UC Berkeley

This dissertation focuses on the manipulation of the lattice degree of freedom in perovskite oxide thin films, and explores the fundamental structure-property relationships. Epitaxial thin-film engineering and state-of-the-art thin-film characterization techniques are employed to achieve an effective and quantifiable control over a number of structural features including lattice expansion/compression, lattice tilting, octahedral rotations, and surface structures. Henceforth, the detailed correlation between structural features and

corresponding physical properties are established and exemplified in several model perovskite systems. The key findings in this work include that, first, the interfacial structural coupling effect is explored and demonstrated in SrRuO3 thin films where the lattice symmetry,

magnetic anisotropy, and electrical transport can be readily controlled. Moreover, growth-mediated antisite defects are found to be responsible in determining the energy competition between the low-symmetry antiferroelectric and the high-symmetry ferroelectric phases in PbZrO3 thin films, and the metastable ferroelectric phase can be stabilized. In addition, detailed relationships between ionic charge transport and lattice structure is explored in LSGM, and in turn, an optimal design of perovskite structure for high ionic conduction is successfully demonstrated through epitaxial strain and interfacial engineering. And lastly, surface engineering via growth-orientation control is explored in LSCF to establish the correlation between surface structure and electrochemical activities.