Many metal–insulator–metal systems show electrically induced resistive switching effects and have therefore been proposed as the basis for future non-volatile memories. They combine the advantages of Flash and DRAM (dynamic random access memories) while avoiding their drawbacks, and they might be highly scalable. Here we propose a coarse-grained classification into primarily thermal, electrical or ion-migration-induced switching mechanisms. The ion-migration effects are coupled to redox processes which cause the change in resistance. They are subdivided into cation-migration cells, based on the electrochemical growth and dissolution of metallic filaments, and anion-migration cells, typically realized with transition metal oxides as the insulator, in which electronically conducting paths of sub-oxides are formed and removed by local redox processes. From this insight, we take a brief look into molecular switching systems. Finally, we discuss chip architecture and scaling issues.

http://chialvo.org/Curso/UBACurso/DIA7/Papers/Aono_NatMat_07_Ionic%20Switching%20Memory.pdf

Nanoionics-based resistive switching memories

Redox‐Based Resistive Switching Memories – Nanoionic Mechanisms, Prospects, and Challenges

Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

Memristive devices are electrical resistance switches that can retain a state of internal resistance based on the history of applied voltage and current. These devices can store and process information, and offer several key performance characteristics that exceed conventional integrated circuit technology. An important class of memristive devices are two-terminal resistance switches based on ionic motion, which are built from a simple conductor/insulator/conductor thin-film stack. These devices were originally conceived in the late 1960s and recent progress has led to fast, low-energy, high-endurance devices that can be scaled down to less than 10 nm and stacked in three dimensions. However, the underlying device mechanisms remain unclear, which is a significant barrier to their widespread application. Here, we review recent progress in the development and understanding of memristive devices. We also examine the performance requirements for computing with memristive devices and detail how the outstanding challenges could be met.

Memristive devices for computing

Despite much progress in semiconductor integrated circuit technology, the extreme complexity of the human cerebral cortex, with its approximately 10(14) synapses, makes the hardware implementation of neuromorphic networks with a comparable number of devices exceptionally challenging. To provide comparable complexity while operating much faster and with manageable power dissipation, networks based on circuits combining complementary metal-oxide-semiconductors (CMOSs) and adjustable two-terminal resistive devices (memristors) have been developed. In such circuits, the usual CMOS stack is augmented with one or several crossbar layers, with memristors at each crosspoint. There have recently been notable improvements in the fabrication of such memristive crossbars and their integration with CMOS circuits, including first demonstrations of their vertical integration. Separately, discrete memristors have been used as artificial synapses in neuromorphic networks. Very recently, such experiments have been extended to crossbar arrays of phase-change memristive devices. The adjustment of such devices, however, requires an additional transistor at each crosspoint, and hence these devices are much harder to scale than metal-oxide memristors, whose nonlinear current-voltage curves enable transistor-free operation. Here we report the experimental implementation of transistor-free metal-oxide memristor crossbars, with device variability sufficiently low to allow operation of integrated neural networks, in a simple network: a single-layer perceptron (an algorithm for linear classification). The network can be taught in situ using a coarse-grain variety of the delta rule algorithm to perform the perfect classification of 3 × 3-pixel black/white images into three classes (representing letters). This demonstration is an important step towards much larger and more complex memristive neuromorphic networks.

Training and operation of an integrated neuromorphic network based on metal-oxide memristors

A resistance-variable element as disclosed has high reliability, high densification, and good insulating properties. The device provides a resistance-variable element in which a first electrode including a metal primarily containing copper, an oxide film of valve-metal, an ion-conductive layer containing oxygen and a second electrode are laminated in this order.

Resistance-variable element and method for manufacturing the same

Schalteinrichtung mit festelektrolyt, fpga damit, speicherbaustein und verfahren zur herstellung einer schalteinrichtung mit festelektrolyt

The purpose of the present invention is to enable manufacture of a metal-precipitating resistance changing element in which variations in program voltage and high-resistance-state leak current are decreased while decreasing the program voltage. The resistance changing element of the present invention comprises: a first insulating film disposed on a semiconductor substrate having a transistor formed therein; first and second electrodes which are embedded in the first insulating film and which supply metal ions; a second insulating film covering the first insulating film and the first and second electrodes; first and second opening portions which expose a part of upper surfaces of the first and second electrodes including end portions thereof from the second insulating film while having translation symmetry; metal-precipitating first and second resistance changing films which respectively cover the first and second opening portions and which are connected, in the opening portions, to the part of the upper surfaces of the first and second electrodes including the end portions; third and fourth electrodes respectively connected to the upper surfaces of the first and second resistance changing films; and a fifth electrode connected to the third and fourth electrodes and to a diffusion layer of the transistor.

Resistance changing element, method for manufacturing same, and semiconductor device

A programmable logic circuit that, to reduce the propagation delay and electromigration that can occur, depending on the number of fan-outs, in a crossbar switch circuit that uses a variable resistance element, comprises: a crossbar switch that is configured from a plurality of first wires that are arranged in a first direction, a plurality of second wires that are arranged in a second direction that intersects the first direction, and a variable resistance element that connects the first wires and the second wires; a logic circuit group that is configured from at least one logic circuit that is connected to outputs of the second wires; and an output buffer group that is configured from at least two output buffers that are connected to inputs of the first wires and operate at different drive powers

Programmable integrated circuit and control device

It is well known that the AC voltage gain of a symmetric single electron transistor amplifier has a 180° phase shift whenever the equilibrium charge in the Coulomb island changes by e/2. Using this interesting phase shift property, we propose a single electron digital phase modulation scheme. We show that there is a trade-off between the intrinsic operating speed and the voltage gain of the modulator. We show that even though the two tunnel junctions of the modulator are not matched, there is no distortion in the output signal.

Toshitsugu Sakamoto

Papers

Resistance-variable element and method for manufacturing the same

Schalteinrichtung mit festelektrolyt, fpga damit, speicherbaustein und verfahren zur herstellung einer schalteinrichtung mit festelektrolyt

Resistance changing element, method for manufacturing same, and semiconductor device

Programmable integrated circuit and control device

Single Electron Digital Phase Modulator