New Publications are available for Ferroelectric devices
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New Publications are available now online for this publication.
Please follow the links to view the publication.High frequency thin film ferroelectric acoustic resonators
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000646
Presently front-end RF filters are one of the largest elements in the PCS handset and it is very difficult to fabricate them on chip. To achieve component miniaturization and integration in future mobile communication systems, thin-film bulk acoustic resonators (FBAR) will be the best choice to replace the current ceramic or surface acoustic wave (SAW) devices because they are compact, have low-loss and are largely compatible with the existing high frequency Si/GaAs IC processing. An FBAR is a resonant piezoelectric device similar to the more familiar quartz resonators, which consists of piezoelectric layer sandwiched between two electrodes. (3 pages)Ferroelectrics, microsystems and nanotechnology
http://dl-live.theiet.org/content/conferences/10.1049/ic_20000682
Ferroelectric materials possess many useful properties which are widely exploited in electronic devices, from the pyroelectric infra-red detectors used in remote light switches and door openers through piezoelectric ceramics and single crystals used for sound generators and frequency stabilization/filtering SAW devices in mobile phones to high value chip-capacitors. These properties also make them useful materials for microsystem devices and in nanotechnology. In recent years, the ability to grow thin and more recently thick, films of ferroelectric oxides at relatively low temperatures has greatly increased their potential for use in novel micro-engineered devices. Examples are: low cost thermal imaging arrays using thin pyroelectric films deposited directly upon silicon chips for applications such as automotive and people sensing/monitoring devices; piezoelectric ultrasonic micro-motors and thin film bulk acoustic resonators for frequency control and filtering in mobile communications. In the field of nanotechnology, the SPM can now be used to manipulate domains in ferroelectric thin films on the scale of 200nm or less, bringing new possibilities in the field of high density information storage and other novel reconfigurable devices at the nanometre scale. The commercial exploitation of many of these devices and effects will depend upon the ability to grow good quality ferroelectric thin and thick films onto a range of substrates at low temperatures (ca. 500°C). (5 pages)Noise characteristics of an oscillator with a barium strontium titanate (BST) varactor
http://dl-live.theiet.org/content/journals/10.1049/ip-map_20050068
The phase noise of an oscillator with a thin-film barium strontium titanate (BST) capacitive tuning element, or varactor, is characterised and benchmarked against the same oscillator with a silicon semiconductor junction varactor. Phase noise tracks closely with varactor <i xmlns="http://pub2web.metastore.ingenta.com/ns/">Q</i> within a specific voltage range as expected. Compared to the semiconductor varactor-based oscillator, the BST-based oscillator demonstrates reduced phase noise degradation near zero volts, but greater phase noise degradation when operated near breakdown.High performance ferroelectric memory with grounded-plate PMOS-gate cell technology
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20030351
A new FRAM architecture utilising a grounded-plate PMOS-gate (GPPG) ferroelectric cell is proposed. A GPPG cell consists of a PMOS access transistor and a ferroelectric data storage capacitor. Its plate is grounded. The proposed architecture employs three novel methods for cell operation: a <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DD</sub>-precharged bit-line, a negative-voltage word-line technique and negative-pulse restoration. Because this configuration does not need the plate control circuitry, it greatly increases the memory cell efficiency. In addition, unlike other reported common-plate cells, this scheme can supply a sufficient voltage of <i xmlns="http://pub2web.metastore.ingenta.com/ns/">V</i><sub xmlns="http://pub2web.metastore.ingenta.com/ns/">DD</sub> to the ferroelectric capacitor while detecting and storing the polarisation on the cell. Thus, there is no restriction on low-voltage operation. Furthermore, by employing a compact column-path circuitry which only activates the required 8-bit data, this architecture minimises the current consumption of the memory array. A 2.5-V, 2-Mbit prototype chip has been developed with 0.5-μm CMOS technology, and the possibility of the realisation of GPPG cell architecture has been confirmed.Integrated frequency shifter in periodically poled lithium tantalate waveguide
http://dl-live.theiet.org/content/journals/10.1049/el.2010.2561
A frequency shifting device is fabricated and tested in a ferroelectric waveguide in a low-photorefractivity crystal. Periodic poling for quasi-phase-matching and channels for operation in the near-infrared C-band were obtained in congruent lithium tantalate, demonstrating for the first time both wave confinement and two-stage parametric conversion in such waveguides.Basic operation of novel ferroelectric CMOS circuits
