Synthesis of RuO2 Nanowires by Alkali-Assisted Oxidation of Ruthenium in Plasma Afterglow at Atmospheric Pressure

RuO 2 nanowires are synthesized by oxidation of ruthenium thanks to a micro-post-discharge at atmospheric pressure. However, RuO 2 nanowires form islands. The growth mechanism depending on surface defects, the surface density of the nanowires is limited. We report on the influence of two alkali salts, NaCl and KCl, deposited as grains on ruthenium to act as defects and increase the nanowire density. These grains induce the growth of RuO 2 nanowires all around them, creating a circular area where nanowires are found. Nanowires start growing at the triple point at the grain base where the alkali-salt grain, ruthenium from the substrate, and oxidizing gaseous species coexist. When nanowires grow, the stress induced in the surrounding layer creates new cracks, making possible the radial propagation of the nanowires. The presence of nanowires on grains is due to the etching mechanism that converts the alkali salt into an oxide, enabling onward oxidation of ruthenium.