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

We report on a microfluidic particle-separation device that makes use of the asymmetric bifurcation of laminar flow around obstacles. A particle chooses its path deterministically on the basis of its size. All particles of a given size follow equivalent migration paths, leading to high resolution. The microspheres of 0.8, 0.9, and 1.0 micrometers that were used to characterize the device were sorted in 40 seconds with a resolution of approximately 10 nanometers, which was better than the time and resolution of conventional flow techniques. Bacterial artificial chromosomes could be separated in 10 minutes with a resolution of approximately 12%.

http://science.sciencemag.org/content/sci/304/5673/987.full.pdf

Continuous Particle Separation Through Deterministic Lateral Displacement

We describe a nanometer-scale switch that uses a copper sulfide film and demonstrate its performance. The switch consists of a copper sulfide film, which is a chalcogenide semiconductor, sandwiched between copper and metal electrodes. Applying a positive or negative voltage to the metal electrode can repeatedly switch its conductance in under 100 μs. Each state can persist without a power supply for months, demonstrating the feasibility of nonvolatile memory with its nanometer scale. While biasing voltages, copper ions can migrate in copper sulfide film and can play an important role in switching.

Nanometer-scale switches using copper sulfide

A reconfigurable LSI employing a nonvolatile nanometer-scale switch, NanoBridge, is proposed, and its basic operations are demonstrated. The switch, composed of solid electrolyte copper sulfide, has a <30-nm contact diameter and <100-/spl Omega/ on-resistance. Because of its small size, it can be used to create extremely dense field-programmable logic arrays. A 4 /spl times/ 4 crossbar switch and a 2-input look-up-table circuit are fabricated with 0.18-/spl mu/m CMOS technology, and operational tests with them have confirmed the switch's potential for use in programmable logic arrays. A 1-kb nonvolatile memory is also presented, and its potential for use as a low-voltage memory device is demonstrated.

A nonvolatile programmable solid electrolyte nanometer switch

We investigated quantum mechanical effects in electrically variable shallow junction metal–oxide–semiconductor field-effect transistors with an 8 nm long gate. We clearly observed the direct tunneling current from the source to the drain below 77 K, in good agreement with the calculation. We also showed that the direct tunneling current will exceed the thermal current and will become detrimental to low-voltage operation of MOSLSIs in the 5 nm gate generation.

Observation of source-to-drain direct tunneling current in 8 nm gate electrically variable shallow junction metal–oxide–semiconductor field-effect transistors

The present invention provides a solid electrolyte switching device, which can maintain an on or off state when the power source is removed, the resistance of which in on the state is low, and which is capable of integration and re-programming, and FPGA and a memory device using the same, and a method of manufacturing the same. A solid electrolyte switching device (10, 10′, 20, 20′) comprises a substrate (11) in which surface is coated with an insulation layer, a first interconnection layer (13) set on said substrate (11), an ion supplying layer (17) set on said first interconnection layer (13), a solid electrolyte layer (16) set on said ion supplying layer (17), an interlevel insulating layer (12) having a via hole set to cover said first interconnection layer (13), said ion supplying layer (17), and said solid electrolyte layer (16), a counter electrode layer (15) set to contact said solid electrolyte layer (16) through the via hole of said interlevel insulating layer (12), and a second interconnection layer (14) set to cover said counter electrode layer (15). The switching device can be provided in which the on state, or the off state can be arbitrarily set by the threshold voltage applied between the ion supplying layer (17) and the counter electrode layer (15), which is non-volatile, and the resistance of which in the on state is low. The switching device of the present invention is also simple and fine in structure, and hence makes it possible to provide smaller switching devices than are currently available. Further, using the switching device of the present invention as the switching device of an FPGA (30) makes it possible to provide re-programmable and fast operation FPGA (30). Using the switching device of the present invention as a memory cell of a memory device makes it possible to provide a non-volatile memory device with high programming and reading speed.

Solid electrolyte switching device, FPGA using same, memory device, and method for manufacturing solid electrolyte switching device

We present a novel solid-electrolyte switch ("NanoBridge") promising for application to field programmable gate array (FPGA). We replace a former solid electrolyte of Cu2S with Ta2O5, which has a Si-process compatibility, . As a result, we successfully control the turn-on voltage to adapt to CMOS operation. The Ta2O5-NanoBridge exhibits a high reliability of cycling endurance (>104) and a stability against EM (>10 years at 2.6 mA at RT). Furthermore, we demonstrate that the conducting path of the switch is a Cu precipitate with 30 nm in diameter, which possibly enables to scale down the switch.

/pdf/a-ta-2-o-5-solid-electrolyte-switch-with-improved-qahab0arx7.pdf

Hisao Kawaura

Papers

Nanometer-scale switches using copper sulfide

A nonvolatile programmable solid electrolyte nanometer switch

Observation of source-to-drain direct tunneling current in 8 nm gate electrically variable shallow junction metal–oxide–semiconductor field-effect transistors

Solid electrolyte switching device, FPGA using same, memory device, and method for manufacturing solid electrolyte switching device

A Ta 2 O 5 solid-electrolyte switch with improved reliability