Grain boundary engineering of 2D materials for nano-ionic Resistive Switches

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Resistive switches (RRAMs) are promising candidates for future non-volatile memories and logic-in-memory architectures. In these two-terminal devices, logic states are encoded by reversible manipulation of the device resistance upon short voltage pulses. The resistance transition is attributed to the growth and rupture of a nanoscale conductive filament driven by the migration of mobile oxygen vacancies or metal cations, such as silver or copper ions depending on the materials used. In the latter case ultra-low switching energies below 10 fJ/bit are predicted. Despite their advantages including, scalability and compatibility with cost-saving standard back-end-of-line fabrication processes, the inferior device stability due to uncontrolled metal particle diffusion impedes their practical application. Graphene has been recently suggested as ultra-thin two-dimensional diffusion barrier. However, the ion diffusion through 2D materials integrated in RRAMs is unexplored which hinders device optimisation. We propose to integrated two-dimensional hexagonal boron nitride (hBN) in vertical and lateral resistive switches. In particular, we will characterize the switching behaviour in presence of grain boundaries and analyze how these can be exploited and tuned to improve the switching performance. Electrical measurements will be complemented by a recently introduced technique, so called plasmon-enhanced spectroscopy, to probe morphological changes upon resistive switching. As the ambient atmosphere is significantly involved during the switching, switching mechanisms will be further analyzed using in situ environmental microscopic and spectroscopic techniques. This project will bring a step change in the understanding of these devices, which is needed to unlock their full application potential.