Single-Crystal Ferroelectrics: Physical and Electronic Properties, Stephen Streiffer

1. Basic definitions

1.1 What is a ferroelectric

1.2 Temperature dependence: ferroelectric vs. paraelectric

1.3 Piezoelectricity: the effect of mechanical stress

1.4 Domains

2. Traditional applications of ferroelectrics

3. Prototype systems

4. Electrical resistivity: point defects and doping

5. Origin of dielectric tunability

6. Losses in single crystals

Bulk Ceramic Ferroelectric and Composites: Manufacture and Applications, Louise Sengupta

1. Key parameters and desired properties for bulk ferroelectrics

2. Microwave measurements

3. Engineering issues for manufacture of bulk material and circuits

4. Applications

4.1 Bulk Ceramics - Devices and Antennas

4.2 Thick Film- Devices and Antennas

5. Future Directions

5.1 Bulk, Thick Film and Thin Film R&D

5.2 Devices

5.3 Antennas

Thin-Film Ferroelectrics: Deposition Methods and Applications, Bob York
1. Comparison of thin films and bulk materials

2. Deposition technologies and fabrication issues

3. Integrated device design and fabrication

4. Low frequency and high-frequency measurements

5. Microwave circuit applications.

Application of Ferroelectrics in Military Systems, Dennis Webb

Devices based upon ferroelectric materials are attractive for a number of military applications, especially those which place a premium on high tuning speed, low power consumption, small size and light weight. Although improvement in ferroelectrics' figure-of-merit will enhance their overall utility, there are areas where even current materials can be competitive with the more conventional technologies. Examples include planar phase shifters where ohmic losses tend to dominate and electronic fine-tuning of filters or oscillators to correct for inadequate manufacturing tolerances. This talk will discuss the major military applications envisioned for ferroelectrics, review the state-of-the-art of competitive technologies and assess the ferroelectric material attributes needed to compete with these technologies.

Ka-Band Phase Shifters using Bulk BSTO composites, John Talvacchio & Salvador Talisa

1. Requirements of ferroelectric materials for operation in the Ka-Band range

2. Basic design considerations for Ka-Band phase shifters

3. Status of bulk materials and figure of merit

4. Basic measurements showing materials characterisctics to date

Electronically Scanned Lens Antennas, Dharmesh Patel

The ferroelectric lens is a novel phased array antenna. It uniquely incorporates bulk phase shifting using ferroelectric material to reduce the cost of the phased array. The array does not contain an individual phase shifter at each radiating element. This presentation will describe the ferroelectric lens concept and how it can be used as a low-cost phased array. The presentation will cover mainly the work done at X band (8-12 GHz); some preliminary results at C band (5-6 GHz) and Ka band (28-36 GHz) will also be presented. The experimental results show that in order to obtain 360o differential phase shift, the electromagnetic wave suffers about 1.5 dB of loss in the ferroelectric at X band; the loss is lower at C band and higher at Ka band. Antenna patterns of an interferometer demonstrating electronic beam scanning at 10 GHz will also be presented.

Application of Ferroelectrics in Communications, Jonathan Lynch

The enormous efforts currently underway to produce a low cost electronically scanned antenna (ESA) have produced a number of novel antenna architectures in the past few years, including the use of ferroelectric materials as RF phase shifters. Ferroelectrics offer many advantages over conventional ESA approaches, the most important being the ability to fabricate an enormous number of devices on a single substrate using straightforward inexpensive processing techniques. This talk will describe the types of antennas that will be required in both the civilian and military sectors in the next few years, and will describe how the use of ferroelectrics may significantly alter the fundamental design approach of scanning antennas.

Thin-film BST Phase Shifters and Multipliers, Amit Nagra

We will present progress in the development and optimization of BST thin-films specifically for microwave integrated circuits, using both MOCVD-grown and RF magnetron-sputtered films. The material optimization efforts have concentrated on achieving high tunability and simultaneous low loss, and also developing suitable electrode systems for circuit fabrication on silicon substrates. Progress in application of the materials to monolithic microwave integrated capacitors and phase-shifters circuits will be discussed, using sputtered films on Pt-coated silicon substrates. Frequency multiplication devices have also been fabricated. The circuit fabrication and monolithic process development presented numerous technical challenges that were overcome by a combination of growth optimization, electrode schemes, and device design. The achievements thus far were made possible by a unique teaming strategy involving materials scientists, growth specialists, and process engineers, and microwave circuit designers. While the progress has been compelling, there is significant room for improvement in both material and circuit performance, and we will highlight particular areas for further research.

BST Material for Satellite Communications, Dean Face & Jim McCambridge

1. Efforts to produce tunable dielectric layers suitable for tunable microwave devices at both cryogenic (e.g. notch filters) and room temperatures (e.g. phase shifters).

