Thin crystalline oxide films on silicon show a wide range of new electronic, optical, and magnetic properties with potential impact on novel devices. Precision control of the composition, stoichiometry and structure of such films and the ability to characterize the films and their interfaces are therefore of central importance.

We have used high-resolution medium energy (~ 100 keV) ion scattering (MEIS) to investigate the composition and structure as a function of depth of thin (40-250 Å) crystalline SrTiO₃ films on Si (100). As ion beams are penetrating, and the ion-solid interaction is well understood, this technique allows us to get quantitative information both about the film/vacuum and about the film/substrate interface structure. Different channeling and blocking geometries have been utilized to distinguish epitaxial/amorphous regions, to characterize the chemical composition of the SrTiO₃/Si interface and also to give information about structural parameters.

Thin SrTiO3 films were grown epitaxially on Si(001) at the low temperatures in an excess of oxygen. Our MEIS results show that films grown by this method have A-site (SrO) termination. We further show that submonolayer amounts of strontium silicide, used in the initial stages of growth, are fully eliminated from the interface after growth is completed and that instead Ti has diffused into the interface region. The SrTiO3/Si interface was confirmed to be crystalline; however the geometrical structure deviates significantly both from the 'bulk' epitaxial film and from the substrate.

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