Nondestructive Memory Research Articles

A memristive-photoconductive transduction methodology for accurately nondestructive memory readout

Crossbar resistive memory architectures enable high-capacity storage and neuromorphic computing, accurate retrieval of the stored information is a prerequisite during read operation. However, conventional electrical readout normally suffer from complicated process, inaccurate and destructive reading due to crosstalk effect from sneak path current. Here we report a memristive-photoconductive transduction (MPT) methodology for precise and nondestructive readout in a memristive crossbar array. The individual devices present dynamic filament form/fuse for resistance modulation under electric stimulation, which leads to photogenerated carrier transport for tunable photoconductive response under subsequently light pulse stimuli. This coherent signal transduction can be used to directly detect the memorized on/off states stored in each cell, and a prototype 4 * 4 crossbar memories has been constructed and validated for the fidelity of crosstalk-free readout in recall process.

High-Tc Superconducting Memory Cell

In this paper, operational principles of a cryogenic memory cell that utilizes high-temperature superconductors (high-Tc) are presented. Such a cell consists of three inductively coupled Josephson junctions coupled via inductors. Design and operational logic of this type of cell were recently introduced and demonstrated for low temperature 4 K environment. The basic memory cell operations (read, write, reset) can be implemented on the same simple circuit and both destructive and non-destructive memory cell operations can be realized. Here, we present the design principles and computational validation of basic memory cell operations (write, read, and reset) for the high-Tc memory cell. Our results for the high-Tc memory cell operations show very good resemblance with the previously presented low-temperature 4 K memory cell operations.

Emergence of Objective Reality in an Irreversible Friend Thought Experiment

Recently some photon models of a Wigner’s friend experiment have led investigators to suggest that objective reality does not exist, and to publish articles with such claims. The public is not equipped to evaluate the severe limitations of these experiments. The separation of Wigner from the experiment and use of only reversible coherent processes for the friend allow operations that are not possible in ordinary reality according to the latest quantum research. We suggest directly testing the implied claim that objective reality, including incoherent objects with irreversible non-destructive memory, can be held in superposition. We suspect that it will fail, but provide for a graduated approach that may discover something about the conditions for superposition collapse. To this end, we design a thought experiment to model the objective world, investigating under what conditions experimenters in the same world (ensemble member) will be able to record a result and find it does not appear to change. This is not an investigation of hidden variables. To model the objective world, incoherent and irreversible processes must be included. To test for superposition, coherence has to be established. These seem to present a contradiction. The thought experiment suggests new places to look other than size for the origin of objective reality, casts doubt on the Many-Worlds interpretation, and provides a method of testing it.

Ferroelectric photovoltaic response to structural transformations in doped BiFeO3 derivative thin films

We report an investigation on crystallographic texturing, optical bandgap modulation and ferroelectric photovoltaic (FE-PV) response of semitransparent Au/BiFeO3 derivatives/Sn:In2O3 (ITO) thin film capacitors. Optimized A/B-site doping of respective Ce3+ and Mn2+ drives large-amplitude structural changes in BiFeO3 (BFO) films with partial tetragonal transformation and upsurge in extent of texture of (110) preferred orientation. Spin coated BFO, doped BiFe0.9Mn0.1O3, Bi0.88Ce0.12FeO3 and codoped Bi0.88Ce0.12Fe0.9Mn0.1O3 films of 350nm thickness on ITO coated corning glass exhibited optical transmittance of 65–80% in visible light range and revealed blue shift in optical band gap from 2.53 to 2.81eV due to splitting of t2g and eg orbital. Influence of single and co-doping on FE-PV response demonstrated crystallographic orientation and depolarizing field dependent behavior of short circuit current (JSC) and open circuit voltage (VOC). Current-voltage (J-V) characteristics of semitransparent Au/Bi0.88Ce0.12Fe0.9Mn0.1O3/ITO capacitors possessed large JON/JOFF ratio of approx. 104 at zero bias. Temporal dependence of photocurrent showed highly repeatable and stable response for consecutive ON/OFF cycles of illumination under solid state violet laser (405nm) of 160mW/cm2 intensity, a forward step towards non-destructive memory combining electronic and optical functionalities.

Nondestructive RAM Testing by Analyzing the Output Data for Symmetry

For the nondestructive march memory testing based on the symmetry analysis of the read out flows of output data, consideration was given to the conditions for manifestation of the bit-stuck, transition, and coupling faults and to construction of algorithms providing their hundred-percent covering by a minimum-complexity test and its minimum-complexity hardware realization.

