**2.2 Electrical performances and synaptic functions**

The electrical properties were measured under DC sweep and pulse modes using semiconductor parameter analyzer on probe station. The bottom electrode of memristors was set on ground and all the voltage signals were applied to the top electrode. The asymmetric bilayer ultrathin memristors were exploited to mimic some important synaptic functions such as long-term potentiation/depression, the transition from STP to LTP, PPF and STDP.
