We study the resistive switching (RS) mechanism as way to obtain multi-level memory cell (MLC) devices. In a MLC more than one bit of information can be stored in each cell. Here we identify one of the main conceptual difficulties that prevented the implementation of RS-based MLCs. We present a method to overcome these difficulties and to implement a 6-bit MLC device with a manganite-based RS device. This is done by precisely setting the remnant resistance of the RS-device to an arbitrary value. Our MLC system demonstrates that transition metal oxide non-volatile memories may compete with the currently available MLCs.
This paper presents a novel resistive-only Binary and Ternary Content Addressable Memory (B/TCAM) cell that consists of two Complementary Resistive Switches (CRSs). The operation of such a cell relies on a logic$rightarrow$ON state transition that enables this novel CRS application.
The increasing demand for high-density data storage leads to an increasing interest in novel memory concepts with high scalability and the opportunity of storing multiple bits in one cell. A promising candidate is the redox-based resistive switch repositing the information in form of different resistance states. For reliable programming, the underlying physical parameters need to be understood. We reveal that the programmable resistance states are linked to internal series resistances and the fundamental nonlinear switching kinetics. The switching kinetics of Ta$_{2}$O$_{5}$-based cells was investigated in a wide range over 15 orders of magnitude from 250 ps to 10$^{5}$ s. We found strong evidence for a switching speed of 10 ps which is consistent with analog electronic circuit simulations. On all time scales, multi-bit data storage capabilities were demonstrated. The elucidated link between fundamental material properties and multi-bit data storage paves the way for designing resistive switches for memory and neuromorphic applications.
We investigate the polarity-dependent field-induced resistive switching phenomenon driven by electric pulses in perovskite oxides. Our data show that the switching is a common occurrence restricted to an interfacial layer between a deposited metal electrode and the oxide. We determine through impedance spectroscopy that the interfacial layer is no thicker than 10 nm and that the switch is accompanied by a small capacitance increase associated with charge accumulation. Based on interfacial I-V characterization and measurement of the temperature dependence of the resistance, we propose that a field-created crystalline defect mechanism, which is controllable for devices, drives the switch.
The magnetoelectric effects in multiferroics have a great potential in creating next-generation memory devices. We conceive a new concept of non-volatile memories based on a type of nonlinear magnetoelectric effects showing a butterfly-shaped hysteresis loop. The principle is to utilize the states of the magnetoelectric coefficient, instead of magnetization, electric polarization or resistance, to store binary information. Our experiments in a device made of the PMN-PT/Terfenol-D multiferroic heterostructure clearly demonstrate that the sign of the magnetoelectric coefficient can be repeatedly switched between positive and negative by applying electric fields, confirming the feasibility of this principle. This kind of non-volatile memory has outstanding practical virtues such as simple structure, easy operations in writing and reading, low power, fast speed, and diverse materials available.
The field-effect-induced modulation of transport properties of 2-dimensional electron gases residing at the LaAlO$_3$/SrTiO$_3$ and LaGaO$_3$/SrTiO$_3$ interfaces has been investigated in a back-gate configuration. Both samples with crystalline and with amorphous overlayers have been considered. We show that the naive standard scenario, in which the back electrode and the 2-dimensional electron gas are simply modeled as capacitor plates, dramatically fails in describing the observed phenomenology. Anomalies appearing after the first low-temperature application of a positive gate bias, and causing a non-volatile perturbation of sample properties, are observed in all our samples. Such anomalies are shown to drive low-carrier density samples to a persistent insulating state. Recovery of the pristine metallic state can be either obtained by a long room-temperature field annealing, or, instantaneously, by a relatively modest dose of visible-range photons. Illumination causes a sudden collapse of the electron system back to the metallic ground state, with a resistivity drop exceeding four orders of magnitude. The data are discussed and interpreted on the base of the analogy with floating-gate MOSFET devices, which sheds a new light on the effects of back-gating on oxide-based 2-dimensional electron gases. A more formal approach, allowing for a semi-quantitative estimate of the relevant surface carrier densities for different samples and under different back-gate voltages, is proposed in the Appendix.
P. Stoliar
,P. Levy
,M. J. Sanchez
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(2013)
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"Non-volatile multilevel resistive switching memory cell: A transition metal oxide-based circuit"
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Pablo Stoliar
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