Growth of SrTiO₃ on Si(001) by hybrid molecular beam epitaxy

We report the heteroepitaxial growth of SrTiO₃ thin films on Si(001) by hybrid molecular beam epitaxy (hMBE). Here, elemental strontium and the metal-organic precursor titanium tetraisopropoxide (TTIP) were co-supplied in the absence of additional oxygen. The carbonization of pristine Si surfaces during native oxide removal was avoided by freshly evaporating Sr into the hMBE reactor prior to loading samples. Nucleation, growth and crystallization behavior as well a structural properties and film surfaces were characterized for a series of 46-nm-thick SrTiO₃ films grown with varying Sr to TTIP fluxes to study the effect of non-stoichiometric growth conditions on film lattice parameter and surface morphology. High quality SrTiO₃ thin films with epitaxial relationship (001)SrTiO₃ || (001)Si and [110]SrTiO₃ || [100]Si were demonstrated with an amorphous layer of around 4 nm thickness formed at the SrTiO₃/Si interface. The successful growth of high quality SrTiO₃ thin films with atomically smooth surfaces using a thin film technique with scalable growth rates provides a promising route towards heterogeneous integration of functional oxides on Si. The authors report the successful heteroepitaxial growth of high quality SrTiO₃ thin films on Si with atomically smooth surfaces and controllable stoichiometry using a combinatorial thin film growth technique. The inherent ability to scale up the growth rates provides a promising route towards heterogeneous integration of functional oxides on Si.