****NON-TECHNICAL ABSTRACT**** Modern science and technology of electronic materials increasingly focuses on the development of novel, artificially engineered structures on the nanometer (one billionth of a meter) scale. The physical behavior of materials at the nanoscale is principally different from that of macroscopic materials in many aspects, opening new opportunities for the design of materials with superior properties for device applications. This project will experimentally investigate the fundamental physical properties of nanoscale ferroelectrics and multiferroics, an interesting and practically important class of electronic materials with high potential for applications in various devices, such as computer memories or microwave electronic devices. The project will utilize optical spectroscopic techniques to probe fundamental properties related to the atomic vibrations and structural transformations under a variety of conditions. The experimental results of the project will test the validity of current theories of ferroelectrics and multiferroics, thereby contributing to a comprehensive understanding of their properties. The proposed research will be closely integrated into the educational program at Boise State University, involving undergraduate and graduate students in research and training, promoting an active use of the state-of-the-art optical instrumentation for educational purposes, and supporting the development of new graduate programs.
Ferroelectrics are materials possessing a spontaneous electric polarization, which can be switched by the application of an electric field. Ferroelectrics and multiferroics, materials that exhibit both magnetic and ferroelectric ordering, are the focus of much active research with an abundance of basic science to be studied and novel applications to be explored. In recent years, science and technology of ferroelectrics and multiferroics have moved towards artificially engineered thin films and multilayer structures at nanometer scales. The dynamics of lattice vibrations is a fundamental property of ferroelectrics, related to many of their important physical properties, and Raman spectroscopy is one of the most powerful analytical techniques for studying the lattice vibrations. This project will utilize ultraviolet Raman spectroscopy to address several issues of major importance for understanding the behavior of nanoscale ferroelectrics and multiferroics, such as temperature-strain phase diagrams of thin films and heterostructures, the effect of an electric field on lattice dynamics and phase transitions, effects of off-stoichiometry on the properties of homo- and heteroepitaxial ferroelectric films, and ferroelectric and structural transformations in strained films of novel materials. The proposed research will be closely integrated into the educational program at Boise State University, actively involving undergraduate and graduate students in research and training and promoting the continued effective use of the state-of-the-art optical instrumentation for educational purposes.
The project outcomes in Intellectual merit consist of several important results concerning the fundamental physics of nanoscale ferroelectrics and multiferroics, an interesting and practically important class of electronic materials with high potential for applications in various devices, such as non-volatile computer memories or microwave devices. Understanding physical behavior of materials at nanoscale is essential for modern science and technology of electronic materials, which focuses increasingly on the development of novel artificially engineered structures at nanometer scale. Physical properties at nanoscale are principally different from those of macroscopic materials in many aspects, which opens new opportunities for design of materials with superior properties for device applications. Our project utilized optical spectroscopic techniques using ultraviolet laser light to probe some fundamental properties of nanoscale ferroelectrics and multiferroics, related to the atomic vibrations and structural transformations under different conditions. These results, combined with theoretical predictions, advancements in synthesis and other characterization techniques made by our collaborators, contributed to a more comprehensive understanding of practically important properties of ferroelectric and multiferroic materials, sich as barium titanate, strontium titanate, and bismuth ferrite.Our research makes significant scientific impact in other disciplines, from optical spectroscopy and microscopy of wide-bandgap semiconductor materials and nanostructures to the synthesis of multifunctional oxide materials; from first principles and thermodynamic theories receiving much needed experimental feedback to device applications of ferroelectric and multiferroic materials with artificially engineered properties. The project has numerous broader outcomes beyond its specific scientific field. Our research activities have been closely integrated into the educational program at Boise State University involving 5 undergraduate and one graduate students in research and training. BSU students involved in the project participated in cutting-edge research using state-of-the-art instrumentation, developd their technical communication skills by writing research papers and presenting their results at major international conferences, such as American Physical Society and Material Research Society meetings. As a result, the students became well prepared for their future careers in science and engineering. In addition to direct student training, the project promotied an active use of the state-of-the-art optical instrumentation for educational purposes, in physics and materials science courses taught at BSU. The research program enhanced graduate research opportunities for a new interdisciplinary PhD program in Materials Science and Engineering recently opened at BSU. Optical spectroscopy instrumentation operated and maintained with the support from this grant, constitutes a valuable research resource utilized by other BSU scientists in their research projects. We use the facilities of our optical spectroscopy laboratory in a variety of outreach activities for high school students and science teachers, aimed at attracting more talented students from Boise metropolitan area to STEM (science, technology, engineering and math) disciplines.
