Volatile and Nonvolatile Memory Operations Implemented in a Pt/HfO₂/Ti Memristor

Both nonvolatile and volatile characteristics are realized in the same Pt/HfO₂/Ti memristor by specific electrical operations. The resistance states of nonvolatile memory hardly change for over 10⁵ s, whereas the low resistance state of volatile memory is unstable, and degenerates gradually into the high resistance state in hundreds of seconds. The volatile device was forming-free and realized only in clockwise voltage sweeping. Compared to the nonvolatile device, the operating current of volatile device was lower and showed obviously rectification characteristics. Emulations of synaptic plasticity including short-term plasticity, long-term plasticity, and spike-time-dependent-plasticity were achieved. Finally, the resistive switching mechanism of the volatile device was analyzed and assumed to be the trapping and detrapping of electrons by traps near the interface of Pt/HfO₂.