RESUMEN
The understanding of magnetoresistance (MR) in organic spin valves (OSVs) based on molecular semiconductors is still incomplete after its demonstration more than a decade ago. Although carrier concentration may play an essential role in spin transport in these devices, direct experimental evidence of its importance is lacking. We probed the role of the charge carrier concentration by studying the interplay between MR and multilevel resistive switching in OSVs. The present work demonstrates that all salient features of these devices, particularly the intimate correlation between MR and resistance, can be accounted for by the impurity band model, based on oxygen migration. Finally, we highlight the critical importance of the carrier concentration in determining spin transport and MR in OSVs and the role of interface-mediated oxygen migration in controlling the OSV response.
RESUMEN
Potential advantages of analog- and mixed-signal nanoelectronic circuits, based on floating-gate devices with adjustable conductance, for neuromorphic computing had been realized long time ago. However, practical realizations of this approach suffered from using rudimentary floating-gate cells of relatively large area. Here, we report a prototype $28\times28$ binary-input, ten-output, three-layer neuromorphic network based on arrays of highly optimized embedded nonvolatile floating-gate cells, redesigned from a commercial 180-nm nor flash memory. All active blocks of the circuit, including 101 780 floating-gate cells, have a total area below 1 mm2. The network has shown a 94.7% classification fidelity on the common Modified National Institute of Standards and Technology benchmark, close to the 96.2% obtained in simulation. The classification of one pattern takes a sub-1- $\mu \text{s}$ time and a sub-20-nJ energy-both numbers much better than in the best reported digital implementations of the same task. Estimates show that a straightforward optimization of the hardware and its transfer to the already available 55-nm technology may increase this advantage to more than $10^{2}\times $ in speed and $10^{4}\times $ in energy efficiency.
RESUMEN
Nanoparticles (NPs) embedded in a conductive or insulating matrix play a key role in memristors and in flash memory devices. However, the role of proximity to the interface of isolated NPs has never been directly observed nor fully understood. Here we show that a reversible local switching in tunnel conductivity can be achieved by applying an appropriate voltage pulse using the tip of a scanning tunnelling microscope on NPs embedded in a TiO2 matrix. The resistive switching occurs in the TiO2 matrix in correlation to the NPs that are in proximity of the surface and it is spatially confined to the single NP size. The tunnel conductivity is increased by more than one order of magnitude. The results are rationalized by a model that include the charge of NPs that work as a nano floating gate inducing local band bending that facilitates charge tunnelling and by the formation and redistribution of oxygen vacancies that concentrate in proximity of the charged NPs. Our study demonstrates the switching in tunnel conductivity in single NP and provides useful information for the understanding mechanism or resistive switching.
RESUMEN
Memristors are one of the most promising candidates for future information and communications technology (ICT) architectures. Two experimental proofs of concept are presented based on the intermixing of spintronic and memristive effects into a single device, a magnetically enhanced memristor (MEM). By exploiting the interaction between the memristance and the giant magnetoresistance (GMR), a universal implication (IMP) logic gate based on a single MEM device is realized.
RESUMEN
A nanomemristor based on SiO(2) is fabricated in situ with spatial control at the nanoscale. The proposed system exhibits peculiar properties such as the possibility to be regenerated after being stressed or damaged and the possibility to expose the metal and the oxide interfaces by removing the top electrodes.