Optoelectronic and Ionic Effects on Transport in van der Waals Metal Selenophosphate AgBiP2Se6

Ionic migration in solid phases is actively explored as a mechanism for neuromorphic computing elements, for example, but direct imaging of the ionic migration and its correlation with macroscopic electronic transport are tricky. Through multiple state-of-the-art microscopy techniques the authors visualize Ag${}^{+}$ migration in AgBiP${}_{2}$Se${}_{6}$, and how it modulates the interfacial barrier to induce switchable diodelike transport in a device. Illuminating the device can be used to switch off its ionic tunability, expanding its functionality. These results provide direct insight into the mechanism of ion-mediated transport in ionically active semiconductors.