We present a topological framework that provides a simple yet powerful electronic circuit architecture for constructing and using multilayer crossbar arrays, allowing a significantly increased ...integration density of memristive crosspoint devices beyond the scaling limits of lateral feature sizes. The truly remarkable feature of such circuits, which is an extension of the CMOL (Cmos + MOLecular-scale devices) concept for an area-like interface to a three-dimensional system, is that a large-feature-size complimentary metal-oxide-semiconductor (CMOS) substrate can provide high-density interconnects to multiple crossbar layers through a single set of vertical vias. The physical locations of the memristive devices are mapped to a four-dimensional logical address space such that unique access from the CMOS substrate is provided to every device in a stacked array of crossbars. This hybrid architecture is compatible with digital memories, field-programmable gate arrays, and biologically inspired adaptive networks and with state-of-the-art integrated circuit foundries.
AFM image of 17 nanodevices with a zoom‐in cartoon schematically shows an individual crosspoint device consisting of two Pt metal electrodes separated by a TiO2 bi‐layer memristive material. By ...applying an electric field across the memristive material, oxygen vacancies can drift up and down, leading to four current‐transport end‐states. The switching between these end‐states results in a family of nanodevices.
A breakthrough in in-memory computing technologies hinges on the development of appropriate material platforms that can overcome their existing limitations, such as larger than optimal footprint and ...multiple serial computational steps, with potential accumulation of errors. Using a molecular switching element with multiple non-monotonic and deterministic transitions, the device count and the number of computational steps can be substantially reduced. With molecular materials, however, the realization of a reliable and robust platform is an unattained goal for decades. Here, crossbar arrays with up to 64 molecular memristors are fabricated to experimentally demonstrate 8-bit serial and 4-bit parallel adders that operate for thousands of measurement cycles with an estimated error probability of 10
. For performance benchmarking, a 32-bit parallel adder is designed and simulated with 268 million inputs including contributions from the peripheral circuitry showing a 47× higher energy efficiency, 93× faster operation, and 9% of the footprint, leading to 4390 times improved energy-delay product compared to a special purpose complementary metal-oxide-semiconductor (CMOS)-based multicore adder.
Tantalum oxide memristors can switch continuously from a low-conductance semiconducting to a high-conductance metallic state. At the boundary between these two regimes are quantized conductance ...states, which indicate the formation of a point contact within the oxide characterized by multistable conductance fluctuations and enlarged electronic noise. Here, we observe diverse conductance-dependent noise spectra, including a transition from 1/f(2) (activated transport) to 1/f (flicker noise) as a function of the frequency f, and a large peak in the noise amplitude at the conductance quantum GQ=2e(2)/h, in contrast to suppressed noise at the conductance quantum observed in other systems. We model the stochastic behaviour near the point contact regime using Molecular Dynamics-Langevin simulations and understand the observed frequency-dependent noise behaviour in terms of thermally activated atomic-scale fluctuations that make and break a quantum conductance channel. These results provide insights into switching mechanisms and guidance to device operating ranges for different applications.
A synaptic transistor is fabricated by integrating ionic/electronic hybrid materials to emulate biological synapses with spike signal processing, learning, and memory functions. A potential spike ...generates transient ionic fluxes in a polymer layer in the transistor gate, triggering an excitatory postsynaptic current in the transistor drain. Temporally correlated pre‐ and post‐synaptic spikes modify ions stored in the polymer, resulting in the nonvolatile modification of the transistor with spike‐timing‐dependent plasticity.
We recently demonstrated that Mott memristors, two-terminal devices that exhibit threshold switching via an insulator to conductor phase transition, can serve as the active components necessary to ...build a neuristor, a biomimetic threshold spiking device. Here we extend those results to demonstrate, in simulation, neuristor-based circuits capable of performing general Boolean logic operations. We additionally show that these components can be used to construct a one-dimensional cellular automaton, rule 137, previously proven to be universal. This proof-of-principle shows that localized phase transitions can perform spiking computation, which is of particular interest for neuromorphic hardware.
Simple and rapid detection of trace amounts of melamine in milk products has been achieved with a portable sensor system based on surface-enhanced Raman scattering (SERS). The sensor system comprised ...high-performance gold nanofinger SERS sensor chips and a custom-built prototype portable Raman spectrometer. Compared to the FDA procedure and previously reported studies that were limited to laboratory settings, our sampling and analytical methods are simple (with one sampling step), less time-consuming, and cost-effective. We found the limit of detection (LOD) of the melamine is 120 parts per trillion (ppt) in water and 100 parts per billion (ppb) in infant formula, which are well below the FDA’s tolerance level of 1 ppm in infant formula.
A novel Ag/oxide‐based threshold switching device with attractive features including ≈1010 nonlinearity is developed. High‐resolution transmission electron microscopic analysis of the nanoscale ...crosspoint device suggests that elongation of an Ag nanoparticle under voltage bias followed by spontaneous reformation of a more spherical shape after power off is responsible for the observed threshold switching.
Abstract
The impact of a series resistor (R
S
) on the variability and endurance
performance of memristor was studied in the TaO
x
memristive system. A
dynamic voltage divider between the R
S
and ...memristor during both the set
and the reset switching cycles can suppress the inherent irregularity of the voltage
dropped on the memristor, resulting in a greatly reduced switching variability. By
selecting the proper resistance value of R
S
for the set and reset cycles
respectively, we observed a dramatically improved endurance of the TaO
x
memristor. Such a voltage divider effect can thus be critical for the memristor
applications that require low variability, high endurance and fast speed.
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