Self-Assembled Polydomain Ferroelectric and Ferromagnetic Heterostructures

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The project is a collaborative theoretical and experimental study of self-assembled oxide poly-domain architectures in film/substrate heterostructures. The polydomain structures of thin films on substrates are strongly determined by their mechanical constraints: the misfit between the film and substrate, the orientation and local structure of the film/substrate interface, and the geometri-cal configuration of the film. The goal of this research is to design controlled polydomain struc-tures through constraint engineering to obtain enhanced functional properties of ferroelectric and ferromagnetic film materials. Different techniques of constraint engineering (modification of film/substrate misfit, patterning of films and film/substrate interfaces) will be employed to achieve this goal. These techniques will be developed and tested on PbTiO3-Pb(Zn,Ti)O3 (PZT) tetragonal films, which demonstrate strong piezoeffects. Subsequently, the techniques will be ap-plied to films of highly adaptive ferroelectrics with compositions near the morphotropic phase boundary in the PZT system. Polydomain engineering will also be applied to ferromagnetic oxides of the La1-xSrxMnO3 system, which exhibit colossal magneto-resistance and promising mag-netostrictive properties. The research objectives are sought through a combination of theory, modeling and experimental verification of theoretically obtained domain design principles. Theo-retical work will include analysis of internal stresses and energetics of polydomain structures, phase field modeling for non-patterned films, and finite element analysis (FEM) for local stress effects and patterned films. The experimental work will consist of thin-film processing, engi-neering of patterned films, design of polydomain structures and their characterization by X-ray diffraction, electron microscopy, scanning force microscopy and magneto-optical imaging tech-nique. Measurement of electric, magnetic and mechanical properties of films will also be per-formed. %%% The project addresses fundamental research issues in areas of electronic materials science having technological relevance. An important feature of the project is the strong emphasis on education, and the integration of research and education. The combined resources, including experimental and theoretical methods, provide special opportunities for education and training of graduate stu-dents involved in highly interdisciplinary forefront research.***