Biological synapses store multiple memories on top of each other in a palimpsest fashion and at different time scales. Palimpsest consolidation is facilitated by the interaction of hidden biochemical processes governing synaptic efficacy during varying lifetimes. This arrangement allows idle memories to be temporarily overwritten without being forgotten, while previously unseen memories are used in the short term. While embedded artificial intelligence can greatly benefit from this functionality, a practical demonstration in hardware is missing. Here, we show how the intrinsic properties of metal-oxide volatile memristors emulate the processes supporting biological palimpsest consolidation. Our memristive synapses exhibit an expanded doubled capacity and protect a consolidated memory while up to hundreds of uncorrelated short-term memories temporarily overwrite it, without requiring specialized instructions. We further demonstrate this technology in the context of visual working memory. This showcases how emerging memory technologies can efficiently expand the capabilities of artificial intelligence hardware toward more generalized learning memories.
Resistive RAM (RRAM) or memristors are a class of electronic device whose resistance depends on voltage history. The changes in resistance can be divided into two categories, volatile and non-volatile. To date, the characteristics of non-volatile switching have been explored extensively with volatile switching behaviour still remaining more obscure. Here we investigate the temperature effects on TiOx based memristor volatility, and integrate these observations into a previously developed model for volatile switching. We show how device temperature affects the magnitude of the volatile resistive state in response to input stimulation, as well as the corresponding relaxation time constant. Importantly, these effects are polarity dependent. This work is part of an effort towards building a more comprehensive model of RRAM behaviour covering volatile and non-volatile phenomena as well as various environmental effects on them.
This paper reports novel characteristic features of thermally-passivated Si nanoelectromechanical (NEM) beams fabricated via SOI-CMOS compatible processes with top-down hybrid EB/DUV lithography. Considerable difference of the resonance frequencies between the measurement results of the NEM beams with various lengths and the finite element simulation results suggests that effects of the undercut of the beam supports are serious for sub-micron beams. The resonance frequency of 332.57 MHz observed for an 800-nm-long beam is, to our knowledge, the highest ever as the fundamental resonance mode of lithographically-defined Si NEM beams. Clear change of the temperature dependence of the resonance frequencies with the varied beam lengths, observed for the first time, can be explained by considering effects of thermally-induced strain on the longer beams at higher temperatures.
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