摘要:

Doping lead zirconate titanate (PZT) has often been examined in order to investigate changes in the electrical behavior of thin film ferroelectric capacitors.1In this study, PZT has been doped with Hf, Nb, and Zn. After reviewing the results of the initial studies, Zn doping of PZT was further investigated. Physical and electrical studies of Zn doped PZT have been conducted. These studies include x-ray diffraction analysis, hysteresis, pulsed switching, fatigue and retention measurements. Endurance measurements indicate an anomalous fatigue behavior of some Zn doped PZT thin film capacitors.

ISSN:1058-4587    

DOI:10.1080/10584589308216684

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The extensive work carried out at Caswell in recent years on ferroelectric ceramics for pyroelectric applications is reviewed briefly. With the ultimate aim of fully CMOS compatible integrated thermal detectors and imagers, pure and lanthanum doped lead titanate thin films have been deposited using the emerging PVD technique of dual ion beam sputtering (DIBS). The DIBS process produces high quality orientated perovskite films. Films have been formed at 500–600°C onto sapphire, MgO and silicon substrates by sputtering from an adjustable composite PLZT ceramic/Ti and Pb metallic target. Some substrates were coated with platinum/titanium prior to deposition to allow longitudinal electrical measurements to be made on the films. On silicon, the platinum/titanium electrodes were found to blister during the PLZT thin film deposition process. Pure and 7% lanthanum doped lead titanate films have shown pyroelectric effects with coefficients in the range 0.5–4.0 × 10−4Cm−2K−1and a figure of merit of 2.6 × 10−5Pa−0.5These results are encouraging with respect to the goal of integrated pyroelectric IR detector arrays on silicon. Further improvements should be possible since the process and substrate/electrode preparation have not yet been fully optimised.

ISSN:1058-4587    

DOI:10.1080/10584589308216685

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

In digital memory applications, metal ferroelectric metal (MFM) capacitors are typically fully switched from one polarization state to the other, with the difference in displacement current allowing determination of the cell state. However, by applying a pulse of insufficient amplitude and/or duration to fully switch the ferroelectric, such a device may be partially polarized. Here, the measurement of partial switching in sol-gel derived PZT MFM capacitors due to applied voltage pulses is reported. SPICE, a commonly used circuit simulation program, has been modified to incorporate a ferroelectric capacitor device model. The MFM device model added to SPICE is reviewed, and the simulation of partial switching is demonstrated. Simulation results modeling the PE hysteresis loops and switching transients due to applied voltage steps closely match those measured in the laboratory. We conclude with the modeling of incomplete switching due to applied pulses of insufficient amplitude to cause polarization saturation, which is attributed to the polycrystalline nature of the thin-films.

ISSN:1058-4587    

DOI:10.1080/10584589308216686

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Platinum and ruthenium oxide (RuO2) deposited by ion beam sputter-deposition are evaluated for use as electrodes for PZT thin film capacitors. The effect of deposition temperature, film thickness, and the presence of oxygen on hillock formation in platinum is discussed. It is shown that the hillock density in Pt/Ti/SiO2/Si films can be significantly reduced by properly controlling the processing conditions and film thickness. Stress measurements correlate with the experimental observation that depositing thinner platinum films (<800 Å) is an effective means of reducing hillock formation. The use of an intermediate deposition temperature 200–250°C also helps minimize hillock formation. Diffusion of the Ti adhesion layer into and/or through the platinum was significantly reduced by replacing the Ti with a TiOxadhesion layer. RuO2electrodes are compared to Pt in terms of resistivity, surface morphology, microstructure and film orientation.

