Asymmetric Electrode Structure Research Articles

Influence of Asymmetric Oxide Electrode Structures on the Interface Capacity and the Failure Mechanisms in PZT Thin Films

The influence of symmetric and asymmetric electrodes including SRO and IrO2 within the electrode structure on the imprint and fatigue behavior in sputtered and CSD derived PbZrxTi1 − xO2 (PZT) thin films is investigated. It is found that SRO buffer layers are needed within top and bottom electrode to improve the fatigue behavior. However, for improvement of the imprint behavior, only one SRO buffer layer within either top or bottom electrode is sufficient, whereas IrO2 reveals no improvement of the imprint behavior. Furthermore the direction dependence of the imprint behavior is examined. To examine the influence of the interface capacity on the fatigue mechanism in more detail, the capacity is measured for different PZT film thicknesses during fatigue treatment. It is shown that there is hardly any difference in interface capacity during fatigue.

Molecular Orientation States and Optical Properties of Liquid Crystal Microlenses with an Asymmetric Electrode Structure

Liquid crystal (LC) microlenses are prepared using a pair of substrates with an asymmetric hole-patterned electrode structure. Their molecular orientation states and optical properties are studied by a simulation using the three-dimensional finite difference method (3D-FDM), and are also experimentally confirmed. It is found that a retardation distribution including two lens profiles for the center and outer regions of the hole-pattern is formed by the asymmetric electrode structure of the LC microlens. Focusing properties obtained in the experiments mainly correspond to those at the center region of the hole-pattern calculated by the molecular orientation simulation. Lens power can be improved and a bifocal lens can be achieved by using the asymmetric electrode structure and optimizing the combination of the hole-pattern diameters in the LC microlens.

Effect of thickness and upper electrode diameter on polarization switching and electron emission of Pb(Zr0.8Ti0.2)O3 ferroelectric cathode

To investigate the structural effect on the ferroelectric electron emission, the electric field distribution in a two-dimensional structure was calculated as a function of thickness and upper electrode diameter, and the switching charge density and emission charge were measured simultaneously. The simulation results of the electric field distribution showed that an asymmetric electrode structure caused a stray field on the bare surface of the ferroelectric cathode near the edge of upper electrode. The distance of the stray field from the electrode edge increased with increasing ferroelectric thickness, but it did not depend on the upper electrode diameter. The switching charge density increased more on the cathode with thicker ferroelectric and smaller upper electrode diameter. This was attributed to the difference of field distribution on the bare ferroelectric surface near the electrode edge. The expanded stray field for the thicker ferroelectric cathode enhanced polarization switching near the electrode edge. As a result, with increasing ferroelectric thickness, the emission charge increased and the threshold field decreased. However, there was no apparent difference between the emission charges from the different upper electrode diameters.

Pb(Zr0.8Ti0.2)O3강유전 음극에서 비대칭 전극구조가 전자 방출 특성에 미치는 영향

Pb(Zr_0.8Ti_0.2)O₃강유전 음극에서 비대칭 전극구조가 전자 방출 특성에 미치는 영향

Second Order Optical Nonlinearity of Polymers Induced by Charge Injection Asymmetry

Abstract A new mechanism for inducing bulk asymmetry and second order optical nonlinearity in polymer-dye systems is described. An anisotropic distribution of charges is established inside the medium resulting from the application of high voltage via an asymmetric electrode structure. The nonlinearity induced via this mechanism is perpendicular to the externally applied electric field. It is proven that the nonlinearity induced by charge injection cannot arise from dipolar alignment of molecules, but rather results from the nonlinearity of charged dye dimers in a bulk charge gradient.

Optical Performance of Liquid Crystal Cells with Asymmetric Slit-Patterned Electrodes in Various Applied Field Configurations

The performance of liquid crystal (LC) cells with asymmetric slit-patterned electrode structures in various applied field configurations is studied in detail, by measuring the interference fringe patterns and simulating the two-dimensional director distributions of liquid crystal by a finite element method (FEM). We investigate the molecular orientation effects in inhomogeneous electric fields and the optical properties of these cells as cylindrical microlenses, and show that disclinations, which deteriorate the lens properties, can be eliminated by adopting an appropriate applied field configuration.

Coupled model analysis of SAW floating electrode type unidirectional transducers

The performance of a single-phase unidirectional transducers utilizing the internal reflections of floating electrodes of electrically open and shorted metal strips within an interdigital electrode structure (FEUDT: floating electrode unidirectional transducer) is analyzed using a coupled-mode theory. All four independent parameters (the self and mutual coupling coefficient, the transduction coefficient, and the static capacitance) governing the coupling-mode equation with an electrical transduction term are analytically derived using extended Legendre polynomial expansions of electrical fields and perturbation analysis. Frequency response of radiation admittance and insertion loss, and SAW field distributions in a transducer are calculated from simple closed-form solutions of the coupled-mode equation. The shift effect of reflection and transduction centers due to the asymmetric electrode structure is clarified. Experimental results are given for test devices fabricated on a 128 degrees C YX LiNbO(3) substrate and compared with theoretical results.

Memory Effects in Nematic Liquid Crystals by a Surface Molecular Reorientation

A liquid crystal cell with an asymmetric electrode structure is prepared by using a slit-patterned or a hole-patterned electrode and an unpatterned counterelectrode. Only the surface of the latter substrate is treated by rubbing. When the liquid crystal cell is once heated up to an isotropic phase and then cooled down to a nematic phase with a sufficiently high electric field, a memory effect of the molecular orientation along a lateral component of a nonuniform electric field, which is produced by the patterned electrode structure, is observed after removing the electric field. This memory state can be erased by heating the cell up to the isotropic phase and it can be reproduced repeatedly. These phenomena are discussed in terms of the molecular orientation effects on the surface of an alignment layer without rubbing treatment.

Optical Properties of a Hybrid-Aligned Liquid Crystal Microlens

Abstract Microlens effects have been obtained in homogeneously aligned liquid crystal cells prepared using a hole-patterned electrode and a plane electrode. In the asymmetric electrode structure, an axially symmetric non-uniform electric field is produced and a radial distribution of refractive indices can be obtained by the molecular orientation effects in the non-uniform electric field. However, a disclination line which makes the optical properties worse is observed in the homogeneously aligned microlens when a voltage is applied across the cell. In order to improve the lens properties, hybrid-aligned liquid crystal microlens cells are prepared. Their optical properties are investigated and discussed in terms of a molecular orientation model in the non-uniform electric field of the hybrid-aligned cell.

A liquid crystal microlens obtained with a non-uniform electric field

Abstract A homogeneously aligned nematic liquid crystal cell with a hole-patterned electrode and with an indium-tin oxide (ITO-) coated counter-electrode has been prepared. A non-uniform electric field can be produced by the asymmetrical electrode structure. The liquid crystal director can be reoriented by applying a voltage across the electrodes, and this produces an axially symmetrical profile of the refractive index. This liquid crystal cell is expected to have a lens effect and so its optical properties have been investigated. The profile of the output light intensity was measured by using a detecting system with an optical fibre. Some relationships between the lens properties, the diameter of the hole and the thickness of the liquid crystal layer have been examined. The liquid crystal cell becomes a convex (converging) lens with a relatively low voltage. A focal length of several millimetres can be obtained by applying voltages of 3-4 V. As the applied voltage increases, the focal length becomes longer, and the cell changes to a concave (diverging) lens when a high voltage is applied (≳ 20 V). These properties are discussed from the viewpoint of the director orientation effects resulting from the non-uniform electric fields in the cell.