When Memristance Crosses the Path with Humidity Sensing-About the Importance of Protons and Its Opportunities in Valence Change Memristors

Resistive switching devices based on oxides have outstanding properties, making them a promising candidate to replace today's transistor-based computer memories as non-volatile valence change memories, and can even find future application in neuromorphic computing. To date, the scientific discussion is so far mainly restricted to oxygen vacancy contributions disregarding the role of protonic defects on resistive switching. In this work, the effect of moisture and protonic contributions on resistive switching by changes in the surface to bulk ratio and oxide surface exposure of the oxide SrTiO3 is studied. Here, a linear to exponential SET current density dependency, when changing the film thickness by a factor of four, is found, whereby the surface-to-bulk ratio of the oxide is significantly changed. This behavior is discussed in terms of differences in total concentration of oxygen vacancies and their interplay with moisture. For classic memristor applications, this study demonstrates that protonic defects need to be accounted for memristor characteristics, as they crucially influence the switching characteristics, and give new opportunities as an additional handle to actively tune the switching performance. This memristive dependency on protonic defects opens a whole plethora of new modulatable sensor characteristics like creating humidity sensors using the property of memristance.