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Topic: Ferroelectric

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	United States Patent: 6,420,742 (Site not responding. Last check: 2007-10-08)
		Currently, there are two types of conventional ferroelectric memory devices: one which uses a transistor to detect the amount of charge stored in a capacitor, and one which detects a change in the resistance of a transistor caused by the spontaneous polarization of a ferroelectric material.
		An example of the second type of ferroelectric memory device is a ferroelectric insulator semiconductor field-effect transistor (FET), which employs a ferroelectric film instead of the conventional gate insulating film, and in which the read-out operation is performed by forming an inversion layer in a channel region of the transistor.
		Similarly, the term "ferroelectric material" is intended to include not only elemental ferroelectric material, but ferroelectric material with other trace elements or trace metals, or in various alloyed combinations with other ferroelectric materials known in the semiconductor industry, as long as the physical and electrical properties of the ferroelectric material remain unchanged.
	web.engr.oregonstate.edu /~flf/6420742.html (6710 words)

	Ferroelectric effect - Wikipedia, the free encyclopedia
		Another important ferroelectric material is lead zirconate titanate.
		By analogy to magnetic core memory, this hysteresis can be used to store information in ferroelectric RAM, which has ferroelectric capacitors as memory cells.
		The nature of the phase transition in some ferroelectric crystals is still not well understood.
	en.wikipedia.org /wiki/Ferroelectric_effect (280 words)

	Are Films Ferroelectric? (Site not responding. Last check: 2007-10-08)
		Ferroelectric materials known as perovskites, of which lead titanate is one, share their crystal structure with the mineral perovskite, and are being keenly investigated by researchers for new applications in microelectronics.
		Ferroelectric materials are already being used in microelectronic devices, such as non-volatile random access memory (NVRAM), that exploit ferroelectricity to store information.
		If this problem proved to be the result of a fundamental incompatibility between ferroelectricity and reduced thickness, it might present a lower limit on the size of microelectronic components based on such materials.
	www.aps.anl.gov /Science/Highlights/2004/bessrc_science.htm (710 words)

	World Intellectual Property Organization (Site not responding. Last check: 2007-10-08)
		Ferroelectrics are electrically polarizable materials that possess at least two equilibrium orientations of the spontaneous polarization vector in the absence of an external electrical field, and in which the spontaneous polarization vector may be switched between those orientations by an electric field.
		A layer of ferroelectric material is provided between the electrode sets in a capacitor-like structure such that memory cells are defined in the ferroelectric material between the electrode crossings.
		As the method according to the present invention concerns ferroelectric memory devices and particularly wherein the ferroelectric memory material is a polymer, an example of a ferroelectric memory device of this kind shall be given in order to ease the understanding of its function.
	www.wipo.int /ipdl/IPDL-CIMAGES/view/pct/getbykey5?KEY=03/107351.031224&ELEMENT_SET=DECL (4717 words)

	United States Patent Application: 0030027360
		A ferroelectric transistor structure comprising: a) a ferroelectric gate overlying a semiconductor substrate; b) and a high-k material interposed between the ferroelectric gate and the semiconductor substrate.
		A ferroelectric transistor structure comprising a ferroelectric gate having a bottom, sides and a top, overlying a semiconductor substrate, wherein the ferroelectric gate is encapsulated by the combination of a high-k material on the bottom and the sides and a top electrode on the top.
		Plasma etching degrades the ferroelectric properties of the ferroelectric gate, thereby reducing the reliability of the memory transistor.
	appft1.uspto.gov /netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PG01&p=1&u=/netahtml/PTO/srchnum.html&r=1&f=G&l=1&s1='20030027360'.PGNR.&OS=DN/20030027360&RS=DN/20030027360 (3297 words)

	NPL: Definitions
		Aging of ferroelectrics is a logarithmic function with time, with the most important parameters that age with time being dielectric constant, resonant frequency and the frequency constants.
		This is defined as the temperature at which a ferroelectric material undergoes a crystallographic phase change from an asymmetrical, non-centrosymmetric structure to a centrosymmetric crystal structure, thus losing it spontaneous polarisation.
		ferroelectric phases originate form a non-polar prototypic phase and all of the polarisation is reorientable.
	www.npl.co.uk /materials/functional/definitions.html (1443 words)

