This review covers important advances in recent years in the physics of thin-film ferroelectric oxides, the strongest emphasis being on those aspects particular to ferroelectrics in thin-film form. The authors introduce the current state of development in the application of ferroelectric thin films for electronic devices and discuss the physics relevant for the performance and failure of these devices. Following this the review covers the enormous progress that has been made in the first-principles computational approach to understanding ferroelectrics. The authors then discuss in detail the important role that strain plays in determining the properties of epitaxial thin ferroelectric films. Finally, this review ends with a look at the emerging possibilities for nanoscale ferroelectrics, with particular emphasis on ferroelectrics in nonconventional nanoscale geometries.

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Physics of thin-film ferroelectric oxides

An overview of the state of art in ferroelectric thin films is presented. First, we review applications: microsystems' applications, applications in high frequency electronics, and memories based on ferroelectric materials. The second section deals with materials, structure (domains, in particular), and size effects. Properties of thin films that are important for applications are then addressed: polarization reversal and properties related to the reliability of ferroelectric memories, piezoelectric nonlinearity of ferroelectric films which is relevant to microsystems' applications, and permittivity and loss in ferroelectric films-important in all applications and essential in high frequency devices. In the context of properties we also discuss nanoscale probing of ferroelectrics. Finally, we comment on two important emerging topics: multiferroic materials and ferroelectric one-dimensional nanostructures. (c) 2006 American Institute of Physics.

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Ferroelectric thin films: Review of materials, properties, and applications

This paper reviews deposition, integration, and device fabrication of ferroelectric PbZrxTi1-xO3 (PZT) films for applications in microelectromechanical systems. As examples, a piezoelectric ultrasonic micromotor and pyroelectric infrared detector array are presented. A summary of the published data on the piezoelectric properties of PZT thin films is given. The figures of merit for various applications are discussed. Some considerations and results on operation, reliability, and depolarization of PZT thin films are presented.

http://iopscience.iop.org/article/10.1088/0960-1317/10/2/307/pdf

Ferroelectric thin films for micro-sensors and actuators: a review

Novel memory cells utilize source-side injection, allowing very small programming currents. If desired, to-be-programmed cells are programmed simultaneously while not requiring an unacceptably large programming current for any given programming operation. In one embodiment, memory arrays are organized in sectors with each sector being formed of a single column or a group of columns having their control gates connected in common. In one embodiment, a high speed shift register is used in place of a row decoder to serially shift in data for the word lines, with all data for each word line of a sector being contained in the shift register on completion of its serial loading. In one embodiment, speed is improved by utilizing a parallel loaded buffer register which receives parallel data from the high speed shift register and holds that data during the write operation, allowing the shift register to receive serial loaded data during the write operation for use in a subsequent write operation. In one embodiment, a verification is performed in parallel on all to-be-programmed cells in a column and the bit line current monitored. If all of the to-be-programmed cells have been properly programmed, the bit line current will be substantially zero. If bit line current is detected, another write operation is performed on all cells of the sector, and another verify operation is performed. This write/verify procedure is repeated until verification is successful, as detected or substantially zero, bit line current.

Eeprom with split gate source side injection

This paper provides a detailed overview of developments in transducer materials technology relating to their current and future applications in micro-scale devices. Recent advances in piezoelectric, magnetostrictive and shape-memory alloy systems are discussed and emerging transducer materials such as magnetic nanoparticles, expandable micro-spheres and conductive polymers are introduced. Materials properties, transducer mechanisms and end applications are described and the potential for integration of the materials with ancillary systems components is viewed as an essential consideration. The review concludes with a short discussion of structural polymers that are extending the range of micro-fabrication techniques available to designers and production engineers beyond the limitations of silicon fabrication technology.

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New materials for micro-scale sensors and actuators An engineering review

Stoichiometric films of bismuth titanate, Bi4Ti3O12, have been grown for the first time by the technique of pulsed excimer laser deposition. Ferroelectric films were obtained at temperatures as low as 500 °C on Si(100), MgO(110), and Pt‐coated Si(100) substrates. Hysteresis measurements using a Pt‐coated Si sample yielded a saturation polarization value of about 28 μC/cm2, consistent with a randomly oriented titanate film structure. A preliminary metal‐insulator‐semiconductor sandwich structure of the form Bi4Ti3O12‐CaF2(100 A)‐Si was grown and used to examine polarization induced memory switching effects.

