The influence of barrier layers (SiO2, Al2O3, W) on the phase formation and stability of RuAl thin films on LGS and CTGS substrates for surface acoustic wave technology

Abstract In order to achieve a higher thermal stability of RuAl thin films on LGS (La 3 Ga 5 SiO 14 ) and CTGS (Ca 3 TaGa 3 Si 2 O 14 ) substrates and to prevent an oxidation with Oxygen originating from the substrates various barrier layers (SiO 2 , Al 2 O 3 , W) are tested. The RuAl-barrier films were annealed at 800 °C for 10 h under high vacuum conditions. An analysis of the phase formation as well as of changes in the chemical composition of the RuAl film and the substrate reveals a strong dependence of the quality of the RuAl film on the applied barrier layer. In the case of Al 2 O 3 a reaction between RuAl and the substrates takes place. The application of W films is challenging because of the high stresses which are present in the layer stack. However, SiO 2 films act successfully as diffusion barriers.