Observation of Domain Switching in Fatigued Epitaxial Pb(Zr,Ti)O 3 Thin Films
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Observation of Domain Switching in Fatigued Epitaxial Pb(Zr,Ti)O3 Thin Films Yong Kwan Kim, Shintaro Yokoyama, Risako Ueno, Hitoshi Morioka, Osami Sakata1, Shigeru Kimura1, Keisuke Saito2, and Hiroshi Funakubo Department of Innovative and Engineered Materials, Tokyo Institute of Technology, Japan. 1 Research & Utilization Division, Japan Synchrotron Radiation Research Institute/ SPring-8, Japan. 2 Application Laboratory, Bruker AXS, Japan. ABSTRACT We performed x-ray diffraction measurements by using highly brilliant synchrotron radiation on epitaxial Pb(Zr0.35Ti0.65)O3 film capacitor structures. Small regions of 300-nm-thick epitaxial Pb(Zr,Ti)O3 thin films with Pt and SrRuO3 top electrodes were measured after applying various numbers of switching cycles of the electric field. Epitaxial Pb(Zr,Ti)O3 thin films were prepared on epitaxial (100)cSrRuO3/(100)SrTiO3 substrates by pulsed-metalorganic chemical vapor deposition. The volume faction of c-domain and remanent polarization was plotted against the number of switching cycles. In the both capacitors, the Vc increased as the switching cycle increased independent of fatigue behavior. INTRODUCTION Ferroelectric thin films of lead based perovskite materials such as PbTiO3, (Pb,La)TiO3 (PLT), Pb(Zr,Ti)O3 (PZT), etc. have received considerable attention for their attractive physical properties including high dielectric, pyroelectric, piezoelectric, and electro-optic properties[1,2]. The domain structure and their switching dynamics are coupled together and their interplay is of great importance in various practical applications such as nano-storage devices, microelectromechanical systems (MEMS) and actuators.[3] In order to take full advantage of anisotropic properties through alignment of the polar axis, epitaxial film growth of the ferroelectric materials is essential to optimize the device performance through the polar axis and elimination of the detrimental structural defects, which prevents the residual-domain generation and reduces an optical scattering due to the absence of domain wall. In a heteroepitaxial tetragonal ferroelectric thin film on a cubic oxide single-crystal substrate, a/c/a/c-polydomain structure forms during cooling prior to the cubic-to-tetragonal transformation near the Curie temperature to relieve the misfit strain energy between the cubic and the tetragonal phase.[4–7] In this case, the a domains form through four coherent {101} twinning, and twin planes become the c/a-domain boundary. 90o-domain switching gives rise to field-induced change in birefringence and strains required for electro-optic and piezoelectric devices, respectively, However, 90°-domain switching under electrical potential field remains quite controversial where is the origin of degradation such as fatigue in ferroelectric random
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access memory (FRAM) application. As such, it is very important to evaluate the domain switching behavior in the epitaxial thin films under mechanical or electrical potential field. X-ray diffraction (XRD) is advantag
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