The growth stress of titanium films was measured in situ with a cantilever beam technique under UHV conditions at Ts ≥ 130°C. The substrate used in these experiments was a double layer consisting of a base layer of A12O3 or of MgF2 and as a second layer a titanium film evaporated at different H2O-partiaI pressures (Ti/TiOx). With both base layers the growth stress of the substrate Ti/TiOx layer is similar.

The main objective of this paper was the investigation of the effect of a variation in the chemical composition of the substrate Ti/TiOx layer on the growth stress and -by way of our stress model - on the growth mode of a clean titanium film always evaporated under identical vacuum conditions onto this bilayered substrate. At low water content of the substrate titanium layer (the substrate layer still consists of metallic titanium) the growth of the clean titanium film is a continuation of the growth of the second substrate layer. As soon as the substrate titanium film contains only a few percent of water the initial compressive stress is overcompensated by atensile stress contribution which increases as the water content of the substrate isincreased. We interprete this to indicate renewed nucleation for the clean titanium film on the substrate surface. A small part of the tensile stress is also due to gas interdiffusion (hydrogen) from the substrate film. This effect is rather small when the second substrate film consists of stoichiometric oxide. With a MgF2 base layer in the substrate bilayer the results indicate a diffusing species from the MgF2 base layer into the Ti/TiOx layer. This interdiffusion from the substrate significantly affects the growth stress of the clean titanium film on this substrate bilayer. However, the general trends due to the incorporation of water in the substrate Ti/TiOx film, seen in case of the A12O3 base layer, are the same.