which are known to distort and rotate, directly altering electronic and ferroic properties. By controlling the BO₆ octahedral distortions and rotations through cationic substitutions, the use of strain engineering, or through the formation of superlattice structures, the functional properties of perovskites can be tuned. Motivating the use of structure-driven design in oxide heterostructures is the prediction of hybrid improper ferroelectricity in A'BO₃/ABO₃ superlattices. Two key design rules to realizing hybrid improper ferroelectricity are the growth of high quality superlattice structures with odd periodicities of the A / A' layers, and the control of the octahedral rotation pattern. My work explores the rotational response in perovskite oxides to strain and interface effects in thin films of RFeO₃ (R = La, Eu). I demonstrate a synchrotron x-ray diffraction technique to identify the rotation pattern that is present in the films. I then establish substrate imprinting as a key tool for controlling the rotation patterns in heterostructures, providing a means to realize the necessary structural variants of the predicted hybrid improper ferroelectricity in superlattices. In addition, by pairing measured diffraction data with a structure factor calculation, I demonstrate how one can extract both A-site and oxygen atomic positions in single crystal perovskite oxide films. Finally, I show results from (LaFeO₃)_n/(EuFeO₃)n superlattices (n = 1-5), synthesized to test the motivating predictions of hybrid improper ferroelectricity in oxide superlattices.
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Details
- Title
- Tailoring electronic properties in semiconducting perovskite materials through octahedral control
- Creators
- Amber K. Choquette - DU
- Contributors
- Steven J. May (Advisor) - Drexel University (1970-)
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xviii, 188 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) (1970-2026); College of Engineering (1970-2026); Drexel University
- Other Identifier
- 7425; 991014632616904721