Interface characterization of high-quality SrTiO₃ thin films on Si(100) substrates grown by molecular beam epitaxy

Single-crystal SrTiO₃ has been grown on Si(100) using molecular beam epitaxy (MBE). The growth conditions, especially at the initial stage of nucleation, have a great impact on the SrTiO₃/Si interface. A regrowth of an amorphous interfacial layer as thick as 23 angstroms has been observed and identified as a form of SiO_x. This is a direct result of an internal oxidation during the growth of the STO film due to the oxygen diffusion and reaction with the silicon substrate at the interface. The optimization of the deposition process in terms of growth temperature and oxygen partial pressure has led to an interfacial layer as thin as 11 angstroms. Metal oxide semiconductor (MOS) capacitors with an equivalent oxide thickness t_ox of 12 angstroms and a leakage current of 2×10^-4 A/cm² have been obtained for a 50 angstroms SrTiO₃.