Size Effects on Optical and Electrical Properties of Ferroelectric Thin Films and Nano-Crystalline Materials

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9801759 Katiyar This project addresses basic relationships between processing, structure, and properties of ferroelectric thin films and nanocrystalline materials. Greater understanding of how growth conditions affect film structure (phase, strain, grain size, and inhomogeneity) and dielectric and FE properties is sought. New information will be acquired on film thickness/FE behavior, interfacial bonding, film orientation, FE fluctuations and phase transitions, stability of the perovskite phase, and order- disorder behavior relationships to phase transition dynamics. Studies of size effects on optical and electrical properties of perovskite-type ferroelectric (FE) thin films and nano-crystalline materials, such as PbTiO3, BaTiO3, Pb(Zr,Ti)03, (Ba,Sr)TiO3, (Pb,Ba)TiO3, (Pb,La)TiO3 are planned. Properties of these materials are strongly dependent on microstructure and grain size; hence FE nano-crystalline materials with different grain sizes will be prepared using Sol-Gel and conventional ceramic processing techniques. Grain size variation will also be studied by annealing samples at different temperatures and time durations. Deposition/growth of FE thin films with different thicknesses and substrates will be carried out using sol-gel, RF Sputtering, and pulsed laser deposition (PLD) techniques. Characterization will include several microscopies--XRD, XPS, SEM/TEM, EDX, and AFM, along with laser Raman confocal microprobe and FTIR microspectroscopy. Dielectric, hysteresis, piezoelectric, pyroelectric, electro-optic, and differential thermal measurements on films will be carried out to quantitatively assess opto-electronic and related physical properties. %%% The project addresses basic research issues in a topical area of materials science having high potential technological relevance. The materials to be studied possess large dielectric, pyroelectric, piezoelectric, and nonlinear optical coefficients that can be usefully exploited in opto-electronic and microe lectronic technologies (e.g., memories, smart microsensors and actuators, multi-layer capacitors, and electro-optical modulators). The research will contribute basic materials science knowledge at a fundamental level; the new knowledge and understanding gained from the research is expected to contribute to improving the performance and stability of advanced devices and circuits by providing a firm basis for designing and producing improved materials, and materials combinations. An important feature of the program is the integration of research and education through the training of graduate and undergraduate students in a fundamentally and technologically significant area. ***