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22 Jun 1998

Volume 72, Issue 25, pp. 3243-3383

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Electromechanical properties of sol-gel derived Ca-modified PbTiO3 films

A. Kholkin, A. Seifert, and N. Setter

Appl. Phys. Lett. 72, 3374 (1998); http://dx.doi.org/10.1063/1.121608 (3 pages) | Cited 27 times

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Piezoelectric coefficients and electric field-induced strains are investigated in Ca-modified PbTiO3 (PCT) films deposited by sol-gel technique. The microstructural evolution and related electromechanical properties are studied as a function of Ca content and porosity of the films. The porosity is tailored by changing the heating rate during the final crystallization anneal. It is found that piezoelectric properties of porous films heated at slow rates are superior to those of dense films crystallized using higher heating rates. This is explained as a result of the constraining effect of the substrate, which apparently reduces the piezoelectric and strain responses in dense films. Electromechanical properties are also improved with Ca addition due to the decrease of tetragonality and ease of 90° domain rotation. Charge piezoelectric coefficients in porous films are close to those of PCT ceramics of the same composition. These results, combined with the low dielectric constant, make PCT films an attractive material for microelectromechanical applications. © 1998 American Institute of Physics.
Show PACS
77.55.-g Dielectric thin films
77.65.Bn Piezoelectric and electrostrictive constants
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
77.22.Ch Permittivity (dielectric function)
61.72.Cc Kinetics of defect formation and annealing
81.15.Lm Liquid phase epitaxy; deposition from liquid phases (melts, solutions, and surface layers on liquids)

Asymmetric electro-optical switching of a nematic cell controlled by a corona poled ferroelectric polymer layer

L. M. Blinov, S. P. Palto, S. V. Yakovlev, and D. G. Sikharulidze

Appl. Phys. Lett. 72, 3377 (1998); http://dx.doi.org/10.1063/1.121609 (3 pages) | Cited 13 times

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A polar asymmetry of electro-optical behavior has been studied for a liquid-crystal cell, one electrode of which is covered by a thin film of a ferroelectric polymer. A well-known copolymer PVF2–TrFE (70:30) previously poled by a corona discharge has been used to modify the quadratic electro-optical response of the nematic mixture in a hybrid cell. The voltage for the onset of switching becomes polarity dependent. A simple model of an internal electric field created by a poled ferroelectric and built in the nematic layer is discussed, which is consistent with the sign and general features of the effect. © 1998 American Institute of Physics.
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42.79.Kr Display devices, liquid-crystal devices
42.79.Ta Optical computers, logic elements, interconnects, switches; neural networks
77.55.-g Dielectric thin films
77.80.-e Ferroelectricity and antiferroelectricity
77.84.Jd Polymers; organic compounds
77.84.Nh Liquids, emulsions, and suspensions; liquid crystals

Built-in voltages and asymmetric polarization switching in Pb(Zr,Ti)O3 thin film capacitors

J. Lee, C. H. Choi, B. H. Park, T. W. Noh, and J. K. Lee

Appl. Phys. Lett. 72, 3380 (1998); http://dx.doi.org/10.1063/1.121610 (3 pages) | Cited 47 times

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Asymmetric polarization switching of Pb(Zr,Ti)O3 (PZT) thin films with different electrode configuration has been studied in (La,Sr)CoO3/Pb(Zr,Ti)O3/(La,Sr)CoO3 (LSCO) heterostructures in which the conducting oxide (La,Sr)CoO3 and/or LaCoO3 (LCO) have been used as an electrode. Polarization-voltage (P-V) hysteresis loop of LSCO/PZT/LSCO was symmetric. However, LCO/PZT/LSCO showed a largely asymmetric P-V hysteresis loop and large relaxation of the remanent polarization at the negatively poled state, eventually leading to an imprint failure. On the other hand, LSCO/PZT/LCO exhibited large relaxation of the positively poled state. The asymmetric behavior of the polarized states implies the presence of an internal electric field inside the PZT layer. It is suggested that the internal electric field is caused by built-in voltages at LCO/PZT and LSCO/PZT interfaces. The built-in voltages at LCO/PZT and LSCO/PZT interfaces were 0.6 V and 0.12 V, respectively. © 1998 American Institute of Physics.
Show PACS
84.32.Tt Capacitors
85.50.-n Dielectric, ferroelectric, and piezoelectric devices
77.80.Fm Switching phenomena
77.22.Ej Polarization and depolarization
77.22.Gm Dielectric loss and relaxation
77.80.Dj Domain structure; hysteresis
77.55.-g Dielectric thin films
77.84.Ek Niobates and tantalates
77.84.Cg PZT ceramics and other titanates
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