Proton distribution visualization in perovskite nickelate devices utilizing nanofocused X-rays

TL;DR

This study employs nanofocused X-ray techniques to spatially resolve how proton doping affects the electronic properties of SmNiO3 devices, revealing valence changes without significant lattice distortion.

Contribution

It demonstrates that proton doping primarily alters electronic valency rather than crystal structure in SmNiO3, using high-resolution X-ray methods supported by DFT simulations.

Findings

Proton doping reduces nickel valence in specific regions.

Minimal lattice distortion observed despite doping.

Electronic changes dominate over structural effects.

Abstract

We use a 30-nm x-ray beam to study the spatially resolved properties of a SmNiO$_3$-based nanodevice that is doped with protons. The x-ray absorption spectra supported by density-functional theory (DFT) simulations show partial reduction of nickel valence in the region with high proton concentration, which leads to the insulating behavior. Concurrently, x-ray diffraction reveals only a small lattice distortion in the doped regions. Together, our results directly show that the knob which proton doping modifies is the electronic valency, and not the crystal lattice. The studies are relevant to on-going efforts to disentangle structural and electronic effects across metal-insulator phase transitions in correlated oxides.