Application of the Quantum-Point-Contact Formalism to Model the Filamentary Conduction in Ta2O5-Based Resistive Switching Devices

Redox-based resistive random access memories (ReRAMs) are promising candidate devices for new memory and computing paradigms. However, the fundamental mechanisms that rule the conduction in these devices are still heavily debated. The present work focuses on studying one model for the conduction, the quantum point contact (QPC), and specifically a single-subband approximation (SSA) to this model. With this intent, Pt(20 nm)/Ta(15 nm)Ta2O5(5 nm)/Pt(20 nm) resistive switching devices are fabricated and electrically characterized by measuring current-voltage (I-V) curves in both resistance states. The QPC model has been found to be hard to apply, as the starting parameters have a strong influence on the fitting results. On the other hand, the SSA has proved its ability to provide good fits to the data and to do so better than other typical conduction mechanisms considered. However, its physical basis is criticized and it is concluded that in the devices studied, multiple subbands likely contribute to the conduction, in direct opposition to the assumptions made in such an approximation. A reinterpretation of the parameters of the SSA is proposed, to reconcile the increased performance with greater physical accuracy. Beyond that, the main challenges and difficulties regarding the application of the QPC to the case of valence-change-based ReRAM are discussed.