Pulsed laser deposition and ferroelectric characterization of bismuth titanate films

Recent advances in the development of high quality thin films of ferroelectric materials have created renewed interest in ferroelectric random access memory (FERRAM) devices. At the present time, several groups are pursuing the development of FERRAMs, where a thin film ferroelectric capacitor memory element is integrated either adjacent to or directly above the circuit elements in a standard silicon or gallium arsenide integrated circuit. However, these designs provide destructive readout (DRO) only. An alternative monolithic device concept, where the ferroelectric thin film is integrated directly into the semiconductor field effect transistor (FET) element, provides not only nonvolatility, but also nondestructive readout (NDRO). For DRO FERRAM structures, lead–zirconate–titanate is the most widely investigated material at present. At Westinghouse, we are concentrating our efforts on the NDRO ferroelectric memory FET approach, using barium magnesium fluoride (BaMgF4) and bismuth titanate (Bi4Ti3O12) thin films. In this paper, we shall review the current status of the integration of ferroelectric thin films into nonvolatile memory devices, with special emphasis on our own results using BaMgF4 and Bi4Ti3O12.

Integration of ferroelectric thin films into nonvolatile memories

A ferroelectric device that comprises a polarizing thin film of BaMF4 deposited on a substrate. Ba is barium, M is one of the metals of the group consisting of iron (FE), manganese (Mn), cobolt (Co), nickel (Ni), magnesium (Mg), and zinc (Zn). The substrate is silicon, sapphire, or gallium arsenide. A non-volatile NDRO and DRO memory cell and methods for depositing the thin film. A method of depositing bismuth titanate on a substrate are described.

Ferroelectric thin film material, method of deposition, and devices using same

A CCD focal plane processor having a plurality of columns of individual sensor elements with plural sensor elements per column. The structure includes plural CCD shift registers corresponding to the number of columns of sensors, each CCD shift register including a pair of stages corresponding to each of the element sensors of the corresponding column of the array. Two "snapshots" of the scene are taken at time-displaced intervals and are compared to detect differences therebetween to eliminate background, or unchanging scene content. The individual sensors provide outputs which are injected into the α stages of the corresponding paired shift register stages of each CCD shift register in a first time interval corresponding to the first "snapshot". The resulting charge packets in the first (α) stages then are advanced to the second (β) stages of each shift register pair. The second "snapshot" corresponds to injecting a second signal into the α stages of the plurality of pairs of α, β stages. The CCD shift registers then are read out simultaneously and in succession as to the plural, related α, β pairs of stages containing the time-displaced elemental signal samples. A further CCD shift register including a number of α, β pairs of stages receives the parallel α, β outputs in corresponding time sequential manner to maintain the α, β related pair arrangement of the time-displaced elemental samples. An output circuit compares the α, β signals for each elemental area and determines the difference therebetween. A CRT display receives the difference signal outputs for displaying moving target information.

CCD focal plane processor for moving target imaging

Experimental data are presented that confirm ferroelectric thin films of BaMgF4 can be grown by ultrahigh vacuum (UHV) sublimation on semiconductor and metallized substrates at temperatures below 500 °C. Hysteresis properties of the films are shown to be qualitatively consistent with those measured on thinned single‐crystal samples cut perpendicular to the ferroelectric (orthorhombic) a axis. Loops from weakly oriented films on Si(100) display a Pr/Ps ratio of approximately 0.84, with Ps =1.6 μC/cm2 and EC =150 kV/cm. These values are explained on the basis of the film orientation and the measured properties for the bulk crystals. Metal–insulator–semiconductor structures formed with fluoride layers grown on lightly doped Si substrates yielded C–V switching properties indicating their suitability for use in high‐performance ferroelectric field‐effect transistor memory structures. In particular, switching attributable to polarization charge reversal inside the ferroelectric layer, rather than by tunnel inje...

Donald R. Lampe

Papers

Pulsed laser deposition and ferroelectric characterization of bismuth titanate films

Integration of ferroelectric thin films into nonvolatile memories

Ferroelectric thin film material, method of deposition, and devices using same

CCD focal plane processor for moving target imaging

Growth and characterization of ferroelectric BaMgF4 films