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A current drawback of spintronics is the large power that is usually required for magnetic writing, in contrast with nanoelectronics, which relies on 'zero-current,' gate-controlled operations. Efforts have been made to control the spin-relaxation rate, the Curie temperature, or the magnetic anisotropy with a gate voltage, but these effects are usually small and volatile. We used ferroelectric tunnel junctions with ferromagnetic electrodes to demonstrate local, large, and nonvolatile control of carrier spin polarization by electrically switching ferroelectric polarization. Our results represent a giant type of interfacial magnetoelectric coupling and suggest a low-power approach for spin-based information control 10.1126/science.1184028

Unidirectional electric current flow, such as that round in a diode, is essential for modern electronics. It usually occurs at asymmetric interfaces such as p-n junctions or metal/semiconductor interfaces with Schottky barriers. We report on a diode effect associated with the direction of bulk electric polarization in BiFe[O.sub.3]: a ferroelectric with a small optical gap edge of ~2.2 electron volts. We found that bulk electric conduction in ferroelectric monodomain BiFe[O.sub.3] crystals is highly nonlinear and unidirectional. This diode effect switches its direction when the electric polarization is flipped by an external voltage. A substantial visible-light photovoltaic effect is observed in BiFe[O.sub.3] diode structures. These results should improve understanding of charge conduction mechanisms in leaky ferroelectrics and advance the design of switchable devices combining ferroelectric, electronic, and optical functionalities.

The domain dynamics and the evolution of the critical exponent [beta] in a ferroelectric relaxor system, strontium barium niobate (SBN), are examined. The crystals have undergone a phase transition, which is not in a uniform way with homogeneous polarization throughout the crystal.

The ferroelectric gate operation in the polyvinylidene difluoride (PVDF)/trifluorethylene (TrFE)/AlGaN/GaN system is shown and its retention is measured. The transport measurements in combination with piezoelectric scanning probe microscopy have described the physical origin of the retention loss in the system.

The dielectric relaxation and electrical conductivity behavior are studied in the ferroelectric ceramic/polymer composite ([Pb.sub.0.88][Sm.sub.0.88])([Ti.sub.0.99][Mn.sub.0.01])[O.sub.3]/polyetherketoneketone (PEKK). The relaxation process is associated to the decay of the polarization in the oxygen defect-related dipoles because of their hopping conduction.

Key integration technologies for 180-nm node ferroelectric memories are discussed. Findings reveal that the approach achieves peak-to-peak value of 675 mV in bit-line potential and a sensing margin of 300 mV in opposite-state retention.

The dielectric and piezoelectric responses of soft Pb[Zr.sub.x][Ti.sub.1-x][O.sub.3] (PZT) under combined electric and mechanical loadings are examined. The enhanced and reduced electromechanical responses are described by the 90 degree domain switching from which the electrical field and compressive stress take their roles at different times within a cycle.

A phase-lock loop (PLL) circuit utilizing a ferroelastic capacitor as the timing element within the voltage-controlled oscillator is presented. The PLL explored the timing characteristics of ferroelectric capacitors compared to linear capacitors and represents a new direction for creating low-jitter phase-locked loops.

Paraelectric BaSrTi[O.sub.3] films deposited by sol-gel have been investigated from 1 kHz to 40 GHz using coplanar waveguides, resonators, and inter-digitated capacitances. At room temperature and without bias, the dielectric constant [[epsilon].sub.[tau]] is around 300 and the loss tangent is 5 x [10.sup.-2] Tunability is 40% for a 40-V bias voltage. Analog phase-shifter circuits were subsequently fabricated in order to obtain a 360degrees] phase shift in the K[alpha]-band with a moderate bias voltage. The lowest bias value was 17 V at 40 GHz, whereas 40 V were necessary at 30 GHz. For the latter condition, the insertion loss was -6 dB. The best figure-of-merit of the phase shifters with a loading factor of 1.4 was 27[degree]/dB. These results show an improvement in terms of voltage-controlled tunability. Index Terms--Analog phase shifters, dielectric characterization, ferroelectric thin films, interdigitated capacitors, tunability.

