Origin of The Time Relaxation of Volatile Valence Change Memory

Memristive devices based on the valence change mechanism are highly interesting candidates for data storage and hardware representation of synapses in neuromorphic circuits. Although long-term retention is often required for data storage applications, a time decay of the resistance is advantegous for several applications where short-term plasticity is required. In this work, we investigate in detail the LRS relaxation of volatile SrTiO₃ devices. The decay is analysed in terms of the Schottky-Read-Hall model for the contribution of electron traps and in terms of the Gibbs free energy gradient for the contribution of oxygen ion migration. Based on this, we can exclude trapping effects as origin oft he LRS decay. In contrast, we could nicely model the device behaviour by oxygen ion migration considering four reservoirs within the devices, connected by oxygen exchange. Our model serves as a tool for developing guidelines and design rules for future volatile memristive technology based on Schottky barrier mediated electron transport. As an example, we demonstrate the acceleration of the decay over 3 orders of magnetide by modifying the microstructure oft he SrTiO₃ layer.