http://dl-live.theiet.org/content/journals/10.1049/el_20083230
A nonvolatile ferroelectric complementary metal-oxide-semiconductor (CMOS) circuit with both logic and memory functions is proposed as a new application of ferroelectric field effect transistors. The logic and memory operations of a NOT-logic ferroelectric CMOS device is demonstrated. Nondestructive readings of high and low output voltage levels of the device were performed. Data retention was measured up to10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">5</sup> s (1.2 days).High-speed and low-power FeRAM utilising merged BL/PL array architecture with twin-bitline-driven scheme
http://dl-live.theiet.org/content/journals/10.1049/el.2009.0173
A novel design method for nonvolatile ferroelectric random access memory (FeRAM) using a merged bitline(BL)/plateline(PL) array architecture with a twin bitline-driven scheme is proposed. This method is effective in improving the FeRAM performance and reduces the power consumption. A 128 Kbit FeRAM prototype applying the proposed circuitry is implemented. The chip size, access time and memory array power dissipation are reduced to about 87, 44 and 15.8%, respectively, in comparison with those of conventional FeRAM.Single-crystal ferroelectric microwave capacitor fabricated by separation by hydrogen implantation
http://dl-live.theiet.org/content/journals/10.1049/el_19990354
Microwave ferroelectric capacitors have been fabricated using separation by hydrogen ion implantation and transfer of a 500 nm thick single-crystal SrTiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> layer to an insulating glass substrate. The capacitor films are of high quality with a measured quality factor of nearly 100 at 10 GHz.Scaling of piezoelectric properties in nanometre to micrometre scale
http://dl-live.theiet.org/content/journals/10.1049/el_20000291
Measurements of piezoelectric response have been performed using atomic force microscopy (AFM) on sol-gel produced lead-zirconate-titanate (PZT) thin films, upon which nanometre- to micrometre-scale electrodes have been patterned. It is found that the magnitude of the piezoelectric response as a function of the electrode size in the range from a few nanometres up to 6 µm can be described accurately in terms of the fringing of the electric field around the electrode edges.Tunability of ferroelectric varactors up to 60 GHz
http://dl-live.theiet.org/content/journals/10.1049/el_20071996
A TRL-multiline de-embedding technique for the determination of the electrical parameters of interdigitated varactors over a broad centimetre–millimetre band is proposed. The method is applied to voltage-controlled ferroelectric (BaSrTiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>) varactors, which exhibit almost constant frequency dependence of the capacitance (ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>∼300) from 10 to 60 GHz. The capacitance ratio is ∼2 for a 30 V bias offset, and the quality factor is of the order 10 at 30 V.Nonvolatile current-sensing device in all-oxide Pb(Zr,Ti)O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub>/BaRuO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> structure
http://dl-live.theiet.org/content/journals/10.1049/el_20045245
A nonvolatile current sensing device using Pb(Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.52</sub>,Ti<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.48</sub>)O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> (PZT) as a gate and BaRuO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> (BRO) as a thin film channel is demonstrated. A nonvolatile change of 33% in the sheet resistance of BRO has been observed as the polarisation of the ferroelectric PZT layer is reversed. This change was nonvolatile after 24 h and the conductivity measurements between 80 and 300 K revealed that the BRO layer shows n-type conduction. The BRO channel is compatible with PZT process and the all-oxide structure offers the possibility of nonvolatile, current-sensing memory devices.RF magnetron sputtered perovskite-oriented PSZT thin films on gold for piezoelectric and ferroelectric transducers
http://dl-live.theiet.org/content/journals/10.1049/el_20063422
Conditions for depositing perovskite-oriented Pb<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.92</sub>Sr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.08</sub>(Zr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.65</sub>Ti<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.35</sub>)O<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> thin films on gold by RF magnetron sputtering are investigated. Deposition results were analysed by scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffractometry. It was found that the desired perovskite phase can be obtained at a substrate temperature of 300°C, much lower than the typically reported 650°C for deposition on platinum.Electrically tunable microwave phase shifter based on layered ferrite-ferroelectric structure