This paper presents continuously variable 20- and 30-GHz ferroelectric 360[degree] phase shifters. A lumped-element all-pass network topology is used for the phase-shifter designs. The phase shifters are fabricated using barium-strontium-titanate (BST) capacitors as the tuning element. The BST thin films are epitaxially grown on sapphire substrates using the combustion chemical vapor deposition process, exhibiting low loss and high tunability. The 20-GHz phase shifter has a dimension of 0.95 x 1.32 x 0.5 mm.sup.3; its maximum phase shift occurs at 21.7 GHz, where the insertion loss varies from 6.1 to 3.9 dB and the return loss is from 15.2 to 4.7 dB. Measured figure-of-merit is 54[degrees]/dB using the highest insertion loss. The dimension of the 30-GHz phase shifter is 1 x 1.2 x 0.5 [mm.sup.3]. Measured insertion loss and return loss vary from 7.0 to 4.3 dB and from 29 to 4.8 dB, respectively, at a center frequency of 32 GHz. The figure-of-merit is 51[degrees]/dB. The dc bias required to tune the low-voltage phase shifters is 0-30 V. Typical third-order input intercept power ([IIP.sub.3]) of the phase shifters is greater than 30 dBm. Index Terms-Barium-strontium-titanate (BST), combustion chemical vapor deposition (CCVD), ferroelectric, K-band, K[alpha]-band, phase shifters.

A device architecture for improving the linearity of barium-strontium-titanate (BST) capacitors is proposed, analyzed, and experimentally demonstrated. The basic concept is to reduce the RF swing across the ferroelectric varactors by connecting multiple capacitors in series. With proper biasing networks, the overall device preserves its tunability. In this paper, the proposed architecture is analyzed to derive the equations that relate its quality factor and tuning speed to the design parameters. Parallel-plate BST capacitors are fabricated based on the architecture. Various measurements are performed to demonstrate the efficacy of the technique. The third-order intercept point at input ([IIP.sub.3]) is found to be improved by 16 dB. The hot-tuning test shows that the tunability is maintained for up to 20-V peak-to-peak swing. BST capacitors utilizing the proposed technique are used in a phase-shifter design. The 2.4-GHz phase shifter exhibits high [IIP.sub.3] greater than 40 dBm. Index Terms--Barium-strontium-titanate (BST), ferroelectric capacitor, linearity, phase shifter.

A tunable capacitor based on a ferroelectric thin film grown on a dielectric substrate is a promising component for reconfigurable and tunable devices for numerous RF and microwave applications such as phase shifters, tunable filters, and tunable matching networks. The goal of this paper is characterization of the insertion loss in a reflection-type microwave phase shifter based on the ferroelectric tunable capacitor. The reflection-type phase shifter based on ferroelectric planar tunable capacitor was designed, manufactured, and tested. Its simulated and measured insertaion loss and phase shift are compared. Two loss mechanisms in the phase shifter were distinguished: the loss in the tunable capacitor and the loss in the associated circuitry (metallization and substrate). The properly organized investigations of the dissipation of energy in metallization and dielectric substrate can result in a sufficient improvement of the quality of the devices. As a final result, one may anticipate that the figure-of-merit of a ferroelectric tunable or switchable phase shifter can reach 200 deg/dB. Index Terms--Ferroelectric tunable capacitor, figure-of-merit of phase shifter, reflection-type phase shifter.

