Synthesis of RuO2 nanowires from Ru thin films by atmospheric pressure micro-post-discharge

Oxidation by a micro-post-discharge at atmospheric pressure of thin films of ruthenium deposited on fused silica by pressure-modulated magnetron sputtering is studied. Single-crystalline RuO2 nanowires are obtained for the first time with a diffusion process over large areas. Nanowires grow typically at temperatures below 550-600 K, provided the level of stress is high enough to fragment grains in sub-grains with sizes between 30 and 50 nm. Because of the alternation of dense and porous layers forming the coating, inward diffusion of vacancies leads to no patent Kirkendall's effect, pores being distributed over the whole coating thickness and not mainly at the interface with the substrate. The centre of the treatment being heated at temperatures higher than 900 K, gaseous RuO4 is formed, leading to an evaporated area. At its edge, a ring of microcrystals is formed, likely by a CVD mechanism.