摘要:

Polarization-dependent steady photovoltaic currents were found in thin lead zirconate-titanate films on silicon substrate. In addition to a polarization-dependent current, there was a steady non-polarization-dependent background current. There were also transient photovoltaic currents that appeared once, in an initial response to illumination, after the remanent polarization is switched. For mercury arc illumination and a 0.25-μm-thick, sol gel process, 53/47 Zr/Ti ratio film, the polarization-dependent current was equal to 2.7 A/C per W/cm2.

ISSN:1058-4587    

DOI:10.1080/10584589208215727

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

ISSN:1058-4587    

DOI:10.1080/10584589208215726

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Lithium niobate optical waveguides were fabricated on (110), and (100) sapphire by both diode and magnetron rf sputtering at 500-600°C in a flowing Ar/O2 atmosphere. Light coupling utilizing a rutile prism coupler was demonstrated. The propagation losses were obtained by measuring the scattered light from the surface using a fiber probe. The mode angles were also measured and used to calculate the thickness and the refractive indices of each sample. X-ray diffraction studies and the birefringence observed in the films have confirmed the crystalline nature of the films. The lowest value of attenuation of the He-Ne laser light propagating in the lithium niobate waveguide sputtered on sapphire was determined to be 1.1 ± 0.1 dB/cm. In addition, the lowest attenuation in lithium niobate thin film waveguides sputtered on SiO2/Si substrates was measured to be 2.3 dB/cm using end-fire coupling and fiber probing techniques.

ISSN:1058-4587    

DOI:10.1080/10584589208215728

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The mechanism of the dc electrical conduction and breakdown of perovskite-type titanates was investigated by impedance analysis. Based on an acceptor doped SrTiO3 model material, samples of different microstructures-ceramics, single crystals, and thin films-were employed. This approach allows us to distinguish conduction contributions of the bulk lattice, grain boundaries, and electrode interfaces. Based on defect chemistry studies, a predominant ionic contribution due to mobile oxygen vacancies and an additional p-type conduction were revealed for the bulk. At interfaces, space charge depletion layers of 100-500 nm width are formed in which the local conductivity is reduced by approx. four orders of magnitude compared to the bulk. Thin films show a similar depression of the conductivity. The combination of these facts may be indicative for considering thin films as distributed Schottky barriers. The field enhancement of the conductivity of thin films and of the interface depletion layers is compared and discussed.

ISSN:1058-4587    

DOI:10.1080/10584589208215729

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Theoretical aspects of polarization reversals in ferroelectrics will be reviewed, with the emphases placed on the application of the Kolmogorov-Avrami theory and of a lattice model which the author has proposed.

ISSN:1058-4587    

DOI:10.1080/10584589208215730

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

On the base of comparison of domain dynamics and transient current the applicability of Kolmogorov's model for the description of current shape in real ferroelectrics is considered. The influence of electrode edges and inhomogeneity of real samples are taken into account. The computer modeling of switching process is carried out. The obtained results can be applied for the improvement of the description the change of parameters in Ferroelectric memory devices.

ISSN:1058-4587    

DOI:10.1080/10584589208215731

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The numerical analyses of fundamental ferroelectric characteristics for memory use have been carried out by using a one-dimensional model of polarization reversal in ferroelectrics, in which latent nuclei are distributed randomly. Studied characteristics include pulse response, hysteresis (P-e curves), and switching current versus voltage (i-v curves) in ferroelectrics. Obtained results have been discussed.

ISSN:1058-4587    

DOI:10.1080/10584589208215732

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Advances have been made in the electronic characterization and analysis of thin-film ferroelectric (FE) memory capacitors using capacitance vs. voltage (C-V) measurements. A mathematical model of the small-signal electrical behavior of the FE capacitor has been developed. This analysis shows that the small-signal characteristics of the FE capacitor are largely determined by the space charge concentrations at the ferroelectric to contact interface. These space charge regions have an adverse effect on the permittivity, coercivity and switching characteristics of the ferroelectric capacitor. These results will contribute to improving ferroelectric processing, appraising the quality of ferroelectric devices, and developing device models of the ferroelectric memory capacitors for use in circuit design.

ISSN:1058-4587    

DOI:10.1080/10584589208215733

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We report a method using SEM, EDX, SIMS, and polarization-voltage hysteresis data to investigate changes that occur in PZT thin films fatigued using low (below 100 kHz) frequency square waves. Fatigue in PZT capacitors can limit the lifetime of destructive readout ferroelectric memories. Identification of physical and electronic changes that occur during fatigue will lead to understanding fatigue mechanisms and the development of improved electrode-ferroelectric interfaces.

ISSN:1058-4587    

DOI:10.1080/10584589208215734

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Discrepancies in switched polarization values obtained with pulse measurements and hysteresis measurements have been observed in ferroelectric PZT thin film capacitors. We attribute the differences as partially due to the effects of rapid depolarization. To measure rapid depolarization a pulse was applied to pole a ferroelectric capacitor; and then a second identical pulse of the same polarity was applied after a specified time. Significant switched charge was observed after the second pulse. This depolarization was observed to occur in the time frame from microseconds to seconds.Secondly, the effect of cycling voltage on fatigue was studied on several samples processed by different vendors. A strong dependence on voltage was obtained for one sample which was characterized using a voltage activation approach. A second sample showed no appreciable effect of cycling voltage on fatigue. The difference in behavior demonstrates that the dependence of the fatigue mechanism on voltage can vary significantly depending on the sample.

ISSN:1058-4587    

DOI:10.1080/10584589208215735

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor