The Influence of the Composition of Ru(100−x)Al(x) (x = 50, 55, 60, 67) Thin Films on Their Thermal Stability

RuAl thin films possess a high potential as a high temperature stable metallization for surface acoustic wave devices. During the annealing process of the Ru-Al films, Al [Formula: see text] O [Formula: see text] is formed at the surface of the films even under high vacuum conditions, so that the composition of a deposited Ru [Formula: see text] Al [Formula: see text] film is shifted to a Ru-rich alloy. To compensate for this effect, the Al content is systematically increased during the deposition of the Ru-Al films. Three Al-rich alloys—Ru [Formula: see text] Al [Formula: see text] , Ru [Formula: see text] Al [Formula: see text] and Ru [Formula: see text] Al [Formula: see text] —were analyzed concerning their behavior after high temperature treatment under high vacuum and air conditions in comparison to the initial Ru [Formula: see text] Al [Formula: see text] sample. Although the films’ cross sections show a more homogeneous structure in the case of the Al-rich films, the RuAl phase formation is reduced with increasing Al content.