	Ferroelectric effect -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-08)
		In (The science of matter and energy and their interactions) physics, the ferroelectric effect is an (A physical phenomenon involving electricity) electrical phenomenon whereby certain ionic (A crystalline element used as a component in various electronic devices) crystals may exhibit a spontaneous (The moment of a dipole) dipole moment.
		Ferroelectric crystals often show several (The temperature above which a ferromagnetic substance loses its ferromagnetism) Curie points and domain structure hysteresis, much as do ferromagnetic crystals.
		Ferroelectrics often have very large (Click link for more info and facts about dielectric constant) dielectric constants, and thus are often found in (An electrical device characterized by its capacity to store an electric charge) capacitors.
	www.absoluteastronomy.com /encyclopedia/f/fe/ferroelectric_effect.htm (362 words)

	Ferroelectric liquid crystals from achiral molecules
		This forms the basis for conventional ferroelectric liquid crystals, in which the bulk polarization lies within the plane of the smectic layers.
		Ferroelectricity is demonstrated by measurements of an acoustically induced piezoelectric response and the determination of repolarization currents.
		The mechanism by which the polar phase is generated differs from that found in conventional chiral smectics, and should in principle allow the preparation of a phase in which the bulk polarization is parallel to the long axis of the constituent molecules.
	www.nature.com /cgi-taf/DynaPage.taf?file=/nature/journal/v359/n6396/abs/359621a0.html (253 words)

	Process for manufacturing a ferroelectric device and devices manufactured thereby - Patent 4195355
		It is a further object of the present invention to provide processes for manufacturing ferroelectric devices, and devices manufactured thereby, which prevent the reversion of phase III potassium nitrate to phase II potassium nitrate.
		In particular, ferroelectric devices made in accordance with the process of the present invention have been switched at a rep rate of 833,333 hertz for 12,026 seconds.
		It should also be borne in mind that, unlike nitride memories, retention time for the ferroelectric devices produced in accordance with the present invention is not a function of write time.
	www.freepatentsonline.com /4195355.html (2250 words)

	New Details of Ferroelectric Switching (Site not responding. Last check: 2007-10-08)
		Ferroelectric materials are of special interest to developers of the next generation of such devices because they exhibit polarized electronic states that can represent bits of information.
		Moreover, these materials retain their polarization states without consuming electrical power, making ferroelectrics the subject of intense study for nonvolatile memory applications in which data is stored even when the power is turned off.
		Images of the stored polarization with the ferroelectric layer were obtained by scanning the x-ray beam across the device.
	www.aps.anl.gov /Science/Highlights/2004/ferroelectric_switching.htm (933 words)

	United States Patent: 6,586,792 (Site not responding. Last check: 2007-10-08)
		One problem that hinders the continued down-scaling of conventional ferroelectric memory transistors is the vulnerability of their gate insulations to failure at thinner dimensions.
		The exemplary embodiment sets the thickness of the weak ferroelectric layer at 630 nanometers, which is measured in a dimension parallel to the applied electric fields.
		Some embodiments restrict the ferroelectric thickness to be greater than the thickness of insulator layer 310, while others use a ferroelectric layer thickness that facilitates programming of the ferroelectric layer, that is, change of its polarization state, at an applied voltage less than the breakdown voltage of gate insulation layer 14.
	web.engr.oregonstate.edu /~flf/6586792.html (4048 words)

	United States Patent: 5,900,390 (Site not responding. Last check: 2007-10-08)
		Candidate ferroelectrics include a mixture of strontium titanate and lead titanate, a mixture of strontium and barium titanate, KTa.sub.1-x Nb.sub.x O.sub.3 where the value of x is between 0.005 and 0.7, a composition of powdered mixture of strontium titanate and lead titanate and polythene powder, potassium dihydrogen phosphate, triglycine sulphate.
		The variables in the coaxial filter construction are (1) the diameter of the outer conductor, (2) the diameter of the inner conductor, (3) the type of ferroelectric material, (4) the type of conductor material used for the outer conductor and (5) the type of conductor material used for the inner conductors.
		Different ferroelectrics, ferroelectric liquid crystals (FLC), dielectrics, impedances, high Tc superconductors, number of cavities, diameters of inner and outer coaxial conductors, sizes of irises, types of irises, dielectric filled and air filled coaxial transmission lines are contemplated.
	spore.patentmatrix.com /Projects/WNCCTC/BOS/5900390.html (4796 words)

