Oxidation of Ruthenium

Ruthenium (Ru) has been heated in air in the range of 100-400°C in order to investigate its usefulness for electrical contacts. It has been found that for temperatures up to 200°C, Ru oxidizes to produce a film which causes high contact resistance. For temperatures >300°C, Ru forms an oxide film, RuO
2
, which has low contact resistance. Electron spectroscopy for chemical analysis (ESCA) reveals that the oxide which forms at temperatures <200°C is a lower oxide of Ru (probably RuO) and is chemically different than the oxide film formed at high temperatures (>300°C). More work is required to define precisely the temperature above which RuO
2
is the predominant species. Ru contacts in actual applications will be subjected to temperatures <100°C. This may make Ru an inappropriate contact material.