Phase-shifter design based on ferroelectric materials technology has shown promising performance characteristics and the potential for achieving the long standing goal of realizing high performance, low-cost microwave phase shifters, and phased-array antennas. In this paper, we present a unifying spectral-domain approach and a newly derived Green's function that provide a 'first principles' method for the design and analysis of ferroelectric material based coplanar waveguide phase shifters. The modified Green's function not only accounts for the finite thickness of the conductors, but also for the 'current crowding' phenomena that results from using the very high dielectric constant ferroelectric film. Both isotropic and anisotropic effects were analyzed and the developed theoretical results were in excellent agreement with measured data. It is also shown that the multidielectric layer-based design of these phase shifters may provide nearly threefold increase in the figure-of-merit compared with the direct metallization case. A new biasing approach is proposed to achieve effective biasing of the ferroelectric layer and without excessive field concentration in the overlaying low dielectric layer. The formulation, procedure for the calculation of the current and charge distributions, and comparison between simulation and experimental results are described and presented in detail. Index Terms--Anisotropic, coplanar waveguide (CPW), ferroelectric, Green's function, phase shifter, spectral domain.

This paper evaluates the RF tuning and the microwave nonlinear response of SrTi[O.sub.3] thin films by measuring the third harmonics and third-order intermodulation (IMD) products of several coplanar waveguide transmission lines fabricated directly on SrTi[O.sub.3] thin-film samples. From these measurements, we obtained the distributed nonlinear capacitance per unit length as a function of RF bias voltage C([V.sub.rf]) using an accurate equivalent circuit to model the spurious signal generation. A unique value of C([V.rf]) is used to describe the third-harmonic generation at frequencies 3[f.sub.1] and 3[f.sub.2], and the IMD products at frequencies 2[f.sub.1] + [f.sub.2] and 2[f.sub.2] + [f.sub.1] , where [f.sub.1] and [f.sub.2] represent the fundamental frequencies of the two-tone excitation signal. We compare C([V.sub.rf]) with the distributed nonlinear capacitance measured as a function of the de-bias voltage C([V.sub.dc]) and obtain excellent agreement at 50 and 76 K. From these results, we conclude that full tunability can be achieved on nanosecond time scales, and that spurious signals generated in SrTi[O.sub.3] ferroelectric transmission lines at microwave frequencies can be modeled based on de-biased measurements. Index Terms--Ferroelectric thin films, frequency tuning, microwave measurements, nonlinear effects.

A tunable matching network (TMN) based on ferroelectric capacitors for cellular power-amplifier applications was designed, fabricated, and tested. When the matching network is operated for GSM850/900 frequency bands, the input impedance varied from 3.44--jl.87 to 3.55--j0.02 [ohm] with a power gain variation of -1.35 to -1.62 dB. When the circuit is operated for digital communication system/personal communication system/wideband code division multiple access frequency bands, the input impedance varied from 4.28--j0.06 to 4.31 + j0.97 [ohm] with a power gain variation of -2.05 to -1.79 dB. The nonlinearity of the TMN was also characterized on an on-wafer load-pull system using a 1.95-GHz test signal with CDMA2000 and high-speed downlink packet access modulation strings. Index Terms--Barium-strontium-titanate (BST), ferroelectric, output matching network, paraelectric, power amplifier (PA), tunable matching network (TMN), varactor.

A tunable third-order combline bandpass filter using thin-film barium-strontium-titanate varactors and fabricated on a sapphire substrate is reported. Application of 0-200-V bias varied the center frequency of the filter from 2.44 to 2.88 GHz (16% tuning) while achieving a 1-dB bandwidth of 400 MHz. The insertion loss varied from 5.1 dB at zero bias to 3.3 dB at full bias, while the return loss exceeded 13 dB over the range. The third-order intercept of the filter was found to be 41 dBm. Index Terms--Barium strontium titanate (BST), combline filter, ferroelectric films, intermodulation distortion, microstrip filters, resonators, thin-film devices, tunable filters, varactor.

