Hydrogenated Rare-Earth Nickelate Nanojunctions with Synaptic Behavior Studied by X-ray Nanodiffraction*

Rare-earth nickelates have been the target of intense fundamental and application-focused studies due to their rich phase diagram and possible utilization of these materials as novel sensors, memory devices and hardware elements for artificial intelligence. For example, hydrogenation of SmNiO₃ (SNO) drastically changes its electronical properties giving rise to a new insulating phase. Moreover, application of voltage pulses allows one to repeatedly switch the hydrogenated SNO films between the lower and higher resistance states. This allows one to create a device with synaptic behavior, which is a crucial hardware element for neuromorphic computing. With nanofocused x-ray diffraction and spectroscopy we performed in-situ spatially-resolved studies of the microscopic mechanism behind the potentiation and depression of an SNO-based device. We revealed changes in both electronic structure and crystal lattice between pristine and hydrogenated SNO films, as well as before and after electrical switch of the device.