Processing and characterization of ferroelectric nanostructures

Department of Materials Science and Engineering, Pohang University of Science and Technology, KOREA* Pohang Accelerator Laboratory, Pohang University of Science and Technology, Korea** Max Planck Institute of Microstructure Physics, Germany***
â—‹Songhak Yoon* Hee Han* Yongjun Park** Min Gyu Kim** Namsoo Shin** Ran Ji*** Dietrich Hesse*** Marin Alexe*** Kornelius Nielsch*** Ulrich Goessele*** Sunggi Baik*

This presentation will focus on recent findings related to the process and analysis of ferroelectric nano-materials. In the first example, the influence of lattice expansion on the crystal structural changes of the BaTiO3 nanoparticles have been studied by X-ray diffraction and X-ray absorption near edge structure via synchrotron radiation. BaTiO3 nanoparticles are synthesized by hydrolysis and condensation of mixed isopropanol solution of barium hydroxide octahydrate and titanium (IV) isopropoxide. The BaTiO3 nanoparticles synthesized without additional water showed anomalous lattice expansion and high tetragonality. As extra water is introduced and its amount is increased, Rietveld analysis confirms that the crystal structures of BaTiO3 nanoparticles change gradually from tetragonal to cubic structure. Change in peak intensities at the titanium pre-edge region in XANES also indicates that highly distorted TiO6 octahedra are gradually relaxed with water addition.
In the second example, well-ordered Pb(Zr0.2Ti0.8)O3 nanostructures with the lateral size ranging from 400 nm to 100 nm were fabricated on SrRuO3 bottom electrode on SrTiO3 single crystal substrate using laser interference lithography (LIL) process combined with pulsed laser deposition. Transmission electron microscopy confirmed that (001)-oriented PZT nanostructures were grown epitaxially on (001)-oriented single crystal substrate covered with epitaxial SrRuO3 (001) bottom electrode layer. Anisotropic ferroelectric properties of each PZT nanostructure were characterized by scanning force microscopy and the evolution of domain structures as a function of thickness and width of PZT nano-islands was characterized by reciprocal space mapping using synchrotron X-ray diffraction.