Conductance quantization and synaptic behavior in a Ta ₂O ₅-based atomic switch

Quantized conductance was observed in a cation-migration-based resistive switching memory cell with a simple metalinsulatormetal (MIM) structure using a thin Ta ₂O ₅ layer. The observed conductance changes are attributed to the formation and dissolution of a metal filament with an atomic point contact of different integer multiples in the Ta ₂O ₅ layer. The results demonstrate that atomic point contacts can be realized in an oxide-based MIM structure that functions as a nanogap-based atomic switch (Terabe etal 2005 Nature 433 47). By applying consecutive voltage pulses at periodic intervals of different times, we also observed an effect analogous to the long-term potentiation of biological synapses, which shows that the oxide-based atomic switch has potential for use as an essential building block of neural computing systems.