Design and component test of RSFQ packet decoders for shift register memories

We show a design framework of shift register memories, which is usable for the high-speed register file of the RSFQ microprocessor. The proposed shift register memory consists of an array of shift registers and a packet decoder that switches a high-speed serial data stream into the destined shift register. A target clock frequency is 20 GHz assuming 1 kA/cm 2 Nb standard process. A concept of data-drive self-timing (DDST) is employed to reduce the timing difficulty in the synchronized RSFQ circuit. In this paper we also show the design details of the DDST RSFQ packet decoder, which is composed of one-to-two DDST RSFQ packet switches. A D3 flip-flop, a main building element of the one-to-two DDST RSFQ packet switch, is newly developed as a non-destructive memory cell. The low speed test shows that the DC bias margin of the D3 flip-flop is ±32%. We have also estimated the latency and the circuit area of the DDST packet decoder.

Memory characteristics of Au/PZT/BIT/p-Si ferroelectric diode

A ferroelectric memory diode consisting of Au/PZT/BIT/p-Si multilayer configuration has been fabricated by pulsed laser deposition (PLD) technique. The ferroelectric properties and the memory characteristics are investigated. The P-E curve of the PZT/BIT/p-Si films system had an asymmetry saturated hysteresis loop withP t=15 μC/cm2 andE c=48 kV/cm, and the decay in remanent polarization was only 10% after 109 switching cycles, meanwhile the increase in coercive field was 12%. The C-V hysteresis loop and the I-V curve showed a memory effect derived from the ferroelectric polarization of PZT/BIT films, and the current density was 6.7×10−8 A/cm2 at a voltage of +4V. Our diode had nonvolatile and nondestructive memory readout operation. There was a read current disparity of 0.05 μA for logic “1” and logic “0” at a read voltage of +2V, and the stored logical value (“1” or “0”) could be read out in 30 min.

Fabrication and characteristics of Au/PZT/BIT/p-Si ferroelectric memory diode

A ferroelectric memory diode that consisted of Au/PZT/BIT/p-Si multilayer configuration was fabricated. The Pb(Zr 0.52Ti 0.48)O 3 (PZT) ferroelectric films with a c-axis oriented Bi 4Ti 3O 12 (BIT) buffer layer were deposited on a p-Si(1 0 0) substrate by pulsed laser deposition technique. The ferroelectric characteristics and the electrical characteristics were measured respectively. The results suggested that the growth of the BIT ferroelectric layer was helpful to increase the memory window and to reduce the current density by impairing the serious interaction and interdiffusion at the ferroelectric/Si interface. The C–V hysteresis loop showed a memory effect due to the ferroelectric polarization of PZT/BIT films. The I–V curve was Schottky-diode-like and had a hysteresis loop due to the ferroelectric remanent polarization. We confirmed our diode had nonvolatile and nondestructive memory readout operation. After applied a writing voltage of +5 V for logic “1” and −5 V for logic “0” respectively, the reading currents were 0.1 and 0.05 μA at a reading voltage of +2 V correspondingly.

Pt/PZT/n-SrTiO3 Ferroelectric Memory Diode

We fabricated a new nonvolatile ferroelectric memory, which consists of vertical metal-ferroelectric- semiconductor diodes. Our diode has a simpler structure than an Ferroelectric Random Access Memory (FRAM) cell, and operates at a lower voltage than Metal Ferroelectric Semiconductor Field Effect Transistors (MFS-FETs) or conventional flash memories. We demonstrated the memory operation using a Pt/PZT/n- SrTiO3 diode in this work. We deposited (001)-oriented PZT on (100) 0.5 wt% Nb doped n-type SrTiO3 substrate using a laser ablation technique. The diodes had a hysteresis loop in their capacitance-voltage characteristics due to ferroelectric polarization in the PZT layer. Their current-voltage curves were Schottky-diode-like and also had a hysteresis loop due to the ferroelectric remanent polarization. We confirmed correct nonvolatile and nondestructive memory readout operation. The write voltages were -5 V to write a logic “0” and above 2.5 V to write a logic “1”. The read voltage was 0.8 V.

A 4-kbit Josephson nondestructive read-out RAM operated at 580 psec and 6.7 mW

A fully decoded 4-kb Josephson nondestructive readout high-speed RAM with vortex transitional memory cells was designed and operated successfully. The 4-kb Josephson RAM is composed of 64-b*64-b cells, polarity-convertible drivers, address decoders using resistor coupled Josephson logic (RCJL) gates, and a resistively loaded sense circuit. The memory cells use vortex transitions in their superconducting loops for writing and reading data. The cells are activated by two control signals without timing control, while all peripheral circuits are activated by an AC power supply. This memory configuration eliminates the timing sequence needed for memory operations, resulting in a decrease in the memory operation time for an actual memory chip. The 4-kb Josephson high-speed RAM was fabricated using niobium planarization technique with a 1.5- mu m design rule. The RAM circuit size is 4.8*4.8 mm/sup 2/ and the memory cell is 55*55 mu m/sup 2/. More than 25000 Nb-AlO/sub x/-Nb Josephson junctions with approximately 1200 A/cm/sup 2/ critical current density are contained in the RAM chip. An access time of 580 ps and a power consumption of 6.7 mW are obtained for the nondestructive memory operation.

