Interface structure and thermal stability of epitaxial SrTiO₃ thin films on Si (001)

We have used medium energy ion scattering, temperature programmed desorption, and atomic force microscopy to study the interface composition and thermal stability of epitaxial strontium titanate thin films grown by molecular-beam epitaxy on Si (001). The composition of the interface between the film and the substrate was found to be very sensitive to the recrystallization temperature used during growth, varying from a strontium silicate phase when the recrystallization temperature is low to a Ti-rich phase for a higher recrystallization temperature. The films are stable towards annealing in vacuum up to ∼550 °C, where SrO desorption begins and the initially flat film starts to roughen. Significant film disintegration occurs at 850 °C, and is accompanied by SiO and SrO desorption, pinhole formation, and finally titanium diffusion into the silicon bulk.