The Experts below are selected from a list of 20661 Experts worldwide ranked by ideXlab platform

S Tehrani - One of the best experts on this subject based on the ideXlab platform.

  • low power switching in magnetoresistive random access memory bits using enhanced permeability dielectric films
    Applied Physics Letters, 2007
    Co-Authors: Srinivas V Pietambaram, J.m. Slaughter, Nicholas D Rizzo, R W Dave, J Goggin, K Smith, S Tehrani
    Abstract:

    We reduced the switching field (Hsw) in arrays of single-layer magnetoresistive random access memory elements using enhanced permeability dielectric (EPD) films. This reduction is due to an increased magnetic flux density produced at the bit by increasing the permeability μ of the surrounding dielectric. The authors produced EPD films by embedding superparamagnetic nanoparticles of various sizes in oxides of Al, Mg, or Si. For bits surrounded by EPD, Hsw decreased linearly as μ increased. Using this approach, we reduced Hsw by ≈40% for μ=3.5, without changing the energy barrier to magnetization reversal.

  • magnetoresistive random access memory using magnetic tunnel junctions
    Proceedings of the IEEE, 2003
    Co-Authors: S Tehrani, M. Durlam, M. Deherrera, J.m. Slaughter, B.n. Engel, Nicholas D Rizzo, J Janesky, J Salter, R W Dave, Brian R Butcher
    Abstract:

    Magnetoresistive random access memory (MRAM) technology combines a spintronic device with standard silicon-based microelectronics to obtain a combination of attributes not found in any other memory technology. Key attributes of MRAM technology are nonvolatility and unlimited read and write endurance. Magnetic tunnel junction (MTJ) devices have several advantages over other magnetoresistive devices for use in MRAM cells, such as a large signal for the read operation and a resistance that can be tailored to the circuit. Due to these attributes, MTJ MRAM can operate at high speed and is expected to have competitive densities when commercialized. In this paper, we review our recent progress in the development of MTJ-MRAM technology. We describe how the memory operates, including significant aspects of reading, writing, and integration of the magnetic material with CMOS, which enabled our recent demonstration of a 1-Mbit memory chip. Important memory attributes are compared between MRAM and other memory technologies.

  • thermally activated magnetization reversal in submicron magnetic tunnel junctions for magnetoresistive random access memory
    Applied Physics Letters, 2002
    Co-Authors: Nicholas D Rizzo, M. Deherrera, J.m. Slaughter, B.n. Engel, J Janesky, S Tehrani
    Abstract:

    We have measured thermally activated magnetization reversal of the free layers in submicron magnetic tunnel junctions to be used for magnetoresistive random access memory. We applied magnetic field pulses to the bits with a pulse duration tp ranging from nanoseconds to 0.1 ms. We have measured the switching probability as a function of tp with a fixed field amplitude H, and as a function of H for fixed tp. For both cases, we find good agreement with the switching probability predicted by the Arrhenius–Neel theory for thermal activation over a single energy barrier.

  • submicron spin valve magnetoresistive random access memory cell
    Journal of Applied Physics, 1997
    Co-Authors: Eugene Youjun Chen, M. Durlam, S Tehrani, Theodore Zhu, Herbert Goronkin
    Abstract:

    Spin valve magnetoresistive random access memory cells with widths varying from 1.5 to 0.25 μm and an aspect ratio of length/width more than 10 were fabricated and tested. In general, the switching field of the free magnetic layer was found to be inversely proportional to the width of the cell. Adequate pinning was shown for cell width down to 0.75 μm. For 0.5 and 0.25 μm wide cells, the switching field of the free magnetic layer is comparable to the pinning field of the other magnetic layer. So the pinned magnetic layer rotates with the free magnetic layer. The giant magnetoresistive ratio of the cell drops dramatically. Potentially, this may be a fundamental problem for this memory mode. Solutions are proposed.

Kinam Kim - One of the best experts on this subject based on the ideXlab platform.