	Ferroelectric Materials (Site not responding. Last check: 2007-10-08)
		Ferroelectric single crystals grown in the absence of an electric field are inevitably electrically twinned, with a domain volume containing a given spontaneous polarization direction approximately equal to that containing the antiparallel direction.
		Switched ferroelectrics are employed in matrix addressed memories, shift registers and switches known as transchargers or transpolarizers.
		The linear or quadratic electrooptic effect in ferroelectrics is employed in light deflectors, modulators and displays, and the nonlinear optical effect in second harmonic generation, frequency mixing and optical parametric oscillation.
	www.sou.edu /physics/ferro/nsf_wht.htm (1839 words)

	Thin-Film Ferroelectric Tunable Microwave Devices
		Thin ferroelectric films are one of the major technologies competing to fill these applications.
		When a direct-current (dc) voltage is applied to ferroelectric film, the dielectric constant of the film can be decreased by nearly an order of magnitude, changing the high-frequency wavelength in the microwave device.
		Direct-current bias is applied between the coupled microstrips, strongly affecting the dielectric constant of the ferroelectric in the gap and causing a microwave phase shift.
	www.lerc.nasa.gov /WWW/RT1998/5000/5620vankeuls.html (819 words)

	MPI-MSP Halle, nanoscale ferroelectric oxides
		On the other hand the questions to know whether ferroelectric structures that have submicron size (lateral and in height) are still ferroelectric, are still switching, and whether they still possess an equilibrium domain pattern are fundamental questions to be addressed before scaling down ferroelectric devices.
		Topography image of an array of ferroelectric PZT cells prepared by imprint lithography (left) and piezoresponse image of the same array (at the same magnification) after switching serveral cells using d.c.
		It allows the characterization of ferroelectric thin films at a nanoscopic scale, as well as the investigation of their ferroelectric behavior in dependence on their micro- or nano-structure.
	www.mpi-halle.mpg.de /~functio/nfo.html (392 words)

	Electron beam generation using ferroelectric plasma cathodes (Site not responding. Last check: 2007-10-08)
		Several different ferroelectric samples were studied under the application of driving pulses with either a positive or negative polarity.
		The operation of planar and coaxial electron diodes with the tested ferroelectric cathodes were studied under the application of a high-voltage pulse having an amplitude of 25 - 250 kV.
		It was found that the electron beam parameters as well as the electron diode parameters depend strongly on the method of the plasma formation and the time delay between the high-voltage pulse application and the beginning of the plasma formation.
	flux.aps.org /meetings/YR99/DPP99/abs/S460003.html (214 words)

	Ferroelectric Materials and Microwave Applications
		Ferroelectric materials such as PZT have been refined for use in static memories, and may be useful in microwave control applications.
		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.
		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.
	www.mtt.org /symposia/ims/2000/wfe.htm (1749 words)

	Three-terminal non-volatile ferroelectric/superconductor thin film field effect transistor (Site not responding. Last check: 2007-10-08)
		A ferroelectric thin film is then epitaxially grown on the superconducting layer to form the gate of the FSuFET.
		In static mode, the two polarization states of the ferroelectric gate correspond to the binary "0" and "1" states, which are switched by applying a voltage pulse of sufficient magnitude.
		In transient mode, the four states depend upon the polarization state of the ferroelectric gate and the conductive state (superconducting or non-superconducting) of the drain-source channel.
	www.svec.uh.edu /pat-5686745-abs.html (197 words)

