From Atomic Scale Strain Probing to Smart 3D Interface Design

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NON-TECHNICAL DESCRIPTION: The project explores the fundamental understanding of atomic-scale strain at heterogeneous interfaces which allows the design of nanostructures with new or significantly improved materials properties. This study is having direct impact on advanced materials (in thin film form) for memories, data storage devices, superconductors, and solid oxide fuel cells. The fundamental knowledge gained is also shedding light on the interfacial phenomena observed in many other ceramic nanocomposite systems with heterogeneous interfaces such as microelectronic and optoelectronic devices, thin film solar cells, etc. The education and outreach activities are integrated with the research (in particular, with the strain mapping results) and include: (1) further development of a teaching model "The Art of Laying Apples", (2) multidisciplinary training of undergraduate and graduate students at Purdue University and national laboratories, and (3) dissemination of research results to a much broader audience through a high school teacher's research program, on-campus outreach activities and a research website for all self-learners and materials scientists. TECHNICAL DETAILS: The project focuses on the design, synthesis, and characterization of heterogeneous interfaces in epitaxial ceramic nanocomposites, in particular on the atomic structure and strain distribution at the lateral and vertical interfaces. The goal of the project is to achieve oxide-based 3-dimensional (3D) strained hetero-structures by exploring the nature of lateral and vertical strained interfaces. These new materials are expected to have enhanced physical and chemical properties as ferroelectrics, multiferroics, superconductors, and ionic conductors. The specific tasks are: (1) conducting an atomic scale quantitative strain mapping/analysis on new layered oxide systems (e.g., Bi3Fe2Mn2Ox (BFMO)-based systems), (2) exploring the strain evolution in vertically aligned nanocomposites (VAN) (e.g., BiFeO3 (BFO) and La0.7Sr0.3MnO3 (LSMO)-based VAN systems), and (3) achieving 3D interface designs by combining the aforementioned lateral and vertical nanostructures. All the oxide thin films are being prepared by pulsed laser deposition (PLD). Various characterization techniques such as high resolution X-ray diffraction (XRD), combined geometric phase analysis-scanning transmission electron microscopy (GPA-STEM) for strain mapping and electrical and ionic transport property measurements are being used. It is anticipated that the fundamental strain study could reveal the growth mechanisms of these complex systems. Moreover, development of new 3D heterogeneous oxide thin films could lead to novel functionalities with 3D interface designs including enhanced ferroelectric and multiferroic properties, electron transport path for enhanced magnetoresistance properties, and ionic conductors for electrochemical cells.