  Integration of functional oxides on silicon requires the use of complex
heterostructures involving oxides of which the structure and properties
strongly depend on the strain state and strain-mediated interface coupling. The
experimental observation of strain-related effects of the individual components
remains challenging. Here we report a Raman scattering investigation of complex
multilayer BaTiO3/LaNiO3/CeO2/YSZ thin film structures on silicon. It is shown
that the Raman signature of the multilayers differs significantly for three
different laser wavelengths (633, 442 and 325 nm). Our results demonstrate that
Raman scattering at various wavelengths allows both the identification of the
individual layers of a functional oxide multilayers and monitoring their strain
state. It is shown that all layers of the investigated multilayer are strained
with respect to the bulk reference samples, and that strain induces a new
crystal structure in the embedded LaNiO3. Based on this, we demonstrate that
Raman scattering at various wavelengths offers a well-adapted, non-destructive
probe for the investigation of strain and structure changes, even in complex
thin film heterostructures.