Ion emission from ferroelectric plasma sources driven by radio frequency (RF) applied voltage is studied. An experimental investigation of particle emission from lead zirconate titanate ferroelectric ceramics driven by bursts of seven cycles of RF voltage at 248 kHz has revealed significant ion current emission. Measured electron to ion peak current ratios ranged from 11 to 19, which is much lower than the expected thermal current ratio. These results indicate that the ions are being preferentially accelerated. An analysis of the ponderomotive force on the ions and electrons reveals that it may be responsible for acceleration of the ions. The ferroelectric plasma is examined as a possible micropropulsion thruster. Performance estimates based on the ponderomotive acceleration calculations predict specific impulse of 2000-3000 s, thrust of 0.1-1 mN, and specific power of 15 W/mN. These estimates are compared to existing micropropulsion concepts, revealing the attractiveness of ferroelectric plasma sources. Index Terms--Ferroelectric devices, ion sources, plasma engines, space vehicle propulsion.

A study of a model of the quasi-Debye loss mechanism in SrTiO3 and Ba0.6Sr0.4TiO3 perovskite ferroelectrics at microwave frequencies is presented. The study concluded that the contribution of the quasi-Debye loss mechanism is large enough to affect the performance of tunable microwave devices based on SrTiO3 ferroelectrics materials.

A l ow thermal-budget process for fabricating a PZT capacitor is examined and reported.

Dynamic behavior of multilayered piezoelectric diaphragms is investigated and reported.

An innovative megnetostrictive and piezoelectric laminate composite design is described and discussed.

Ferroelectric swithing emission, dielectric switching emission, and pyroelectric emission are investigated and discussed.

We have developed a classroom experiment suitable for undergraduate students in which they fabricate a ferroelectric capacitor from potassium nitrate and then observe the electrical behavior as the film is cooled through its transition temperature. The experiment can be carried out using a capacitance bridge that is simple to construct and inexpensive. The experiment gives students a hands-on experience with ferroelectric phenomena, a subject of considerable interest from both a fundamental and a technological standpoint. [DOI: 10.1119/1.1561271]

Poling conditions and resulting polarization and piezoelectricity in relatively thick ferroelectric films and cable layers are investigated and reported.

An approach is proposed for extracting model parameters of High Temperature Superconductor (HTS) films from experimental characteristics of microwave resonators and filters.

A model is?presented that? describes the main characteristic nonlinear phenomena of ferroelectricity.

The presence of a space chargein a ferroelectric thin film, in the presence of Schottkey barriers at two electrode/film interfaces, are investigated. Numerical simulation, using Landau-Khalatnikov, theory, is employed.

The design and the finite-element analysis of a novel microstrip antenna suitable for low-frequency applications is presented. The patch is mounted on a double-layered substrate of ferroelectric and ferrimagnetic materials to lower the resonant frequencies. The media are accurately simulated, accounting, respectively, for their frequency-dependent and anisotropic behavior. Index Terms--Electromagnetic compatibility, FEM, ferrite, ferroelectric media, microstrip antennas.

A ferroelectric-based structure for an integrated microphone and microspeaker is described. The device is suitable for applications that require high-quality micro-acoustic devices.

As the search continues for low-cost and high-performance components for the front-end devices for wireless communications systems, some focus has been placed on exploring new and innovative designs based on ferroelectric technology. In this paper, we present new phase-shifter designs and an integrated phased-array antenna system based on the use of multilayer ferroelectric materials and the continuous transverse stub (CTS) technologies. Simulation results show that with the appropriate selection of the materials properties and the dimensions of the multilayer dielectric system, insertion losses may be reduced by as much as a factor of 100. These results also show that while only a slight reduction (15%) in the maximum achievable tunability was observed, it was possible to achieve significant improvement in impedance-matching characteristics. A procedure to enhance the radiation efficiency from an integrated ferroelectric/CTS phased antenna array design is described and specific array designs are discussed. Index Terms--Antenna array, continuous transverse stub, ferroelectric material, microstrip, multilayer dielectrics, phase shifter.

