Self-Assembled Polydomain Ferroelectric and Ferromagnetic Heterostructures

该项目是对薄膜/衬底异质结构中自组装氧化物多畴结构的理论和实验研究。衬底上薄膜的多畴结构在很大程度上取决于它们的机械约束：薄膜与衬底之间的不匹配，薄膜/衬底界面的方向和局部结构，以及薄膜的几何构型。本研究的目标是通过约束工程设计可控多畴结构，以获得增强的铁电和铁磁薄膜材料的功能性能。约束工程的不同技术（修改薄膜/衬底不匹配，薄膜和薄膜/衬底界面的图案化）将被用来实现这一目标。这些技术将在PbTiO3-Pb(Zn,Ti)O3 （PZT）四方薄膜上进行开发和测试，该薄膜具有很强的压电效应。随后，该技术将被应用于PZT系统中具有高自适应铁电体的膜，其成分接近于相变相边界。多畴工程还将应用于La1-xSrxMnO3系统的铁磁氧化物，该系统具有巨大的磁阻和有前途的磁致伸缩性能。通过理论、建模和实验验证相结合的方法，对理论得到的领域设计原理进行研究。理论工作将包括多畴结构的内应力和能量分析，非图像化薄膜的相场建模，以及局部应力效应和图像化薄膜的有限元分析。实验工作将包括薄膜加工、图像化薄膜工程、多畴结构设计及其x射线衍射、电子显微镜、扫描力显微镜和磁光成像技术的表征。薄膜的电、磁和机械性能也将进行测量。该项目涉及具有技术相关性的电子材料科学领域的基础研究问题。该项目的一个重要特点是非常重视教育，并将研究与教育相结合。综合资源，包括实验和理论方法，为参与高度跨学科前沿研究的研究生的教育和培训提供了特殊的机会

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.***