摘要:

The ferroelectric properties of PZT on RuO2electrodes were compared to those on RuO2/Pt electrodes. The better hysteretic properties were obtained from Pt/RuO2/PZT/RuO2/Pt ferroelectric capacitors. The enhancement of ferroelectric properties is likely attributed to the modification in the microstructure of PZT film. The interfacial modification would be affected by the factors such as surface roughness, stress, and porosity of RuO2film. As the result of the interfacial modification, better quality PZT films are produced, thereby resulting in better ferroelectric properties. We made an effort to understand the relationship between the grain size and the coercive voltage in terms of the domain formation and the domain pinning in connection with defects like grain boundaries.

ISSN:1058-4587    

DOI:10.1080/10584589508012268

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Barium strontium titanate (BST) films have been fabricated using a modified sol gel method. The crystallization temperature was 100°C higher than that for lead zirconate titanate. The electrical properties improved when multiple rapid thermal processing was used. The dielectric constant of BST films was of the order of 250 which was characteristic of a small grain size and the presence of a low dielectric constant barrier. Doping by La, Nb, Mg, Y, Ru, Mn and Gd had an adverse effect on the dielectric constant even for small concentrations of about 1 at.%. Doping with cerium up to 3 at.% increased the dielectric constant of BST films up to 300 while dielectric losses remained low ≈ 0.025. The leakage current densities improved for donor type doping and were < 10 nA/cm2at E=60 kV/cm. BST films 1900 Å thick doped with 3 at.% of Ce had a charge storage density and capacitance density of 50 fC/μm2and 15 fF/μm2respectively.

ISSN:1058-4587    

DOI:10.1080/10584589508012269

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The influence of substrate materials on the crystallization kinetics of thin film PZT is presented. Structure and orientation of electrodes affect the nucleation and growth processes of PZT as it transforms from pyrochlore to perovskite. These determine the final film structure and ferroelectric and dielectric properties. Rapid thermal processed sol gel PZT was fabricated on ruthenium oxide (RuO2) and on platinum electrodes. A study of oriented RuO2electrodes was carried out using glancing angle XRD and transmission electron microscopy (TEM). These techniques were used to assess types and locations of phases present in the films, grain size, crystal orientation and morphology.

ISSN:1058-4587    

DOI:10.1080/10584589508012270

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

PZT films, especially PZT 53/47 films, have been intensively explored for a wide range of applications. A broad range of dopants can be incorporated fairly easily into PZT using sol-gel techniques, resulting in compositional tailoring of material properties. One important dopant is La, forming PLZT compositions which have a larger range of dielectric and ferroelectric properties than the PZT materials. To date, PLZT films have received less attention in electrical applications than PZT films in spite of the wider range of film properties achieveable with the former.

ISSN:1058-4587    

DOI:10.1080/10584589508012271

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It has been known that ferroelectric PZT thin films on RuOxelectrode exhibit relatively high leakage current level, while they show an outstanding fatigue property. When the PZT thin film is fabricated by sol-gel process over the RuOxlayer, the rosette structures are generally included on the surface of PZT film, which indicates that RuOxlayer does not offer an favorable environment for the nucleation of perovskite phase. A novel process completely eliminating the rosette structures on the surface of PZT film was accomplished in this work, with depositing thin seed PZT layer at the PZT/RuOxinterface by rapid thermal process (RTP). It was found that the obtained PZT films present very low leakage current level compared to the ordinary PZT/RuOxfilms with rosette structures. The main route of current leakage in PZT capacitor was also discussed.

ISSN:1058-4587    

DOI:10.1080/10584589508012272

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Polycrystalline thin films of SrTiO3—SrZrO3solid solutions were prepared along a new wet-chemical deposition route using β—diketone and propandiole as chelating agents. The structural properties of the films were studied by X-ray diffraction analysis, scanning and transmission electron microscopy. The thin film density was correlated with the permittivity using Maxwell's dispersion rule. The temperature coefficient of the capacitance as well as the dielectric losses were studied. Using transient impedance analysis, the dielectric relaxation, leakage, and resistance degradation of the thin films were investigated with respect to the Ti/Zr ratio.

ISSN:1058-4587    

DOI:10.1080/10584589508012273

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

PZT thin films up to 3000Å have been grown via a sol-gel route onto metallized sapphire substrates. Sharp X-ray peaks of perovskite indicating mixed or highly (111) oriented PZT were obtained and a link made to the thermal processing applied. Ferroelectric properties of these samples are discussed in light of development of a 4 kbit NVRAM demonstrator on SOS, which is also introduced. The relative merits of these properties along with endurance measurements are discussed with particular emphasis on the implications for complete integration with conventional SOS-based technology, in the context of non-volatile memory applications.

ISSN:1058-4587    

DOI:10.1080/10584589508012274

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Variations of remanent polarization and coercive field of undoped and yttrium doped Pb(Zr0.65Ti0.35)O3thin films prepared by Sol-Gel processing were observed using hysteresis measurement according to the cumulative switching cycles. Remanent polarization and coercive field of undoped Pb(Zr0.65Ti0.35)O3thin films after 1010polarization reversals were decreased and increased, respectively. But the variations of remanent polarization and coercive field of yttrium doped specimens with the polarization switching cycles were different from those of undoped specimens. In the case of yttrium doped specimens, remanent polarizations were not decreased and coercive fields were increased more than those of undoped specimens after fatigue. It was well known that doped yttrium reduced holes and increased vacancies in PZT thin films. This strongly suggests that the variations of holes and vacancies influence on the remanent polarizations and the coercive fields of Pb(Zr0.65Ti0.35)O3thin films after fatigue. Also, switching time was reduced as the yttrium doping increased.

ISSN:1058-4587    

DOI:10.1080/10584589508012275

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

A strong influence of ferroelectric polarization on d.c. conduction has been observed in PZT thin films with Pt electrodes. It is shown that the current-voltage response taken for measuring times of hundreds of seconds at room temperature is controlled by the crossover from the transient to steady-state conduction regime. In the transient regime the current flowing against the initial direction of the ferroelectric polarization is higher than that flowing in the reverse direction. In the steady-state regime a current asymmetry of the opposite sense is observed. At elevated temperatures (150–200°C) the asymmetry in both regimes is strongly suppressed. A Maxwell-Wagner relaxation model with ferroelectric and non-ferroelectric capacitors can qualitatively explain the observed phenomena.

ISSN:1058-4587    

DOI:10.1080/10584589508012276

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

It is well known that, for a given ferroelectric capacitor, the tilting of the hysteresis loops and the amount of remanent polarization measured in a ‘Sawyer Tower’ set-up are dependent on the sense capacitance (or load). However, it is less intuitive that a small sense capacitance will cause horizontal loop shifts and that these shifts depend on the state of the ferroelectric capacitor before the measurement. Since typical ferroelectric non-volatile memories operate with small sense-to-bit capacitance ratios, it is important to have models that can predict such effects. Complicated experimentation is necessary to implement the load and initial state effects properly in a load-line model. In contrast, the numerical ferroelectric capacitor model does not require any special experimentation to predict such effects. Experimental results from SrBi2Ta2O9are compared with both models.

ISSN:1058-4587    

DOI:10.1080/10584589508012277

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor