Oxidation of RuAl and NiAl Thin Films: Evolution of Surface Morphology and Electrical Resistance

Abstract

RuAl and NiAl thin films on SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /Si were oxidized, and the results were compared to those from aluminum, ruthenium, and nickel films. Both aluminides are more oxidation resistant than nickel, aluminum, and ruthenium, and they form an outer layer of alumina after oxidation to 850 °C. The depth profiles differ for NiAl and RuAl, with alternating layers of alumina and a Ru-rich phase forming on RuAl, while a more complex structure forms on NiAl due to reaction with the substrate. The surface of RuAl after oxidation remains fairly smooth and reflective, whereas NiAl has a hazy appearance. However, the surface morphology changes at a slightly lower temperature in the case of RuAl (~ 500°C) . Both films remain conductive even after the surface begins to show signs of oxidation, with the NiAl remaining conductive to a higher temperature (after 1 h at 850 °C) than RuAl. The results show that NiAl and RuAl films can be used in an oxidizing atmosphere up to ~ 500°C (at least 1 h) for applications requiring a smooth reflective surface and to higher temperatures when the surface quality is less important but conductivity needs to be maintained (~ 800°C for RuAl and ~ 850°C for NiAl).