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Tunnel junction based memristors as artificial synapses.

Thomas A, Niehörster S, Fabretti S, Shepheard N, Kuschel O, Küpper K, Wollschläger J, Krzysteczko P, Chicca E - Front Neurosci (2015)

Bottom Line: The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use.Here, we increased the amplitude of the resistance change from 10% up to 100%.Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses.

View Article: PubMed Central - PubMed

Affiliation: Thin Films and Physics of Nanostructures, Bielefeld University Bielefeld, Germany ; IFW Dresden, Institute for Metallic Materials Dresden, Germany.

ABSTRACT
We prepared magnesia, tantalum oxide, and barium titanate based tunnel junction structures and investigated their memristive properties. The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use. Here, we increased the amplitude of the resistance change from 10% up to 100%. Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses. We observed analogs of long-term potentiation, long-term depression and spike-time dependent plasticity in these simple two terminal devices. Finally, we suggest a possible pathway of these devices toward their integration in neuromorphic systems for storing analog synaptic weights and supporting the implementation of biologically plausible learning mechanisms.

No MeSH data available.


Related in: MedlinePlus

Flux-dependent plasticity of memristive magnetic tunnel junctions. Top: The asymmetric conductivity of a memristive tunnel junction. Positive flux is associated with causal spike-timing, negative flux with anti-causal spike-timing. The asymmetry typical for stdp is evaluated by the fitting curves. Bottom: The derivative of the fitting curves in the top graph is calculated to provide a measure of the change in synaptic strength.
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Figure 4: Flux-dependent plasticity of memristive magnetic tunnel junctions. Top: The asymmetric conductivity of a memristive tunnel junction. Positive flux is associated with causal spike-timing, negative flux with anti-causal spike-timing. The asymmetry typical for stdp is evaluated by the fitting curves. Bottom: The derivative of the fitting curves in the top graph is calculated to provide a measure of the change in synaptic strength.

Mentions: The increase (decrease) in the conductivity of the junctions can be associated with long-term potentiation LTP (depression, LTD) in a biological neural network. Linares-Barranco et al. suggested to shape the pulses in a particular way (see Linares-Barranco and Serrano-Gotarredona, 2009): The increasing and decreasing edges of the pulses follow an exponential increase and decay, respectively. Two subsequent pulses can generate a positive as well as negative net flux. If we now take similar data depending on the spike-timing, we acquire the flux-dependent plasticity shown in Figure 4.


Tunnel junction based memristors as artificial synapses.

Thomas A, Niehörster S, Fabretti S, Shepheard N, Kuschel O, Küpper K, Wollschläger J, Krzysteczko P, Chicca E - Front Neurosci (2015)

Flux-dependent plasticity of memristive magnetic tunnel junctions. Top: The asymmetric conductivity of a memristive tunnel junction. Positive flux is associated with causal spike-timing, negative flux with anti-causal spike-timing. The asymmetry typical for stdp is evaluated by the fitting curves. Bottom: The derivative of the fitting curves in the top graph is calculated to provide a measure of the change in synaptic strength.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493388&req=5

Figure 4: Flux-dependent plasticity of memristive magnetic tunnel junctions. Top: The asymmetric conductivity of a memristive tunnel junction. Positive flux is associated with causal spike-timing, negative flux with anti-causal spike-timing. The asymmetry typical for stdp is evaluated by the fitting curves. Bottom: The derivative of the fitting curves in the top graph is calculated to provide a measure of the change in synaptic strength.
Mentions: The increase (decrease) in the conductivity of the junctions can be associated with long-term potentiation LTP (depression, LTD) in a biological neural network. Linares-Barranco et al. suggested to shape the pulses in a particular way (see Linares-Barranco and Serrano-Gotarredona, 2009): The increasing and decreasing edges of the pulses follow an exponential increase and decay, respectively. Two subsequent pulses can generate a positive as well as negative net flux. If we now take similar data depending on the spike-timing, we acquire the flux-dependent plasticity shown in Figure 4.

Bottom Line: The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use.Here, we increased the amplitude of the resistance change from 10% up to 100%.Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses.

View Article: PubMed Central - PubMed

Affiliation: Thin Films and Physics of Nanostructures, Bielefeld University Bielefeld, Germany ; IFW Dresden, Institute for Metallic Materials Dresden, Germany.

ABSTRACT
We prepared magnesia, tantalum oxide, and barium titanate based tunnel junction structures and investigated their memristive properties. The low amplitudes of the resistance change in these types of junctions are the major obstacle for their use. Here, we increased the amplitude of the resistance change from 10% up to 100%. Utilizing the memristive properties, we looked into the use of the junction structures as artificial synapses. We observed analogs of long-term potentiation, long-term depression and spike-time dependent plasticity in these simple two terminal devices. Finally, we suggest a possible pathway of these devices toward their integration in neuromorphic systems for storing analog synaptic weights and supporting the implementation of biologically plausible learning mechanisms.

No MeSH data available.


Related in: MedlinePlus