  • phase change behavior of stoichiometric ge2sb2te5 in phase change random access memory
    Journal of The Electrochemical Society, 2007
    Co-Authors: Jongbong Park, Gyeongsu Park, Hionsuck Baik, Jangho Lee, Hongsik Jeong, Kinam Kim
    Abstract:

    We observed the atomic structures for each reset and set state in a phase-change random access memory fabricated using stoichiometric crystalline Ge 2 Sb 2 Te 5 . The reset state clearly showed a mixture of dome-shaped amorphous and crystal structure surrounding amorphous, but the set state showed abnormally grown large grains due to recrystallization of the amorphous structure. The crystal structure of the recrystallized grain was face-centered cubic. The element analysis indicated that the atomic composition changes to nonstoichiometric phase in the active regions of the reset and the set state, which is Sb-rich and Te-deficient compared to the pristine stoichiometric composition. Analysis showed that thermal interdiffusion of Sb and Te caused nonstoichiometric nature of the material to reach the energetically stable state in the active region.

  • Integration of lead zirconium titanate thin films for high density ferroelectric random access memory
    Journal of Applied Physics, 2006
    Co-Authors: Kinam Kim, Sung-yung Lee
    Abstract:

    Interests are being focused on types of nonvolatile memories such as ferroelectric random access memory (FRAM), phase change random access memory, or magnetoresistance random access memory due to their distinct memory properties such as excellent write performance which conventional nonvolatile memories do not possess. Among these types of nonvolatile memories, FRAM whose cell structure and operation are almost identical to dynamic random access memory (DRAM) can ideally realize cell size and speed of DRAM. Thus FRAM is the most appropriate candidate for future universal memory where all memory functions are performed with a single chip solution. Due to the poor ferroelectric properties of downscaled ultrathin lead zirconium titanate (PZT) capacitors as well as technical issues such as hydrogen and plasma related degradation arising from embedding ferroelectric metal-insulator-metal capacitors into conventional complementary metal oxide semiconductor processes, current FRAM still falls far below its ideal...

Joerg Appenzeller - One of the best experts on this subject based on the ideXlab platform.

  • fetram an organic ferroelectric material based novel random access memory cell
    Nano Letters, 2011
    Co-Authors: Joerg Appenzeller
    Abstract:

    Science and technology in the electronics area have always been driven by the development of materials with unique properties and their integration into novel device concepts with the ultimate goal to enable new functionalities in innovative circuit architectures. In particular, a shift in paradigm requires a synergistic approach that combines materials, devices and circuit aspects simultaneously. Here we report the experimental implementation of a novel nonvolatile memory cell that combines silicon nanowires with an organic ferroelectric polymer—PVDF-TrFE—into a new ferroelectric transistor architecture. Our new cell, the ferroelectric transistor random access memory (FeTRAM) exhibits similarities with state-of-the-art ferroelectric random access memories (FeRAMs) in that it utilizes a ferroelectric material to store information in a nonvolatile (NV) fashion but with the added advantage of allowing for nondestructive readout. This nondestructive readout is a result of information being stored in our cell...

  • fetram an organic ferroelectric material based novel random access memory cell
    Nano Letters, 2011
    Co-Authors: Joerg Appenzeller
    Abstract:

    Science and technology in the electronics area have always been driven by the development of materials with unique properties and their integration into novel device concepts with the ultimate goal to enable new functionalities in innovative circuit architectures. In particular, a shift in paradigm requires a synergistic approach that combines materials, devices and circuit aspects simultaneously. Here we report the experimental implementation of a novel nonvolatile memory cell that combines silicon nanowires with an organic ferroelectric polymer—PVDF-TrFE—into a new ferroelectric transistor architecture. Our new cell, the ferroelectric transistor random access memory (FeTRAM) exhibits similarities with state-of-the-art ferroelectric random access memories (FeRAMs) in that it utilizes a ferroelectric material to store information in a nonvolatile (NV) fashion but with the added advantage of allowing for nondestructive readout. This nondestructive readout is a result of information being stored in our cell...

Jiangang Zhu - One of the best experts on this subject based on the ideXlab platform.

  • magnetoresistive random access memory the path to competitiveness and scalability
    Proceedings of the IEEE, 2008
    Co-Authors: Jiangang Zhu
    Abstract:

    This paper provides an in-depth review of the magnetoresistive random access memory technology and its developments over the past decade. Both the traditional field-driven and more recent spin torque transfer driven designs are discussed. By pointing out key technical challenges, important aspects and characteristics of various designs are used to illustrate mechanisms that overcome the technical obstacles. A significant portion of this paper is devoted to the principles of various designs based on spin torque transfer effect, including memory elements with in-plane and perpendicular magnetic electrodes.