A Josephson associative memory circuit

This paper proposes a novel associative memory circuit using Josephson interferometers. This associative memory circuit is mainly constructed with the nondestructive memory cell in which a self-rewriting operation can be achieved by setting a coil between the terminals of the interferometer. The principle of the associative memory circuit is described and the results of simulation for the operation are illustrated. The results show that the cycle time of operation is less than 75ps and the design tolerance of input signals for the memory circuit is about 8%.

Nondestructive memory cell using a two-junction Josephson interferometer

This paper presents a novel nondestructive memory cell using a two-junction interferometer. Most of single-flux-quantum memory cells have been the destructive ones, which must rewrite the information for logic "1" after a reading operation. This makes the circuitry of the cell complex. To avoid this disadvantage, a novel self-rewriting technique is introduced by setting a coil between the terminals of the interferometer. The principle of the operation of the cell is described and the simulation for the behaviours of the cell are illustrated in detail. The results of the simulation show that the reliable operation of the cell can be achieved with high operating speed.

Nondestructive toroidal memory core

By metal-cladding and drawing of semihard and soft magnetic materials, a simple toroidal core which has a nondestructive memory function was developed. The nondestructive property arises from the shift of the minor loop in the composite magnetic characteristic. The shift occurs either in the first and the third quadrants, or in the second and the fourth quadrants. This toroidal core utilizes the second type of shift, which is due to the exchange force between the two magnetic materials. The information is stored by means of the remanent state of the semi-hard magnetic material, and is read out through magnetization reversal of the soft magnetic material.

THE FEEDBACK CONTROL OF SUGAR NUCLEOTIDE BIOSYNTHESIS IN LIVER.

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Fabrication of Microminiaturized Core Memories by Plastic Encapsulation Techniques

Plastic encapsulation of nonlinear ferrites, and the effect of this encapsulation on the magnetic characteristics of the ferrites, is discussed in this paper. This technique provides greater immunity to shock and vibration damage than conventional core frames and provides bit densities in excess of one million per cubic foot. Chemical deposition and photographic techniques may be used to form a portion of the wiring matrix. Through-hole plating of ferrites having a 15-mil diameter hole is possible. Small-evaluation memories have been fabricated, using both toroids and transfluxors. Temperature tests on these memories show that encapsulation causes a slight increase in switching speed and a small decrease on output for a given drive current. These changes remain almost constant over the temperature range. No significant changes have been noted in the noise output. Techniques outlined are presently being used in the fabrication of microminiaturized, nondestructive memories for missile and satellite application.

Magnetic film memories, a survey

An analysis is made of the modes of magnetization reversal and rotation in thin ferromagnetic films. The ways in which the various modes can be employed for destructive and non-destructive memories are discussed and their performance limitations considered. Existing film memory efforts are partially surveyed and the material and system problems are examined. Possible future developments are also discussed.

Electrodeposited Memory Elements for a Nondestructive Memory

Nickel-iron films are being electrodeposited on to a wire substrate to form memory elements for a fast,nondestructive memory. By plating in the presence of a directed magnetic field, an anisotropy favoring circumferential orientation is established. Axial interrogation fields cause reversible rotations of less than 90°and produce output signals across the ends of the wire. The apparatus and techniques used to make this wire are discussed together with the rationale back of the design. The choice of alloy composition and the plating conditions strongly affect the results. The amount of stress in the deposit, the residual stress in the substrate,the control of precleaning of the substrate, the use of a suitable wetting agent, and the degree of stirring in the electrolyte appear as the vital factors in obtaining consistent results. Moderate fields (∼30 oersteds)applied during plating produce a preferred circumferential orientation with high anisotropy (HK/H0 = 3.0). Squareness ratio in the easy direction is 0.99. Output signals appear during the rise time of the interrogation pulse with an amplitude inversely related to the rise time and directly proportional to the length interrogated. Very fast switching with unusually high output signals per unit length are possible. Selective write in is possible with current margins of 3:1. Preliminary investigations indicate that it would be feasible to make plated wire on a production basis with properties suitable for memory applications.

Esaki Diode High-Speed Logical Circuits

Logical circuits using Esaki diodes, and which are based on a principle similar to parametron (subharmonic oscillator element) circuits, are described. Two diodes are used in series to form a basic element called a twin, and a binary digit is represented by the polarity of the potential induced at the middle point of the twin, which is controlled by the majority of input signals applied to the middle point. Unilateral transmission of information in circuits consisting of cascaded twins is achieved by dividing the twins into three groups and by energizing each group one after another in a cyclic manner. Experimental results with the clock frequency as high as 30 mc are reported. Also, a delay-line dynamic memory and a nondestructive memory in matrix form are discussed.