Activation energy distribution of dynamical structural defects in RuO$_2$ films

TL;DR

This study investigates the origin of 1/f noise in RuO₂ films, attributing it to fluctuating oxygen vacancies, and quantifies the activation energy distribution and vacancy density to improve understanding of defect dynamics.

Contribution

It provides a novel quantitative analysis of the activation energy distribution of oxygen vacancies in RuO₂ films and links it to noise characteristics and defect densities.

Findings

Reducing oxygen vacancies decreases noise magnitude.

The activation energy distribution g(E) is explicitly derived.

Oxygen vacancy density aligns with x-ray photoelectron spectroscopy data.

Abstract

Ruthenium dioxide (RuO$_2$) is an important metal widely used in nanoelectronic devices. It plays indispensable roles in the applications as catalyst and supercapacitors. A good understanding of the origin of the flicker or 1/$f$ noise in RuO$_2$ will advance the design and efficiency of these applications. We demonstrate in a series of sputtered RuO$_2$ polycrystalline films that the 1/$f$ noise originates from fluctuating oxygen vacancies which act as dynamical structural defects, i.e., moving scattering centers. Reducing the number of oxygen vacancies by adjusting thermal annealing conditions significantly reduces the noise magnitude $\gamma$, the Hooge parameter. We quantify the activation energy distribution function, $g(E)$, and calculate the oxygen vacancy density, $n_{TLS}$, from the measured $\gamma$ value. We show that $g(E)$ can be explicitly expressed in terms of $\gamma(T)$ and the electronic parameters of the metal, where $T$ denotes temperature. The inferred $n_{TLS}$ value is in line with the oxygen content determined from the x-ray photoelectron spectroscopy studies.