A method is proposed for measuring the dielectric constant, loss tangent, and tunability of ferroelectric thin films with on-wafer Through-Line-Reflect (TRL) calibration. Experimental results indicate that overall insertion loss is less than 3 dB/cm, even at frequencies as high as 20GHz.

Typical paraelectric materials (e.g., SrTi[O.sub.3], Kta[O.sub.3], [Ba.sub.x][Sr.sub.1-x]Ti[O.sub.3], x < 0.5) and electrically tunable microwave devices based on these materials are briefly reviewed. The analysis shows that in spite of the recent year's extensive efforts, no considerable improvement in the microwave losses in thin paraelectric films has been achieved. Thin films, regardless of fabrication method and substrate type, have much lower dielectric permittivity than bulk single crystals, and the loss tangent at microwave frequencies (f > 10 GHz) is of the order of 0.01 (at zero dc-bias field) at room temperature. Nevertheless, quite promising component and subsystem level devices are successfully demonstrated. Use of ceramic (bulk and thick film) ferroelectrics in tunable microwave devices, currently considered for industrial applications, offer cost reduction. In this paper, explicitly for the first time, we consider possibilities and benefits of using ferroelectrics in polar phase in electrically controllable microwave devices. Examples of using ferroelectrics in polar state (e.g., [Na.sub.0.5] [K.sub.0.5] Nb[O.sub.3], SrTi[O.sub.3] in antiferroelectric phase) in electrically tunable devices are reported. Index Terms--Ferroelectrics, paraelectrics, tunable microwave devices.

The effect of the imprint on the operation of ferroelectric random access memory (FeRAM) is estimated. A quansitheoretical model is used that includes the hysteresis shift along the voltage axis and the depolarization induced by the hysteresis shift.

Research describing electron cyclotron resonance ion sources is presented. In particular the effects of direct electron injection by means of a ferroelectric ceramic cathode are investigated.

A historical review of equivalent circuit modeling of acoustic structures is provided. PE (piezoelectric) and PM (piezomagnetic) crystal plates, of arbitrary anistropy, executing simple thickness motion, are discussed.

A new field-effect transistor (FET)-type memory cell with a one-transistor, and two-capacitor (1T2C) is described. Generation of depolarization field in ferroelectric film during data retention is suppressed by polarizing ferroelectric capacitors in opposite directions.

A new study investigates the piezoelectric and dielectric properties of PMN-PZT thin films prepared using the sol-gel method.

A new study investigates the anisotropic domain structure of KTiPO4 crystals reversed by low electric field.

The calculation of the optical and electronic properties of tetragonal BaTiO3 and cubic SrTiO3.

A study of the threshold hysteresis or memory window of a ferroelectric capacitor and a p-n diode is presented. Investigation shows a memory window width of 2.7V when observed by capacitance-voltage measurement.

Research describing the fabrication of strontium bismuth tantalate thin capacitor films is presented. In particular the phase formation and microstructure of the films is investigated.

Research describing the effects of lanthanum doping on barium-strontium-titanium thin films is presented. In particular improvements to insulating and dielectric properties with respect to undoped films are invetigated.

The development of a multilevel metal process-based ferroelectric memory technology is presented.

Research is presented concerning the use of a multilinear model for ferroelectric and ferroelastic properties of PZT ceramic to investigate the poling behavior of 1-3 composites of a polymer matrix in which PZT ceramic rods had been embedded.

Research is presented concerning the use of the Ginzburg-Landau phenomenological theory to investigate the sandwich structure (PbTiO3/BaTiO3/PbTiO3) of a ferroelectric system. Long-range coupling interactions are discussed.

Field forced ferroelectric to antiferroelectric phases in antiferroelectric PbZrO3 thin films were studied with regard to the backward switching phenomenon.

Ferroelectric cathodes made of perovskites, were studied for lifetime and emission characteristics.

Research is presented concerning the investigation of the performance of a compact, highly selective microstrip line bandstop filter consisting of YBa2Cu3O7-delta on a substrate of LaAlO3.