Fig. 3 (a) PPF function under a pair of positive pulses (5.5 V, 10
ms). (b) short-term plasticity after removing the operating pulse.
Pair-pulse facilitation (PPF) is an important short-term synaptic
function involved in several neuronal tasks, such as reinforcement
learning and information filtering [7]. Fig. 3a shows the
experimental demonstration of PPF function in the proposed Pt/HZO/TiN
device. When a pair of pulses (5.5 V, 10 ms) was applied to the device,
the response current gradually increased during the positive bias, and
the maximum response current of the second pulse was clearly larger than
the first one. But the current at the beginning of the second pulse is
obviously smaller than that at the ending of the first pulse, which
means a decay during the pulse interval. Fig. 3b further shows
the short-term plasticity of the self-rectifying device. After removing
the operation pulse (5.5 V, 10 ms), the device state can be maintained
for about 7 ms, monitoring by the 3 V bias voltage. Thus, the short-term
plasticity can also also be realized in Pt/HZO/TiN device.