  Synaptic devices with linear high-speed switching can accelerate learning in
artificial neural networks (ANNs) embodied in hardware. Conventional resistive
memories however suffer from high write noise and asymmetric conductance
tuning, preventing parallel programming of ANN arrays as needed to surpass
conventional computing efficiency. Electrochemical random-access memories
(ECRAMs), where resistive switching occurs by ion insertion into a redox-active
channel address these challenges due to their linear switching and low noise.
ECRAMs using two-dimensional (2D) materials and metal oxides suffer from slow
ion kinetics, whereas organic ECRAMs enable high-speed operation but face
significant challenges towards on-chip integration due to poor temperature
stability of polymers. Here, we demonstrate ECRAMs using 2D titanium carbide
(Ti3C2Tx) MXene that combines the high speed of organics and the integration
compatibility of inorganic materials in a single high-performance device. Our
ECRAMs combine the speed, linearity, write noise, switching energy and
endurance metrics essential for parallel acceleration of ANNs, and importantly,
they are stable after heat treatment needed for back-end-of-line integration
with Si electronics. The high speed and performance of these ECRAMs introduces
MXenes, a large family of 2D carbides and nitrides with more than 30
compositions synthesized to date, as very promising candidates for devices
operating at the nexus of electrochemistry and electronics.
