Characteristic lengthscales of the electrically-induced insulator-to-metal transition

TL;DR

This paper investigates the characteristic lengthscales of electrically-induced insulator-to-metal filaments in correlated materials, revealing how filament size influences switching sharpness and resistive change through microscopy and simulations.

Contribution

It provides the first detailed characterization of filament lengthscales in NdNiO3 and SmNiO3, linking filament size to switching behavior and offering insights into controlling resistive switching.

Findings

Smaller filaments lead to higher current density.

Filament size correlates with sharper switching.

Numerical simulations identify parameters influencing filament width.

Abstract

Some correlated materials display an insulator-to-metal transition as the temperature is increased. In most cases this transition can also be induced electrically, resulting in volatile resistive switching due to the formation of a conducting filament. While this phenomenon has attracted much attention due to potential applications, many fundamental questions remain unaddressed. One of them is its characteristic lengths: what sets the size of these filaments, and how does this impact resistive switching properties. Here we use a combination of wide-field and scattering-type scanning near-field optical microscopies to characterize filament formation in NdNiO3 and SmNiO3 thin films. We find a clear trend: smaller filaments increase the current density, yielding sharper switching and a larger resistive drop. With the aid of numerical simulations, we discuss the parameters controlling the filament width and, hence, the switching properties.