摘要:

The science and technology of ferroelectric thin films has experienced an explosive development during the last ten years. Low-density non-volatile ferroelectric random access memories (NVFRAMs) are now incorporated in commercial products such as “smart cards”, while high permittivity capacitors are incorporated in cellular phones. However, substantial work is still needed to develop materials integration strategies for high-density memories. We have demonstrated that the implementation of complementaryin situcharacterization techniques is critical to understand film growth and interface processes, which play critical roles in film microstructures and properties.

ISSN:1058-4587    

DOI:10.1080/10584580008222216

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

MAPLE Direct Write or MAPLE DW is a new direct writing technique which combines some of the major positive advantages of laser induced forward transfer and matrix assisted pulsed laser evaporation (MAPLE). This novel laser driven direct writing technique has demonstrated the deposition of metal, ceramic, and polymer materials in air and at room temperature and with sub-10 micron resolution for active and passive prototype circuit elements on planar and nonplanar substrates. Here, we have used MAPLE DW to synthesize ferroelectric devices for tunable microwave device applications. For ferroelectrics and the other functional materials, MAPLE DW can be used to investigate directly the properties of powder materials as a function of grain size, doping, and processing technique. The best properties obtained for Ba0.5Sr0.5TiO3and BaTiO3films were dielectric constants of 40, with loss tangents of about 0.025 with ∽ 1% tuning.

ISSN:1058-4587    

DOI:10.1080/10584580008222217

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Methoxyethoxide complexes in 2-methoxyethanol were used to produce epitaxial thin films of SrBi2Nb2O9, SrBi2Ta2O9, BaBi2Nb2O9, and BaBi2Ta2O9on [100] oriented single-crystals of SrTiO3and LaAlO3. Films were prepared by spin coating substrates with alkoxide solutions and firing in air at 850 °C for 20 minutes. With the exception of BaBi2Ta2O9on LaAlO3, all of the films were the desiredc-axis oriented Aurivillius phase. Out-of-plane orientation was confirmed by -2 scans which showed only [002/] reflections, and in-plane orientation was determined by phi-scans about the [105] plane. Lattice constants and full-width at half-maximum (fwhm) values for both in-plane and out-of-plane reflections are reported.

ISSN:1058-4587    

DOI:10.1080/10584580008222218

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

As the cellular and PCS spectrum become increasingly crowded due to the presence of a greater number of subscribers, it will become even more important for handset and base station manufacturers to come up with ways to ensure reliable system performance. In the handsets, the use of tunable filters, along with lower phase noise tunable oscillators, among other things, can help achieve the desired increase in reliability and system performance. It is in these areas where frequency agile components may be best applied. Ferroelectric thin/thick film technology is making significant improvements in reducing dielectric loss and tuning voltage requirements. Thus their application to the development of commercially useful and practical frequency agile components is gaining. This paper will consider some of the potential areas in filtering and tunable oscillator design where ferroelectric materials may be used to an advantage in future generation handsets.

ISSN:1058-4587    

DOI:10.1080/10584580008222219

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

We report measurements of gold circuits fabricated on four BaxSr1-xTiO3ferroelectric films doped with 1% Mn grown on MgO substrates by laser ablation. Low frequency (1 MHz) measurements of σTand tanδ on interdigital capacitors are compared with high frequency measurements of phase shift and insertion loss on coupled microstrip phase shifters patterned onto the same films. The variation in temperature of both high and low frequency device parameters is compared. Annealed with amorphous buffer layer and unannealed films are compared. Room temperature figures of merit of phase shift per insertion loss of up to 58.4°/dB at 18 GHz and 400 V dc bias were measured.

