摘要:

We have carried out fatigue, aging and retention studies of epitaxial ferroelectric PbZr0.2Ti0.8O3/YBa2Cu3O7heterostructures, grown by pulsed laser deposition. The capacitors show fatigue lifetime of better than 1010cycles. We find that the fatigue process is reversible by the application of a 2 second “pulsed poling” treatment at the fatigue voltage. These results suggest that the loss of switchable polarization with cycling is due to domain wall pinning; however, the role of space charge effects at the electrodefilm interfaces cannot be ruled out. Indeed, the overall fatigue performance may be controlled by a combination of these two factors. These heterostructures show excellent resistance to aging (extrapolated lifetime of better than 1011seconds and good logic state retention characteristics (1011seconds).

ISSN:1058-4587    

DOI:10.1080/10584589208215562

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Ferroelectric thin films are playing a growing role as key elements in variety of devices. For various techniques of ferroelectric thin film preparation, the sol-gel processing is one of the most promising. In comparison with different deposition techniques, we survey the intrinsic advantages and the recent improvements of the sol-gel processing. In this review paper, several interesting topics, including epitaxial growth and grain-orientation, symmetric and asymmetricP-Ehysteresis loops, heterojunction effect of the interface between film and substrate, to attest pyroelectricity of the films, electrooptic coefficients in poled and unpoled films, possibility of amorphous ferroelectrics, etc., are introduced.

ISSN:1058-4587    

DOI:10.1080/10584589208215563

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Films of PZT about 0.2 μm thick with the composition PbZr0.53Ti0.47O3were prepared using the metalloorganic decomposition (MOD) process. The amorphous films produced by pyrolysis at 350°C were annealed at 550, 575, 600 and 650°C for 10 minutes, 1 hour or 4 hours. Films annealed at temperatures below 550°C showed no ferroelectric behavior while others annealed above 650°C showed signs of loss of ferroelectric behavior. Most films demonstrated satisfactory ferroelectric properties such as low switching voltage and high polarization values. Some PZT films also demonstrated fatigue life-time of more than 109switching reversals. The performance of the films was dependent on the annealing time and temperature. It was found that films with better initial polarization values did not necessarily demonstrate better fatigue behavior. The causes of film degradation as a result of switching based on the pinning of domains at grain boundaries triggered by the migration of pores is discussed.

ISSN:1058-4587    

DOI:10.1080/10584589208215564

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Microstructure of PbZr0.53Ti0.47O3films about 0.2 μm thick was studied as a function of annealing temperature and time using TEM and SEM. The films were heat treated in the temperature range 550–650°C for times from 10 minutes to 4 hours. The features characterized were crystal structure of individual PZT particles, PZT grain size and shape, porosity, and grain boundaries. The films were prepared by the metallo-organic decomposition (MOD) process which produced films amorphous to x-rays after pyrolysis. A growth mechanism of PZT particles from the amorphous film is discussed. It was found that at mild annealing conditions (i.e., low temperature and short annealing times), agglomerates of microcrystallites of perovskite, and probably pyrochlore, were formed. As the temperature was increased, the microcrystallites grew into porous submicron perovskite single crystals. With excessive heating, intraparticle pores were found to migrate and became pinned at the grain boundaries, causing widening of boundaries which probably was responsible for the degradation in ferroelectric properties observed in such films. The dependence of ferroelectric and fatigue behaviors on grain orientation was also investigated. It was found that PZT films oriented in the [111] direction demonstrated better fatigue behavior but not necessarily higher polarizations.

