Improving the oxidation resistance of RuAl thin films with Al2O3 or SiO2 cover layers

A sufficient oxidation resistance of RuAl thin films is crucial for their application in high temperature sensors e.g. based on the surface acoustic waves principle. To improve the high temperature stability, an Al2O3 or SiO2 cover layer is added to protect the films from oxidation especially for application in air. The covered RuAl films are annealed at temperatures up to 900 °C under high vacuum and in air for 10 h. X-ray diffraction, cross section imaging and Auger electron spectroscopy are applied to reveal the suitability of the cover layers as oxidation barrier. While there is hardly any difference between the samples with or without cover layer after annealing under high vacuum, only the samples with SiO2 cover are stable up to 800 °C in air. [Display omitted] •110 nm thick RuAl films with a 20 nm Al2O3 or SiO2 cover layer are prepared.•The films are annealed up to 900 °C under high vacuum and in air for 10 h.•A cover layer hardly influences the film properties after annealing under HV.•The Al2O3 cover layer fails during annealing at 800 °C in air.•The SiO2 cover layer realizes a clearly improved stability up to 800 °C in air.