2. Deposition of thin epitaxial films of BaxSr1-xTiO3, CaxSr1-xTiO3 and others by RF magnetron sputtering on a number of lattice-matched 51 mm substrates.

3. Observed dielectric and microstructural properties of these films

4. Dependence of permittivity and loss on crystalline quality

5. Dependence of tunability on the strain.

Large-signal RF Applications of BST Varactors, Amir Mortazawi

1. Device requirements for RF and Microwave tunable matching circuits,voltage controlled oscillators and tunable filters.

2. Material Selection and Processing issues

3. Parallel plate capacitor measurements (dielectric constant and loss tangent)

4. Determination of Capacitance tunability as a function of RF signal amplitude for high power applications.

5. Nonlinear Characterization/IP3 measurement

Hybrid Ferroelectric/Superconducting Microwave Circuits, Robert Romanofsky

Recent progress in materials' processing and deposition techniques along with better modeling and novel circuit designs has resulted in thin film ferroelectric/superconductor and ferroelectric/metal components that rival the microwave performance of state-of-the-art counterparts. Not long ago a coupled microstripline phase shifter patterned on a YBa2Cu3O7-d/SrTiO3/LaAlO3 multilayer structure exhibited more than 400 degrees of contiguous phase shift with less than 5 dB of insertion loss at Ku-band when cooled to 77 K. A figure of merit around 100 deg/dB was ultimately achieved. Similar devices were constructed using BaxSr1-xTiO3 films and metal electrodes for room temperature operation. The best figure of merit thus far is about 70 deg/dB. It is unclear what role surface effects from different electrodes play in determining performance. The best switched-line MESFET phase shifters offer an insertion loss of perhaps 8 to 10 dB at these frequencies. An accurate theoretical model of the ferroelectric coupled line phase shifters based on a variational solution for line capacitance and well-known coupled line theory has been developed. Besides phase shifters a Ku-band voltage controlled oscillator based on a 3l ring resonator patterned over a 2 mm thick SrTiO3 film demonstrated a ª5 % tuning range at 40 K. Other components that are under development include tunable bandpass filters intended for cryogenic operation and tunable microstrip patch antennas. A prototype 16-element phased array radar, based on BaxSr1-xTiO3 films, for potential automotive collision warning applications will also be discussed. And, finally, a design for a new type of scanning phased array antenna called the "ferroelectric reflectaray" will be presented.

Ferroelectrics Combined with Ferrites, Steve Kirchoefer

Wideband tunable phase shifters are being developed using ferroelectric thin films for operation at room temperature. Our efforts have focused on pulsed-laser deposition of thin films of barium strontium titanate which are being optimized to simultaneously possess low dielectric loss tangent and reasonable modulation of the relative permittivity with an applied dc field. These films are used to fabricate wideband distributed transmission lines. Ferroelectric/ferrite material combinations are being developed in order to mitigate the deleterious effects of modifying the capacitance per unit length on the impedance match of the transmission line. The addition of a ferrite will make it possible to independently tune both the inductance per unit length and capacitance per unit length. In principle, this will permit tuning of the phase velocity while maintaining the transmission line characteristic impedance. Barium strontium titanate has been successfully deposited on YIG. Initial microwave measurements have indicated that both magnetic and electric tuning mechanisms are active and that the phase velocity can be tuned equally well by either magnetic or electric field. An equivalent differential phase shift can be achieved with a magnetic bias on the order of 100 Oersteds as has been achieved with an electric bias of 40 Volts.

Tunable Filters for Wireless Base Stations, Balam Willamsen

Turnkey systems using fixed frequency HTS filters and cryogenic LNAs have been developed are currently being deployed for use in existing military and commercial receiver front-ends. The incorporation of frequency agile elements, such as BST capacitors, into these systems will enable many new applications in military and commerical wireless communications systems. The key challenge is to introduce frequency-agility without having a negative impact on the Q or power handling which make HTS filtering desirable.

Ferroelectrics with Ferrites and High-temperature Superconductors, Alfredo Anderson, Dan Oates and Gerald Dionne

A number of groups have demonstrated miniature bandpass and band-reject fixed-frequency filters using high-transition-temperature superconductors that have very low loss and very sharp skirts. We are working to extend the utility of these filters by adding tunability to their other desirable properties. The bulk of the tunability is provided by the variation of the permeability of the ferrimagnetic substrate with an external magnetic field. Strontium titanate thin films, working in the paraelectric state, are used to modify the resonance frequency of each resonator and trim the response of the filter. We have achieved tunabilities of up to 10% for 1%-bandwidth bandpass filters operating at 10 GHz.