A two-terminal binary HfO2 resistance switching random access memory for an artificial synaptic device

In this study, we developed an artificial synaptic device based on the HfO2 nanocrystals synthesized using a simple hydrothermal method. The metal–insulator–metal (MIM) structure device is designed and fabricated by combining a ceramic-like preparation technique and a standard electrode preparation method. The MIM device shows robust bipolar resistance switching characteristics with high endurance and long retention. High concentration hafnium vacancies are determined, and the formation/rupture of the conductive filament model is proposed to be responsible for the switching behavior between a high resistance state (HRS) and a low resistance state (LRS). In addition, the artificial synaptic device is simulated by applying an external pulse signal with different repetition rates and pulse widths, which exhibits synaptic functions of short term plasticity and long term plasticity. This study demonstrates that HfO2 with abundant hafnium vacancies is a potential prototype material that can be fabricated as an artificial synaptic device for mimicking the synapse of the human brain.