A Novel Anisotropic Percolative Conductivity Transition in Thin Film Oxide Heterostructures

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Technical: This project aims for greater understanding of fundamental materials science issues in epitaxial growth and conduction mechanisms of thin-film heterostructures of conducting and insulating perovskite oxides that exhibit an anisotropic percolative conductivity transition tunable by film thickness, voltage and composition. The transition is thought to be similar to a metal-insulator transition but is additionally length dependent, involving electron localization triggered by a voltage bias. The approach includes transport measurements as a function of temperature and field (electrical and magnetic) under various conditions (film thickness, cell size, composition, electrode types) and material science synthesis and processing issues in materials combinations (electrodes, matrix:conductor, substrate) and to compare behaviors of materials combinations. Also, quantum mechanical modeling of electron transport along discrete elements consisting of contacts and conducting islands will be performed taking into account self energy, state occupancy (Fermi-Dirac) statistics and electrostatics (solving equivalent circuits made of essentially capacitors), and effects of charge trapping. Non-technical: The project addresses basic research issues in a topical area of electronic/photonic materials science with high technological relevance. It is considered a high risk/high potential pay-off project. The interdisciplinary nature of the research and the combined experiment and modeling approach provide additional opportunities for students to broaden their educational experience.