Molecular Beam Epitaxy of SrTiO₃ Films on Si(100)-2×1 with SrO Buffer Layer

Abstract

Molecular beam epitaxy of SrTiO 3 thin films on a Si(100)-2×1 surface has been studied using reflection high-energy electron diffraction (RHEED), an atomic force microscope (AFM) and X-ray diffraction (XRD) as a function of the thickness of the SrO buffer layer and growth temperature. Epitaxial SrTiO 3 films do not grow directly on Si(100). Therefore, a SrO buffer layer was applied to grow SrTiO 3 on Si(100). It was found that the SrO layer with a thickness of 100 Å grown at 300 – 400°C in oxygen atmosphere of 5 ×10 -8 Torr was sufficient to grow epitaxial SrTiO 3 on Si(100). Then SrTiO 3 thin films with a thickness of 2000 Å were grown on the SrO(100Å)/Si surface at 400 – 700°C using codeposition of strontium and titanium in oxygen atmosphere of 8×10 -8 Torr. At 500°C, the best-quality SrTiO 3 (100) film grew parallel to Si(100), and numerous rectangular platelike crystals were observed on the surface in the AFM image. The crystallinity of the STO films was improved with increasing thickness of the SrO layer. The epitaxial relation between SrTiO 3 and SrO/Si(100)-2×1 is also discussed using the RHEED patterns which show streaks and spots.