Control and Manipulation of Polarization and Electric Fields at Complex Oxide-Semiconductor Interfaces

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Technical: The goal of the project is to control and manipulate polarization and electric fields at interfaces of crystalline oxides and semiconductor material. Key to achieving this goal is atomic level control of the microscopic form and structure of the interface, which requires advanced oxide molecular beam epitaxy (MBE) growth techniques. The research requires specialized characterization tools to probe buried epitaxial interfaces with the highest reciprocal space resolution, including high speed methods of measuring the crystal truncation rods of interface structures using synchrotron x-ray diffraction. Other physical and electrical structure characterization techniques include in-situ electrical transport measurements, in-situ surface diffraction and photoelectron spectroscopy, x-ray absorption spectroscopy, and transmission electron microscopy. The PIs combine these synthesis and characterization tools to develop new functional behavior in three specific areas: band offsets (interface dipoles), interface polarization, and single layer interface ferroelectrics. Each research direction is focused on a materials system suited to the relevant property under investigation: BaO for band offsets, SrTiO3 for interface polarization, and MX2-type layered films for ferroelectricity. The research addresses the fundamentals of how form (structure) affects function (electrical properties) at crystalline oxide-semiconductor interfaces. By considering crystalline oxides, one can apply a battery of atomic level control and structural characterization techniques to achieve a level of understanding of the microscopic structure that is not possible with amorphous oxides. Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance. The research has the potential to transform the utility of semiconductor structures by engineering and tailoring the properties of crystalline oxide-semiconductor interfaces at the atomic layer level. A key component of the project involves undergraduate and post-baccalaureate STEM (science, technology, engineering, and mathematics) participation in the implementation and practice of these techniques. Undergraduates grow materials using oxide MBE in both classroom and research environments and characterize these materials using synchrotron scattering techniques. The STEM graduates are involved in the engineering development and improvement of the synthesis and characterization techniques. This project is aimed at enhancing the technical skills of STEM graduates whose career goals are to transition to permanent technical positions in industry.