2... 100 nm thin Cu or Al layers were prepared either separately or consecutively at 100 degrees C using the physical vapour deposition technique. Glass slides were used as substrate. The surface tension of the metal layers degrees(s) was characterized. The surface tension of the Al-layers was 70 +/- 1 mN/m. For the Cu-layers, a surface tension of 57 +/- 2 mN/m was determined. In the case of a consecutive glass-Al-Cu system, the surface tension is identical with a pure Al-layer. The surface tension of consecutive glass-Cu-Al layers was 2...3 mN/m lower than for pure Al-layers. These differences result from the different diffusion behaviours of both metals. XPS investigations show that Al atoms can penetrate into the Cu bulk up to 20 nm. In contrast, the penetration of Cu atoms into the Al bulk was not observed.