Influence of active electrode impurity on memristive characteristics of ECM devices

Memristive devices are promising candidates for the implementation in more than Moore applications. Their functionalities, electrical characteristics, and behavior, such as high scalability and stability at extreme conditions such as low/high temperatures, irradiation with electromagnetic waves and high-energy particles, and fast operation are required for solving current problems in neuromorphic architectures. Electrochemical metallization (ECM)-based memristive devices are among the most relevant in this scenario owing to their low power consumption, high switching speed, showing high HRS/LRS resistance ratio in digital mode, and as well multilevel to analogue-type performance, allowing to be used in wide spectrum of applications, including as artificial neurons and/or synapses in brain-inspired hardware. Despite all the advantages and progressing industrial implementation, effects of materials selection and interactions are not sufficiently explored, and reliable design rules based on materials approach are still to be formulated by the correct choice of structures and materials combinations to ensure desired performance. In this work, we report on the effects of impurities in the copper active electrode on the electrical characteristics of Cu/Ta2O5/Pt ECM devices. The results demonstrate that Cu impurity is modulating the electrochemical behavior and switching speed due to different catalytic activity and redox reaction rates. In addition, stability and variability are improved by decreasing the number of foreign atoms. Our results provide important additional information on the factors needed to be considered for rational device design.