Characteristic length scales of the electrically induced insulator-to-metal transition

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.

Automated summary

Some correlated materials exhibit an insulator-to-metal transition with increasing temperature, which can also be induced electrically. This transition results in volatile resistive switching due to the formation of conducting filaments. Despite attracting significant attention, there remain unresolved fundamental questions, including the characteristic lengths of these filaments and their impact on switching properties. Through the use of wide-field and scattering-type scanning near-field optical microscopies, filament formation in NdNiO3 and SmNiO3 thin films are characterized. It is observed that smaller filaments increase current density, leading to sharper switching and larger resistive drops. Numerical simulations are employed to discuss the parameters governing filament width and switching properties.