http://dl-live.theiet.org/content/journals/10.1049/el_20010746
A novel electrically tunable microwave phase shifter is proposed based on surface spin wave propagation in a layered structure containing ferrite and ferroelectric materials. Operating characteristics of the phase shifter are investigated theoretically. It is shown that waveguiding elements from planar layered ferrite-ferroelectric structures allow the construction of compact devices with high electrical tunability achieving 10°/V.Miniature antenna based on magnetoelectric composites
http://dl-live.theiet.org/content/journals/10.1049/el_20080325
The design and characterisation of a miniaturised 100 MHz antenna based on magnetoelectric (ME) composites are discussed. Ferrite–ferroelectric composites with high and equal permeability μ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub> and permittivity ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub> have been synthesised and used as the substrate for a microstrip antenna. The composite also facilitates impedance matching to free space. A sample of nickel zinc ferrite and bismuth strontium titanate prepared by ceramic processing and with μ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub>=ɛ<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>r</i></sub> has been used. Scattering parameter data indicates an antenna miniaturisation factor of 7–10 at 100 MHz, in agreement with theory.Effects of fringing capacitor on ferroelectric phase shifter
http://dl-live.theiet.org/content/journals/10.1049/el.2010.3538
Two different devices topology are proposed to implement parallel-plate capacitors using Ba<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.6</sub>Sr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">0.4</sub>TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> (BST) thin films. At 1 MHz frequency, the maximum tunability 1.3:1 is obtained with 32 V DC bias. The new topology capacitors have much higher tunability compared with conventional capacitors at the same total capacitance. Phase shifters, which are loaded variable structure capacitors have also been implemented. The circuits provide a maximum 190° and 262° phase shift at 18 GHz at room temperature.Tunable dielectric resonator with ferroelectric element
http://dl-live.theiet.org/content/journals/10.1049/el_20010731
A method for electrical tuning of a dielectric resonator using a Ba<i xmlns="http://pub2web.metastore.ingenta.com/ns/"><sub>x</sub></i>Sr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">(1-<i>x</i>)</sub>TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> thick film grown on a metal substrate is described. The results show that by incorporating a ferroelectric element, fast resonant frequency tuning of a dielectric resonator, while maintaining a useful <i xmlns="http://pub2web.metastore.ingenta.com/ns/">Q</i>-factor, is possible.FRAM design style utilising bit-plate parallel cell architecture
http://dl-live.theiet.org/content/journals/10.1049/el_20031104
A new FRAM design method utilising the bit-plate parallel cell architecture is presented. This method is effective in reducing circuit and layout overhead caused by on-pitch plate control circuitry. It also reduces the power consumption in memory array. Implementation results for a 0.13 µm, 512 kb FRAM prototype show that the memory block area in the proposed architecture is 15.6% less than that of the conventional structure.High-performance low-cost phase-shifter design based on ferroelectric materials technology
http://dl-live.theiet.org/content/journals/10.1049/el_20046119
A novel approach to ferroelectric phase-shifter design using Ba<sub xmlns="http://pub2web.metastore.ingenta.com/ns/"><i>x</i></sub>Sr<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">1-<i>x</i></sub>TiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">3</sub> (BSTO) films in a multilayer dielectric coplanar waveguide structure is described. By including a low-loss dielectric layer (SiO<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">2</sub>) between the coplanar waveguide conductors and a layer of ferroelectric materials, significant reduction in insertion loss can be achieved in conjunction with a threefold increase in figure of merit (°/dB).Electrically tunable microwave filters based on ferromagnetic resonance in ferrite-ferroelectric bilayers
http://dl-live.theiet.org/content/journals/10.1049/el_20050925
The design and analysis of a new class of electric field-tunable ferrite-ferroelectric microwave bandpass filter is discussed. The tunability is possible through magnetoelectric interactions. When the composite is subjected to an electric field, the mechanical deformation due to piezoelectric effect manifests as a magnetic field shift in the ferromagnetic resonance for the ferrite. The electrical tuning is much faster than traditional magnetic tuning and has practically zero power consumption.Beam scanning of array using ferroelectric phase shifters
http://dl-live.theiet.org/content/journals/10.1049/el_20001155