	Ferroelectric Thin-Film-Based Frequency and Phase Agile Microwave Components for Communication Applications (Site not responding. Last check: 2007-10-08)
		These structures capitalize on the nonlinear response of the dielectric constant of the ferroelectric films when biased with a dc electric field.
		Emphasis is placed on the deposition parameters required for optimal ferroelectric thin-film growth (i.e., maximum tunability and lowest loss) and the study of different circuit designs for determining which configurations are most advantageous in terms of tunability, losses, and required bias for a given communication application.
		We are optimizing thin-film ferroelectric/dielectric structures to develop tunable phase shifters for phased array antennas, low phase noise tunable local oscillators, and tunable pre-select filters for receiver front-end at frequencies from X-Band to V-band.
	www4.nationalacademies.org /pga/rap.nsf/ByTitle/44.54.88.B4831?OpenDocument (351 words)

	FERROELECTRIC MATERIALS (Site not responding. Last check: 2007-10-08)
		In the Laboratory of Ferroelectric Materials,Department of Materials Physics, C-IV (UAM), research in ferroelectrics is being carried out for the last twenty years.
		Many applications of ferroelectric materials come from their pyroelectric (infrared detectors, energy converters), and piezoelectric (transducers) properties; but the more relevant are those based on its own characteristic behavior, the possibility to reverse its spontaneous polarization under the influence of an external field (switching).
		In order to observe the hysteresis loops of the ferroelectric materials, a classical DDP bridge, connected to an oscilloscope, is being used.
	www.uam.es /otroscentros/inc/grupos/memoria/jgonzalo.html (667 words)

	Stephen Ducharme
		Ferroelectrics, which have built-in electric fields, are similar to ferromagnets, which have built-in magnetic fields.
		The discovery of two-dimensional ferroelectricity was was cited as one of 30 "especially important and interesting problems" in physics and astrophysics on the verge of the 21st century, in the April 1999 issue of Physics Uspekhi (the leading Russian physics review journal) by editor-in-chief, V. Ginzburg.
		The ferroelectric polymer capacitors could replace batteries in a wide range of devices, ranging from electric vehicles to cell phones to laptops, and could also replace some of the trillions of discrete capacitors installed every year in electronic devices.
	www.physics.unl.edu /directory/ducharme/ducharme.html (1887 words)

	Thermodynamics of Epitaxial Ferroelectric Thin Films (Site not responding. Last check: 2007-10-08)
		The goal of this study is to develop the thermodynamic description of epitaxial ferroelectric thin films on thick substrates.
		Results: A phenomenological thermodynamic theory of ferroelectric thin films epitaxially grown on cubic substrates is developed using a new form of the Gibbs function, which corresponds to the actual mechanical boundary conditions of the problem.
		According to the diagram three ferroelectric phases can be stable in films of this materials: c-phase where one out-of-plane component of the polarisation differs from zero, aa-phase where two in-plane equal components of the polarisation differ from zero, and r-phase where three components of the polarisation differ from zero.
	dmxwww.epfl.ch /lc/Research96-7/b108.html (338 words)

	Ferroelectric Memory Research Group at the University of Toronto (Site not responding. Last check: 2007-10-08)
		Ferroelectric Memory Research Group (FMRG) at the University of Toronto:
		This page is designed to provide you with the most recent information on Ferroelectric Memory Research Group (FMRG) in the Department of Electrical and Computer Engineering at the University of Toronto.
		We have proposed a ferroelectric capacitor macromodel for FeRAM circuit simulations.
	www.eecg.toronto.edu /~ali/ferro.html (364 words)

	Research Programs
		This project focuses on the engineering of artificially layered ferroelectric superlattices and compositionally graded ferroelectric films with enhanced properties through spatial variations in internal stresses, film composition, and microstructure.
		Making use of the unique intrinsic characteristics of ferroelectric materials and introducing compositional and internal stress gradients, exceptional and unusual electrical and electromechanical properties can be obtained which are not possible for bulk ferroelectrics and ferroelectric thin films.The ongoing work is a combined experimental and theoretical effort.
		Formation of polydomain (polytwin) structures in epitaxial films undergoing a phase transformation is a mechanism that relaxes internal stresses that are a result of the lattice misfit due to the structural phase transformation and the difference in the thermal expansion coefficients of the film and the substrate.
	www.ims.uconn.edu /~alpay/P_Web/research.htm (400 words)

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