摘要:

We present Monte Carlo results for switching in two and three dimensional Ising models in order to compare with classical nucleation theory. For the case of step-function voltage pulses classical nucleation theory correctly predicts the Monte Carlo results including a cross-over from a thermal nucleation to heterogeneous nucleation due to quenched defects. For triangular wave voltage pulses the coercive field depends on the sweep rate logarithmically roughly as predicted by classical nucleation theory. However the power law dependence on the logarithm of the sweep rate is significantly different from the classical nucleation theory prediction.

ISSN:1058-4587    

DOI:10.1080/10584589408018665

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The traditional rotating reflector antenna associated with airport traffic control systems is being replaced in some applications by a new design concept called the phased array. Generally planar in shape, it is made up of thousands of closely spaced, individual radiators whose composite beam can be shaped and spacially directed in microseconds, enabling it to track a multitude of targets at one time. This is accomplished electronically by RF phase shifters associated with each individual radiating element. No moving parts are required. State of the art, passive phased array antennas are limited in their application by cost, more than any other factor. Even utilizing the latest technology and fabricating techniques, the required phase shifters are not cheap, and with a typical array requiring thousands of individual antenna elements, each with its own phase shifter, the price of the total system quickly becomes prohibitive.

ISSN:1058-4587    

DOI:10.1080/10584589408018666

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We describe a monolithic phase shifter which combines the low loss of high temperature superconductivity (HTS) with the variable dielectric properties of a ferroelectric material SrTiO3. Phase shifts greater than 28 degrees per wavelength were observed around 30 K. Benefits of the combination of HTS and ferroelectric materials are described. The compatibility of YBa2Cu3O7-xand other ferroelectric materials is discussed.

ISSN:1058-4587    

DOI:10.1080/10584589408018667

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

We review several issues affecting the signal delivered to a sense-amp in high density ferroelectric nonvolatile memories. Typical DRAM parameters are used to approximate the expected signal and to determine constraints on ferroelectric properties. These calculations pertain to memories which are destructively read and which use either a 1T/1C (one cell per bit) or a 2T/2C (two cells per bit) architecture.

ISSN:1058-4587    

DOI:10.1080/10584589408018668

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In order to gain insight into the degradation mechanisms associated with ferroelectric thin films, such as fatigue and imprint, an understanding of the defect chemistry and transport properties of the material is needed. In this study several complimentary techniques have been used to either measure or calculate indirectly the various thermodynamic parameters governing defect formation and transport in Pb(Zr1/2Ti1/2)O3, (PZT). By combining the results of DC equilibrium conductivity, thermoelectric power and the sealed cell techniques, “constant composition oxygen activity” and “constant composition conductivity,” values for the oxidation enthalpy (ΔHox), hole trapping energy (EA) and the enthalpy of motion for holes (ΔEA) have been determined to be −0.49 eV, ≤0.9 eV and ≥0.1 eV, respectively. From these results, it is apparent that PZT is an oxygen excessp-type semiconductor in the experimental regime of 500°–700°C and P(O2) ≥ 10−4atm. Furthermore, the results indicate that there is a significant concentration of trapped holes at high temperatures and hole conduction appears to be an activated process (i.e. small polaron conduction).

ISSN:1058-4587    

DOI:10.1080/10584589408018669

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Plasma-enhanced chemical vapor deposition (PECVD) of doped and undoped silicon dioxide layers is widely used throughout the semiconductor industry for the passivation of processed devices before the final metallization processing steps. However, a reduction in the remanent polarization of PZT platinum-electrode capacitors has been observed when the capacitors were passivated with PECVD silicon dioxide films. This paper presents the results of a study to determine the effects of a standard PECVD silicon dioxide process on the retained polarization of Sol-Gel derived PZT capacitors with platinum electrodes. The retained polarization of the capacitors was measured before and after the silicon dioxide depositions. Measurements indicate that for PZT capacitors with temperature-stabilized top electrodes, there is relatively little change in the retained polarization after the depositions. However, for the PZT capacitors without the temperature-stabilized top electrodes, reductions in excess of 70% in the retained polarization can occur.

ISSN:1058-4587    

DOI:10.1080/10584589408018670

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The use of ceramic thin films as decoupling capacitors offers the possibility of capacitor integration within the integrated circuit (IC) package, and potentially, directly onto the IC itself. Since these configurations minimize series inductance, higher operational speeds are possible. In the present study we have investigated the dielectric and leakage characteristics of sol-gel PZT films. For compositions near the morphotropic phase boundary, dielectric constants of 1000, and loss tangents of about 0.02, were observed. The current-voltage behavior of the capacitors was characterized by a non-linear response, and significant asymmetry in both the leakage and breakdown characteristics as a function of bias sign was observed. Breakdown fields for PZT 53/47 thin films were typically ∼800 kV/cm at 25°C. We have also studied the effects of La and Nb dopant additions and alternate firing strategies on film leakage characteristics. Donor doping at 2–5 mol% lowered leakage currents by a factor of 103For films prepared by a multilayering approach, firing each layer to crystallization resulted in leakage currents that were a factor of 102lower than films prepared by the standard process.

ISSN:1058-4587    

DOI:10.1080/10584589408018671

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Large arrays of bolometer elements offer uncooled and simple operation, and a thermal imaging performance which challenges the cooled semiconductor (photon) detectors. A hybrid array technology, exploiting the pyroelectric property of ferroelectric ceramic materials in the bolometer elements, is the basis of a successful range of linear and 2-D arrays. However, other technologies will compete for cost effectiveness in large area devices. Direct integration of ferroelectric thin films onto suitable thermal microstructures on the silicon readout IC is attractive if deposition processes which are compatible with the silicon IC are established. Deposited lead based perovskite films show considerable potential. Thin film resistance bolometers will also compete, and have some advantages of compatibility in fabrication.

ISSN:1058-4587    

DOI:10.1080/10584589408018672

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

This paper reviews the rationale and the development environment for the nonvolatile memory technology(ies).

ISSN:1058-4587    

DOI:10.1080/10584589408018673

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor