Synaptic Learning and Forgetting Behavior in Ag/AlN/Al Memristor wit Annealing Effect

Abstract

The learning and forgetting behavior of AlN thin film with O2 annealing effect memristor had been investigated in this study. Such synaptic behavior could be observed after AlN thin film executed O2 annealing process. The oxygen-induced AlN thin film exhibited memristive effect in resistance with positive and negative current-voltage (I-V) measurement loops which had never been observed in AlN thin film without annealing effect. The O2 annealing process could decrease the number of oxygen vacancies ( $\text{V}_{\mathrm {o}}^{+}$ ) in interface between top electrode and active layer. A typical I-V measurement is shown in this study. If continuous positive voltage pulses applied, the device conductance would increase gradually which is called learning behavior of device. If negative voltage pulse applied, the device conductance would decrease gradually which is called forgetting behavior of device. The memristor conductance was thought to be closely associated with synaptic weights, the strength of synaptic connections. The learning and forgetting behavior of memristor is corresponding to LTP and LTD process in synaptic system. The ion diffusion played an important role in memristive properties which could form one or more local conductive filaments (CFs) in active layer. If the paths were gradually formed or broke, this would cause the memristor conductance changed gradually with measured voltage. The retention time and memristor conductance should depend on stimuli pulse shape, number and interval time.