In-situ impedance matching in Nb/Nb2O5/PtIr memristive nanojunctions for ultra-fast neuromorphic operation

Dániel Molnár,  Tímea Nóra Török,  Botond Sánta,  Agnes Gubicza,  András Magyarkuti,  Roland Hauert,  Gábor Kiss,  Andras Halbritter  and  Miklos Csontos 

Nanoscale, 01. Oct 2018

http://dx.doi.org/10.1039/C8NR06226A

Abstract
/documents/56066/5137854/20181001-pub-insituimpedance.png/a163f4bd-0aac-4df0-85a6-ed9a73515456?t=1539157680231
The dynamical aspects of bipolar resistive switchings have been investigated in Nb/Nb2O5/PtIr nanojunctions. We found that the widely tuneable ON and OFF state resistances are well separated at low bias. On the other hand, the high-bias regime of the resistive switchings coincides with the onset of a high nonlinearity in the current-voltage characteristics, where the impedance of both states rapidly decrease and become equivalent around 50 Ω. This phenomenon enables the overriding of the RC limitations of fast switchings between higher resistance ON and OFF states. Consequently, nanosecond switching times between multiple resistance states due to subnanosecond voltage pulses are demonstrated. Moreover, this finding opens the possibility of impedance engineering by the appropriate choice of voltage signals, which facilitate that both the set and reset transitions take place in an impedance matched manner to the surrounding circuit, demonstrating the merits of ultra-fast operation of Nb/Nb2O5 based neuromorphic networks.