  • ultrahigh density vertical magnetoresistive random access memory invited
    Journal of Applied Physics, 2000
    Co-Authors: Jiangang Zhu, Youfeng Zheng, G A Prinz
    Abstract:

    In this paper, we present the vertical magnetoresistive random access memory (VMRAM) design based on micromagnetic simulation analysis. The design utilizes the vertical giant magnetoresistive effect of the magnetic multilayer. By making the memory element into a ring-shaped magnetic multilayer stack with orthogonal paired word lines, magnetic switching of the memory device becomes very robust. The design also adopts the readback scheme in pseudo spin valve MRAM so that only one transistor is needed for each bit line which can connect hundreds of memory elements, yielding a very high area density. It is estimated that the ultimate area density for the VMRAM is 400 Gbits/in.2. It is suggested that this memory design has the potential to not only replace the present semiconductor memory devices, such as FLASH, but also the potential to replace DRAM, SRAM, and even disk drives.

H Philip S Wong - One of the best experts on this subject based on the ideXlab platform.

  • optoelectronic resistive random access memory for neuromorphic vision sensors
    Nature Nanotechnology, 2019
    Co-Authors: Feichi Zhou, Jin-feng Kang, Zheng Zhou, Jiewei Chen, Tsz Hin Choy, Jingli Wang, Ning Zhang, Ziyuan Lin, H Philip S Wong, Yang Chai
    Abstract:

    Neuromorphic visual systems have considerable potential to emulate basic functions of the human visual system even beyond the visible light region. However, the complex circuitry of artificial visual systems based on conventional image sensors, memory and processing units presents serious challenges in terms of device integration and power consumption. Here we show simple two-terminal optoelectronic resistive random access memory (ORRAM) synaptic devices for an efficient neuromorphic visual system that exhibit non-volatile optical resistive switching and light-tunable synaptic behaviours. The ORRAM arrays enable image sensing and memory functions as well as neuromorphic visual pre-processing with an improved processing efficiency and image recognition rate in the subsequent processing tasks. The proof-of-concept device provides the potential to simplify the circuitry of a neuromorphic visual system and contribute to the development of applications in edge computing and the internet of things.

  • a compact model for metal oxide resistive random access memory with experiment verification
    IEEE Transactions on Electron Devices, 2016
    Co-Authors: Zizhen Jiang, Lin Yang, Kay Song, Zia Karim, H Philip S Wong
    Abstract:

    A dynamic Verilog-A resistive random access memory (RRAM) compact model, including cycle-to-cycle variation, is developed for circuit/system explorations. The model not only captures dc and ac behavior, but also includes intrinsic random fluctuations and variations. A methodology to systematically calibrate the model parameters with experiments is presented and illustrated with a broad set of experimental data, including multilayer RRAM. The physical meanings of the various model parameters are discussed. An example of applying the RRAM cell model to a ternary content-addressable-memory (TCAM) macro is provided. Tradeoffs on the design of RRAM devices for the TCAM macro are discussed in the context of the energy consumption and worst case latency of the memory array.

  • compact modeling of conducting bridge random access memory cbram
    IEEE Transactions on Electron Devices, 2011
    Co-Authors: H Philip S Wong
    Abstract:

    A physics-based compact device model is developed for the conducting-bridge random-access memory (CBRAM). By considering the dependence of ion migration velocity on the electric field, the vertical and lateral growth/dissolution dynamics for the metallic filament are investigated. Both time-dependent transient and “quasi-static” switching characteristics of the CBRAM are captured. Moreover, the I-V characteristics of the CBRAM can be reproduced. By further considering the compliance effect on the size of the metallic filament, the on-state resistance modulation is fitted, and the multilevel capability is included in the model. This model is verified by the experiments data from the Ag/Ge0.3Se0.7-based CBRAM cells. This model reveals that experimentally measured switching parameters such as the threshold voltage and the cell resistance are dynamic quantities that depend on the programming duration time. The time-dependent switching process of the CBRAM is quantified, thus paving the way for a compact SPICE model for circuit simulation.