ISSN:1058-4587    

DOI:10.1080/10584589308216687

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The Deposition by Aqueous Acetate Solution (DAAS) technique has been developed for the preparation of thin films of Pb(Zr0.53Ti0.47)O3[PZT(53,47)] perovskites. This process, which employs titanium acetate, tends to establish a chemically bound network in the pre-annealed phase and facilitates the crystallization of ferroelectric lead perovskites at a relatively low temperature. The addition of surface wetting reagents and oxidants and the action of ultrasonic waves were shown to affect the crystallinity and film quality of PZT(53, 47) perovskites on Pt<111>/Ti/SiO2/Si<100> substrates. The band structure analysis of the FTIR spectrum is illustrated to be a simple way of monitoring the crystallization of PZT(53, 47) perovskites. Physical and electrical characterization of the resultant thin films were performed. The advantages of the DAAS process for fabricating thin ferroelectric films are examined.

ISSN:1058-4587    

DOI:10.1080/10584589308216688

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

The aging of dielectric, elastic and piezoelectric properties is caused by a reduction of the 90° domain wall mobility. Defect dipoles in the domains orient slowly in energetically preferred directions. The oriented defects increase the force constant for the reversible domain wall displacement by electric or elastic fields. Observations of fatigue in bulk materials are briefly discussed.

ISSN:1058-4587    

DOI:10.1080/10584589308216689

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

A theory of polarization reversals in finite system is developed on the basis of the Kolmogorov-Avrami model. The observed size dependence of the switching time, which looks very peculiar at a glance, seems to be well explained by the present theory.

ISSN:1058-4587    

DOI:10.1080/10584589308216690

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Both direct current (d.c.) and alternating current (a.c.) conductivity measurements were undertaken on lead zirconate titanate (PZT) films synthesized by laser ablation deposition. Direct current (I) displayed an initial time dependence of the form I ∝ t−γ(γ ∝ 0.5–1.0). The possible reasons for this time dependence are discussed. At lower temperatures, the a.c. electrical conductivity shows a frequency dependence of the form σ ∝ ω′ which is explained as electrical charge hopping. At higher temperatures, the d.c. component of electrical conductivity becomes dominant, and is accompanied by a strong low frequency dispersion of the dielectric constant. The results are compared to published data on conductivity in SrTiO3, and discussed in terms of the latest theories for dielectric response of materials.

ISSN:1058-4587    

DOI:10.1080/10584589308216691

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Electrochemical models of failure in oxide perovskite materials are reviewed. It is noted that oxygen vacancies are a common source of electrical degradation, fatigue, and ageing. Taking the behavior of oxygen vacancies into account, a semi-quantitative model for time dependent dielectric breakdown (TDDB) is proposed and a quantitative fatigue mechanism is discussed for ferroelectric thin films. Based on the fatigue theory, a recent improvement in fatigue of ferroelectric thin films is presented. Correlation between leakage current and fatigue is also presented.

ISSN:1058-4587    

DOI:10.1080/10584589308216692

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Ferroelectric ceramic lead magnesium niobate (PMN) exhibits bistability in its thermal focussing (Chenet al., Appl. Phys. Lett.60, 332 (1992)) which is very sensitive to laser power, specimen temperature, ambient pressure and flow rate of air past the specimen (Scott and Chen,Integrated Ferroelectrics1, 71 (1992)). Under adiabatic switching conditions as many as eight hysteretic multistability loops (transmission versus input power) are observed (Chen and Scott,Integrated Ferroelectrics3, 69 (1993). In the present work at higher input power densities (ca. 10 MW/m2, c.w.) we observe some period multiplication, in qualitative agreement with earlier work on gases (Nakatsukaet al., Phys. Rev. Lett.50, 109 (1983); Harrisonet al., Ibid.51, 562 (1983); Firth and Al-Saidi,Ibid.53, 258 (1984). However, our data do not manifest the required symptoms of Feigenbaum bifurcations (a stochastic rather than chaotic power spectrum evolves, and the successive lengths of control parameter between bifurcations are not Feigenbaum-like). The switching characteristics can be quantitatively described by a system of May-Leonard oscillators, whose principal characteristics is the exact geometric progression of successive switching events.

ISSN:1058-4587    

DOI:10.1080/10584589308216693

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor