Non-filamentary Pd/Al2O3/TaOx/Ta Memristor as Artificial Synapse for Neuromorphic Computing

We report a fully CMOS compatible bilayer, forming-free and non-filamentary memristive device with excellent bidirectional analog switching behavior as artificial synapse for neuromorphic computing applications. The bilayer stack structure, consisting of 8 nm TaO
_x
formed via oxidation process on Ta bottom electrode and 7 nm Al
₂
O
₃
via atom layer deposition (ALD), is sandwiched between the Ta bottom electrode and Pd top electrode. The Pd/Al
₂
O
₃
/TaO
_x
/Ta device shows bidirectional analog resistive switching behaviors, and multilevel conductance states (>60) with satisfying retention time can be obtained. Long term plasticity, consisting of long-term potentiation (LTP) and long-term depression (LTD), have been demonstrated based our device. And a nearly linear conductance change behavior is obtained by optimizing the training scheme: adopting non-identical training pulses.A two-layer perceptron neural networkwas performed to estimate the synapse characteristics of our devices. More than 94% recognition accuracy of MNIST handwritten digit dataset are achieved. Based on these results, the device is a promising emulator for biology synapse, and has a great potential to be used in neuromorphic systems.