The beam scanning characteristics of a two-element array utilising a ferroelectric phase shifter are presented for the first time. Applying a DC voltage across the ferroelectric material changes the velocity of the input signal, a beam scan of 26° being achieved. The S<sub xmlns="http://pub2web.metastore.ingenta.com/ns/">11</sub> performance and the radiation patterns of the array at two frequencies are presented.Dual-tunable hybrid wave ferrite-ferroelectric microwave resonator
http://dl-live.theiet.org/content/journals/10.1049/el_20060164
A novel electric and magnetic field tunable microwave resonator with a yttrium iron garnet and barium strontium titanate layered structure is investigated. The measured characteristics at 3.6 GHz, corresponding to the proximity of magnetic and dielectric resonance modes, show a broadband electrical tunability. A tuning range of 1.5% of the central resonance frequency is obtained for nominal electric fields.Operation of single transistor type ferroelectric random access memory
http://dl-live.theiet.org/content/journals/10.1049/el_20046555
Verification was sought for the memory operation of a single transistor type ferroelectric random access memory (1T type FeRAM) with a circuit model for a memory cell transistor combined with a precharged capacitive decoupling sensing scheme. The wiring scheme of the 1T type FeRAM array was also proposed based on the operation of the fabricated memory cell transistor. As a result, the memory operation of 1T type FeRAM was confirmed at a low current level with high sensing speed and no reference cell, and the design and verification of the full chip were achieved.Modelling polarisation of ferroelectric SBT capacitors including temperature dependence
http://dl-live.theiet.org/content/journals/10.1049/el_20010829
A new model for thin film SBT ferroelectric capacitors including temperature behaviour is presented. The model, which is based on the Preisach theory, requires parameters that are physically based and which can be easily extracted from measured data. Iterative procedures are not used in the model, which makes it best suited for use in circuit simulators.Flash [computer memory]
http://dl-live.theiet.org/content/journals/10.1049/ir_20031108
Ever falling chip geometries are beginning to raise serious doubts as to the long-term viability of flash. Quantum tunnelling is integral to the operation of flash memory, and as chips are getting smaller the ultra-thin tunnelling barrier is becoming increasingly prone to breaking down. A second problem is with the lifetime of flash-based devices, which can be limited to around 100000 cycles. This is fine for some applications, but inadequate where data storage requirements extend over decades. Flash is also quite slow and difficult to program, two problems that are getting more significant as chip areas increase and supply voltages fall. There are three technologies looking to replace flash: magnetic RAM (MRAM), ferroelectric RAM (FRAM) and ovonic RAM. All of these use new materials to create truly nonvolatile memories with long lifetimes. Getting any one of them to replace flash in the marketplace will depend on producing a sufficiently small memory cell, while at the same time minimising the number of additional processing steps required.Flat-panel autostereoscopic 3D display
http://dl-live.theiet.org/content/journals/10.1049/iet-opt_20060077
Three-dimensional (3D) autostereoscopic images can be synthesised by scanning the illumination of a sequence of views on a liquid crystal display but few liquid crystal displays have adequate frame rate while simple scanning optics are bulky. A high-framerate ferroelectric microdisplay is combined with a slim front-illuminator comprising a line of light emitting diodes (LEDs) coupled into a slab light-guide embossed with a grating. One view at a time of a 3D object is displayed on the microdisplay while one LED at a time is switched on. The light-guide collimates the emission from the LED across the screen so that each view is made visible to a distinct direction. The result has high resolution and wide field of view, and has the potential to be small and slim enough for use on a mobile phone.Experimental 128-kbit ferroelectric memory with 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sup> endurance and 10-year data retention
http://dl-live.theiet.org/content/journals/10.1049/ip-cds_20020243
An experimental 128-kbit ferroelectric random access memory is presented, which has been designed and fabricated with 0.5 μm ferroelectric storage cell integrated CMOS technology. To achieve stable cell operation, novel design techniques, robust to unstable cell capacitors, are adopted: open bit-line cell array; up–down pulsed plate read/write-back scheme; complementary data preset reference circuitry; and non-ferroelectric reference voltage generator. A self-driven cell plate scheme has also been employed to improve cell array layout efficiency. The prototype chip incorporating these circuit schemes shows 70 ns access time and 120 ns cycle time at 3.3 V and 25°C. The read/write endurance has been confirmed up to 10<sup xmlns="http://pub2web.metastore.ingenta.com/ns/">12</sup> cycles. It has also been observed that memory cells can retain the data for 10 years.