High-precision and linear weight updates by subnanosecond pulses in ferroelectric tunnel junction for neuro-inspired computing

Abstract

The rapid development of neuro-inspired computing demands synaptic devices with ultrafast speed, low power consumption, and multiple non-volatile states, among other features. Here, a high-performance synaptic device is designed and established based on a Ag/PbZr0.52Ti0.48O3 (PZT, (111)-oriented)/Nb:SrTiO3 ferroelectric tunnel junction (FTJ). The advantages of (111)-oriented PZT (~1.2 nm) include its multiple ferroelectric switching dynamics, ultrafine ferroelectric domains, and small coercive voltage. The FTJ shows high-precision (256 states, 8 bits), reproducible (cycle-to-cycle variation, ~2.06%), linear (nonlinearity <1) and symmetric weight updates, with a good endurance of >109 cycles and an ultralow write energy consumption. In particular, manipulations among 150 states are realized under subnanosecond (~630 ps) pulse voltages ≤5 V, and the fastest resistance switching at 300 ps for the FTJs is achieved by voltages <13 V. Based on the experimental performance, the convolutional neural network simulation achieves a high online learning accuracy of ~94.7% for recognizing fashion product images, close to the calculated result of ~95.6% by floating-point-based convolutional neural network software. Interestingly, the FTJ-based neural network is very robust to input image noise, showing potential for practical applications. This work represents an important improvement in FTJs towards building neuro-inspired computing systems.

Emerging Memristive Devices for Brain-Inspired Computing and Artificial Perception

“…Multiple resistance states with bidirectional continuous reversibility can be acquired at the same time, similar to the change of synaptic weights. The ferroelectric memristive synapse has the advantages of fast read and write speed, low driving voltage, and high storage density, and it can overcome the shortcomings of the traditional resistive memristor's conductive filament instability and fracture, it has demonstrated outstanding characteristics such as high ON/OFF current ratios, high data storage density, fast switching speeds, and ultra-low power (Zucker and Regehr, 2002;Kullmann and Lamsa, 2007;Luo et al, 2022). Sayani Majumdar et al proposed a ferroelectric tunnel junction based on a spin-coated 3 nm thick ferroelectric poly (vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and realized the simulation of synaptic function (Majumdar et al, 2019), exhibiting analog switching behavior in the range of five orders of magnitude, reproducibly simulate LTP/STP, LTD/STD and STDP, in addition, the device has good stability and a large range of conductance variation.…”

High-Speed Nanoscale Ferroelectric Tunnel Junction for Multilevel Memory and Neural Network Computing

“…For example, six resistance states at an operation speed of 100 ns were obtained in Co/BiFeO 3 /Ca 0.96 Ce 0.04 MnO 3 FTJs with a diameter of 180 nm . Significantly improved ON/OFF ratio was demonstrated in metal/ferroelectric/semiconductor (MFS)-type FTJs by taking advantage of the ferroelectric field-effect-manipulated Schottky barrier at the surface of the semiconductor electrode. − When FTJs were utilized as artificial synapses, continuous manipulations among ≥200 conductance states have been achieved in FTJs with diameters ≥10 μm, and the corresponding neural network simulations exhibited high classification accuracies for handwritten digits or fashion product images. , …”

“…Thus, further investigations on properly designed nanoscale FTJs to achieve multistate memory and high-performance electronic synapse are crucial. Very recently, an Ag/PbZr 0.52 Ti 0.48 O 3 (PZT, (111)-oriented, ∼ 1.2 nm)/Nb-doped SrTiO 3 (NSTO) FTJ with a diameter of ∼100 μm has shown 256 conductance states at 10 ns . The numerous states can be attributed to the successive switching process of multiple domains by adopting thin (111)-oriented PZT film near morphotropic phase boundary.…”

A self-assembly growth strategy for a highly ordered ferroelectric nanoisland array

“…Ferroelectric materials, due to their bistable polarization, have found applications in non-volatile random-access memories, 1 ferroelectric field-effect transistors 2 and ferroelectric tunnel junctions, 3 and have also inspired intriguing possibilities in neuromorphic computing. 4,5 In particular, size/geometry-confined ferroelectric nanostructures not only promise individual addressability with their extended memory density approaching TB/inch, 2,6–8 but also exhibit exotic topological domain configurations, 9 including flux-closure quadrants, 10 center-type quad-domains, 11,12 vortex 13–15 and skyrmions, 16 all of which have received considerable attention both for their novel features ( e.g. , stable domain structures 12,14 and controllable domain wall conductance 11,17 ) and potential applications in nanoelectronic devices.…”