Downscaling ferroelectric field effect transistors by using ferroelectric Si-doped HfO2. Clark — Emerging Applications for High K Materials. Ferroelectric doping can be suggested as a way to overcome these problems. In this method, graphene is doped by the dipole charges modulated by an external voltage applied to ferroelectric material. Thus, local doping is possible in the desired area by using specific methods such as electrostatic force microscopy (EFM). Advances in Non-Volatile Memory and Storage Technology Y. Nishi download Z-Library. Download books for free.

Fefet

Switchable and Tunable Ferroelectric Devices for Adaptive and Reconfigurable RF Circuits

Date of original webcast:Tuesday, January 9, 2018

Duration:1 hour, 1 minute

Summary

The exponential increase in the number of wireless devices as well as the limited wireless spectrum, pose significant challenges in the design of future wireless communication systems. Adaptive and reconfigurable radios that can change their frequency and mode of operation based on the unused/available wireless spectrum have been proposed to address such challenges. Frequency Agile RF circuits play a key role in realization of such radios.

This presentation is on the applications of ferroelectric thin film barium strontium titanate (BST) for the design of frequency agile radios. BST is a low loss, high dielectric constant field dependent multifunctional material. The electric field dependence of BST has been employed to design tunable RF and microwave devices and components. Another important property of BST is its DC electric field induced piezoelectric or electrostrictive effect. These properties are utilized to design intrinsically switchable film bulk acoustic wave resonators (FBARs) and FBAR filters. Switchable ferroelectric based filter banks can significantly reduce size and power consumption of conventional filter banks employed in frequency agile radios. Design of several BST based adaptive and reconfigurable RF circuits will be presented.

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Speakers

Amir Mortazawi

Professor of Electrical Engineering
University of Michigan

Amir Mortazawi received the Ph.D. degree in electrical engineering from The University of Texas at Austin, in 1990. He is currently a Professor of electrical engineering with The University of Michigan at Ann Arbor. His research interests include microwave and millimeter-wave circuits, phased arrays, power amplifiers, ferroelectric thin film based devices and frequency-agile microwave circuits.

Mortazawi was the Editor-in-Chief for the IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES from 2006-2010. He served on the IEEE Microwave Theory and Techniques Society (IEEE MTT-S) Administrative Committee (AdCom) for eight years. Mortazawi served as the Associate Editor for the IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION (1998–2001) and IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES (2005). Mortazawi is a Fellow of IEEE.

Michael C. Hamilton

Dr. Michael C. Hamilton is an Associate Professor in the Electrical and Computer Engineering Department at Auburn University and the Assistant Director of the Alabama Microelectronics Science and Technology Center.

Книги по разным темамPages: | 1 | 2 | Физика твердого тела, 2001, том 43, вып. 7 General Features of the Intrinsic Ferroelectric Coercive Field й V.M. Fridkin, Stephen Ducharme Department of Physics and Astronomy, Center for Material Research and Analysis University of Nebraska, 68588-0111 Lincoln, USA Shubnikov Institute of Crystallography, Russian Academy of Sciences, 117333 Moscow, Russia E-mail: sducharme1@unl.edu fridkin@ns.crys.ras.ru (Поступила в Редакцию 14 декабря 2000 г.) The value of the intrinsic ferroelectric coercive field is obtained independently from general energy considerations and from the predictions of several models of the ferroelectric state. All predictions yield a value of order of the depolarization field, which is equal to the spontaneous polarization divided by the dielectric permittivity, and are consistent with the recent measurements of the intrinsic ferroelectric coercive field in ultrathin Langmuir-Blodgett films of copolymers of polyvinylidene fluoride with trifluoroethylene. Prior studies had succeeded only in measuring the much smaller extrinsic coercive fields, which are limited by nucleation processes and domain motion.

This work was supported by the USA National Science Foundation and the Nebraska Research Initiative.

Ferroelectric Fets Diagram

The defining characteristic of a ferroelectric is the abi- sequently there has been relatively little published discussion lity repeatably to reverse, or switch, the polarization by of intrinsic switching, except to note that it remained out application of a sufficiently large external electric field as of reach. The thin ferroelectric films have indeed shown illustrated by the hysteresis loops in Fig. 1. Yet since the the nucleation-inhibition finite site effect, an increase of the discovery of ferroelectricity eighty years ago by Valasek, coercive field with the decrease of thickness, but the value few published reports have considered the value of the of the measured coercive field was still much lower than intrinsic coercive field connected with collective polarization the intrinsic one and correspondingly the switching is still reversal, a consequence of the instability of the macroscopic controlled by the nucleation and domains. Recently [12], we polarization state in an opposing electric field. This is succeeded in finding the limiting intrinsic coercive field in because the measured value of the ferroelectric coercive field films as thin as 1 nm made by LangmuirЦBlodgett(LB) dehas been invariably much smaller than the intrinsic value position of a two-dimensional ferroelectric copolymer [13].

predicted by theory, such as the LandauЦGinzburg (LG) mean field model [1] or by ferroelectric Ising model [2,3].

The low extrinsic coercive field observed in real ferroelectric crystals and films is caused by nucleation of domains with reversed polarization, which then grow and coalesce by domain wall motion [2,4,5]. Nucleation can occur at fixed defects in the crystal or due to a passive (nonferroelectric) surface layer [6]. Nucleation mechanisms and domain wall dynamics must be arbitrarily inserted into these models in order to explain the experimental observations of switching kinetics with much lower coercive fields in real ferroelectric materials [2]. In fact, the study and modeling of extrinsic switching is a great industry in the field and is central to the application of ferroelectric films to nonvolatile randomaccess memories [7].

It has proven difficult to prevent extrinsic switching by eliminating defects or pinning domain walls. Another way to achieve intrinsic switching is to make a particle small enough or a film thin enough to inhibit nucleation [5,8Ц10]. Several mechanisms for this finite-size effect have been proposed, including reduction of nucleation volume, introduction of space charge near the electrodes, elimination of passive layers, and domain-wall pinning [4,6,10,11]. Even in the Figure 1. Theoretical ferroelectric hysteresis loops from the firstthinnest ferroelectric films obtained previously, the measured order LandauЦGinzburg model (solid line), second-order Landau - Ginzburg model (dashed line), Ising-Devonshire model (dotted extrinsic coercive field is much smaller than the expected line).

intrinsic value calculated from theoretical models, and conGeneral Features of the Intrinsic Ferroelectric Coercive Field The measured values of the intrinsic coercive field were cive field can be written as in good agreement with the predictions of the LG mean- 3 3 PS field theory [1,14]. Here, we analyze the calculation of the Ec 1 - t (from LG1). (2) 0 25 intrinsic coercive field from a more general perspective and from several specific models of ferroelectricity.

The value of the intrinsic coercive field Ec near the Curie We can estimate the intrinsis ferroelectric coercive field Ec temperature T0 is about 1/10 of the depolarization field.

by calculating the external electric field necessary to over- The LandauЦGinzburg continuous ferroelectric