ISSN:1058-4587    

DOI:10.1080/10584580008222220

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Excellent single crystal BaxSr1-xTiO3(BST) films were grown on LaAlO3substrates using the metal-organic chemical liquid deposition (MOCLD) method. Very low losses (tanδ ∽0.002-0.008) were measured from these films at 400 KHz. Biaxially oriented BST films were successfully grown on polycrystalline YIG substrates using both MOCLD and pulsed laser deposition methods with biaxially oriented MgO and YSZ buffer layers. The dielectric losses of the films range from 0.005 to 0.015 while 25% of dielectric constant change was observed with 40V bias voltage up to 10 MHz. Both the dissipation and dielectric constant of the films remained nearly constants over a wide temperature range (77 K to 380 K). A dual-tuning microwave coplanar phase shifter using a BST film grown on a MgO buffered polycrystalline YIG substrate was fabricated. A significant phase shift was observed in GHz frequency range when an electric bias or a magnetic field was applied to the device.

ISSN:1058-4587    

DOI:10.1080/10584580008222221

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

One of the critical design aspects in ferroelectric tunable microstrip filters is choosing the right bias configuration, for large tunability as well as to maintain the filter's passband characteristics. This work is based on strontium titanate (STO) ferroelectric thin-film based tunable microstrip filters for cryogenic temperature applications. Large tunability factors have been demonstrated in YBCO/STO/LAO two-layered microstrip filters when operated at or below 77 K. The effect of the dc electric field (primarily responsible for tuning) and critical design parameters such as the insertion loss, frequency tunability, return loss, and bandwidth of superconductor/ferroelectric/dielectric microstrip tunable K-band microwave filters is discussed in this work.

ISSN:1058-4587    

DOI:10.1080/10584580008222222

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The Brillouin and Raman scattering from a complex single crystal from the tungsten-bronze family, (K0.5Na0.5)0.2(Sr0.75Ba0.25)0.9Nb2O6doped with Cu2+(KNSBN:Cu), have been comparatively studied in a wide temperature range around the ferroelectric transition. Step-like anomalies in hypersonic velocity and damping confirm the first-order structural transition. These anomalies look like some perturbations on the high-temperature slopes of both a broad dip in sound velocity and a broad maximum in damping that develop in a wide temperature range. The acoustic behavior of KNSBN:Cu does not simply follow the Landau theory prediction valid for many ferroelectrics except relaxors, to which the KNSBN:Cu behavior is intrinsically analogous. The total intensity of the Raman spectra as well as the intensity of separate internal and external vibrations and their width correlate with acoustic anomalies, namely there are step-like drops at the same temperature of the first-order transition and a broad range where the intensity is drastically increased.

ISSN:1058-4587    

DOI:10.1080/10584580008222223

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

(La, Sr)CoO3/PbLa0.1TiO3/(La, Sr)CoO3tri-layers have been grownin situusing pulsed laser deposition on single crystal LiF and NaCl substrates because of their potential to serve as substrates and sacrificial layers for building suspended infrared detector structures. At growth temperatures around 525°C to 615°C and oxygen partial pressures of ∽25 mTorr, the LaSrCoO3/PbLaTiO3/LaSrCoO3tri-layers on LiF substrates exhibit preferential orientation, as indicated by x-ray diffraction data. The surface morphology of each successive layer is smooth, as shown in scanning electron microgram. Higher growth temperatures result in better orientations but suffer from substrate out-gassing, while lower growth temperatures lead to polycrystalline film growth. On the NaCl substrates, buffer layers, such as Pt and Pd, are necessary to achieve oriented films by suppressing severe substrate out-gassing at the growth conditions required for stoichiometric (La, Sr)CoO3/PbLa0.1TiO3/(La, Sr)CoO3tri-layer growth.

ISSN:1058-4587    

DOI:10.1080/10584580008222224

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Ferroelectric/dielectric materials are useful for a variety of different applications. Addition of small amounts of different dopants often dramatically improves the materials performance. The conventional approach to exploring new materials is to make and characterize samples of discrete composition one at a time. In an effort to accelerate this process, we fabricate a combinatorial materials chips containing 256 differently doped (Ba, Sr)TiO3thin films. From this study, we found that tungsten doping in this class of materials greatly reduces the dielectric loss and does not significantly affect the tunability of these materials. As the result, the overall figures of merit of the materials are greatly improved.

ISSN:1058-4587    

DOI:10.1080/10584580008222225

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor