Effect of Top Electrode Work Function on Switching and Synaptic Characteristics of HfO₂/ZnO-based Memristive Device

This study investigates effect of the top electrode material on the resistive switching and synaptic properties of HfO₂/ZnO-based memristive devices. By varying the TE materials (Pd, Ti, TiN, and TiAu), we analyzed influence of the work function difference between top and bottom electrodes on electrical performance. Devices with a larger work function difference exhibited lower forming and set voltages, which is attributed to the enhanced internal electric field. Despite this, all of the devices showed similar conduction mechanisms, with the Ti device demonstrating gradual reset behavior due to its low Gibbs free energy. Synaptic characteristics including long-term potentiation (LTP) and long-term depression (LTD) were evaluated using a pulse scheme, that confirmed stable analog conductance modulation. These results suggest that selecting an appropriate TE material can improve switching efficiency as well as synaptic reliability of the memristive devices.