Interfacial and microstructural properties of $SrTiO3$ thin films grown on Si(001) substrates

The microstructure and interfaces of $SrTiO3$ thin films directly deposited by metalorganic chemical vapor deposition on silicon (001) substrates were investigated by means of Bragg-diffraction contrast and high-resolution transmission electron microscopy. The observation of the plan-view specimens showed that the $SrTiO3$ films are polycrystalline with randomly oriented grains. An amorphous layer was observed at the interfaces between the films and the substrates. The growth kinetics of this amorphous layer was investigated in detail. The thickness showed a rapid initial increase, which is much faster than the corresponding growth of amorphous $SiO2$ in the absence of precursors, and apparently approaches saturation after a short time. The thickness of the interfacial layer increases with the oxygen partial pressure during deposition and a reduction to a value acceptable for gate-oxide applications has been achieved for the minimum pressure given by the oxygen content of the present precursors. However, this comes at the cost of a dramatic increase of the carbon content of the film.