ISSN:1058-4587    

DOI:10.1080/10584589208215565

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We have discovered an unusual form of optical bistability in hot-pressed ceramic PMN (PbMg0.3Nb0.5Ti0.1O3) in which the thermal focussing of laser light at very low power densities (<1 kW/cm2) oscillates between two metastable states. At low laser powersPthe phenomenon is highly aperiodic but extremely reproducible; the oscillation events occur at times tNempirically given by the equationtN= A/(P-PN), where the threshold powerPNfor theN-th switching event is found to beNPo, withPo= 45 mW [i.e., 3.6 W/cm2]. At higher laser power the switching events become periodic, ca. 8 Hz, and resemble the phenomenon reported by Vasnetsov in thin films of thermotropic liquids. One of the two metastable spatial light patterns is doughnut-shaped; the other resembles a Bessel function, with large intensity in the center. Therefore by setting a Si-diode detector in the center of the pattern, we can monitor the oscillation. The oscillation event times (or frequency) are strongly dependent upon convection from the sides of the PMN thermal lens. Therefore the device acts as an optical (“photonic”) sensor that is extremely acute to pressure and flow rate of the surrounding atmosphere. We have measured pressure changes of 10−2Torr and flow rate changes of 0.1 cu. ft/hr. (0.3 m/s) in air.

ISSN:1058-4587    

DOI:10.1080/10584589208215566

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The behavior of thin films in the PLZT system made using a recently developed metal acetate precursor technique was investigated with respect to microstructural and crystallographic development. Variations in film microstructure and phase continuity were dependent on substrate and film composition. The optical quality of Zr rich films deposited onto sapphire substrates was impaired by the formation of a pyrochlore phase leading to a discontinuous microstructure. Application of a PLT buffer layer was shown to significantly modify this situation, improving the potential viability of this fabrication method.

ISSN:1058-4587    

DOI:10.1080/10584589208215567

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A new electrode material made of nickel alloy has been developed that can be used in place of platinum electrodes, which have commonly been utilized in conjunction with PbTiO3and Pb(Zr, Ti)O3thin films. This alloy electrode is composed of nickel, chromium, iron and aluminium. When heated in an oxidation atmosphere, an alumina film layer is generated on the surface of the alloy that prevents the electrode from oxidizing and reacting with PbO. The remanent polarization of the PbTiO3film on the alloy electrode oriented in the (111) direction was 25 μC/cm2, a value which is approximately equal to that of ceramics. The breakdown strength of the film reached the relatively large value of 190 kV/cm at room temperature. In addition, the as-grown film was already polarized with a degree of polarization estimated to be half that of fully polarized bulk ceramics.

ISSN:1058-4587    

DOI:10.1080/10584589208215568

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Polycrystalline Pb(Zr0.5Ti0.5)O3thin films with good ferroelectric properties have been prepared by metallo-organic decomposition (MOD) process, using acetate-based precursors, and followed by two different kinds of annealing process, independently, including oven annealing and rapid thermal annealing (RTA). The experimental procedures were described for the films deposited on Pt-coated silicon substrates. There were distinct differences between oven annealing and RTA process, in terms of structures, morphologies, and electrical properties of the films. The films with RTA process showed denser and smoother surface, finer grain sizes, and much higher dielectric constant (1200–1400), remnant polarization of 30–35 μC/cm2and lower coercive field of 65–85 kv/cm in the entire annealing temperature range of this study. At an annealing temperature of 550°C, RTA processed films showed identical XRD patterns of perovskite phase and clear ferroelectricity; however, it was not possible to realize the perovskite structure and ferroelectricity in the films oven-annealed at that temperature. These acetate-derived PZT films with RTA process were reproducible, showed high quality in uniformity and homogeneity.

ISSN:1058-4587    

DOI:10.1080/10584589208215569

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The dielectric response of thin films of perovskite ferroelectrics fabricated on electrodes such as indium tin oxide is calculated as a function of frequency, film & barrier layer thickness, and dielectric constant using an equivalent circuit model based on properties of the bulk, the electrode and a series resistance. Using reasonable estimates of parameters it is shown that measurements of the dielectric constant and loss by conventional dielectric bridges can lead to results which vary in a complex fashion and which may bear little relation to the true dielectric properties of the film. In particular, observation of a Curie temperature in thin films can often be masked by circuit or electrode effects. Results are given in terms of direct frequency plots and as impedance spectra.

ISSN:1058-4587    

DOI:10.1080/10584589208215570

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The polarization switching processes of ferroelectric polycrystalline Sn2P2S6films on Al substrates were studied. The effect of full reverse spontaneous switching after the influence of a repolarizing pulse on the prepoled sample was investigated. This opens the way for making the ferroelectric memory devices with rapid nondestructive readout.

ISSN:1058-4587    

DOI:10.1080/10584589208215571

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor