Stress Levels In Films Research Articles

Multiple relaxation mechanisms in SrTiO3/SrRuO3 heterostructures

We have studied stress relaxation mechanisms in epitaxial (001) SrTiO3 films grown on (001) LaAlO3 substrates with SrRuO3 buffer layers. A theoretical analysis has been undertaken to understand the variation of the lattice parameters of SrTiO3 epitaxial films, taking into account stress relaxation due to the formation of an orthorhombic polydomain structure in the SrRuO3 buffer layer as well as the formation of misfit dislocations at the LaAlO3/SrRuO3 and the SrTiO3/SrRuO3 interfaces. There exists a critical SrRuO3 buffer layer thickness, above which the SrRuO3 buffer layer can “screen” the effect of the LaAlO3 substrate. It is shown that the internal stress level in films can be controlled using buffer layers that exhibit a structural phase transformation.

The effect of substrate temperature on the magnetic and structural properties of Ni-Fe thin films deposited in ultrahigh and ordinary vacuum

An investigation was undertaken of the effects of substrate temperature on the magnetic and structural properties of 80.5wt.%Ni-19.5wt.%Fe films deposited in ultrahigh vacuum. The results showed that the variation in Hoffmann's structure constant S with substrate temperature is dependent on the deposition conditions, the variation being much larger for films prepared in ordinary vacuum than for those prepared in ultrahigh vacuum. This was attributed to differences in the stress levels in films prepared in the two types of vacuum environment. The large values of stress in films deposited at ambient temperature and the reduction in stress with increasing substrate temperature (both of which are observed only in films deposited in ordinary vacuum) are interpreted as being due to the incorporation in the films of oxygen impurity atoms and to a grain boundary phenomenon.