Visualization of structural domains in NdNiO₃/NdGaO₃ heterostructures

Ionic liquid gating is a versatile method for inducing phase transitions in a wide range of oxide materials, e.g., in the epitaxial NdNiO₃ films [1]. However, the microscopic mechanism of the induced phase transition, such as, the evolution of domain structures remains elusive and difficult to be probed under operando conditions. Here, we combine X-ray reflection interfacial microscopy (XRIM) and X-ray photon correlation spectroscopy (XPCS) to reveal the changes in the domain configuration and structures in NdNiO₃ films with TFSI-Dmim as the ionic liquid gating top layer. We compare the domain morphology of NdNiO₃ on different orientations of the NdGaO3 substrates both in the pristine state, during and after the ionic gating process. This comparison yields valuable information concerning the impact of substrate strain on the domain size, distribution and their mechanical rigidity upon repeating electric cycling. Our investigation sheds light on the pathway towards rational improvement and design for the ionic gating, and help accelerate the application of these devices in future microelectronics.