Integration of BaTiO 3 on Si (0 0 1) using MgO/STO buffer layers by molecular beam epitaxy

Abstract

The integration of epitaxial BaTiO 3 (BTO) on (0 0 1) oriented silicon using MgO as a buffer layer was investigated. An SrTiO 3 (STO) thin film was used as an intermediate buffer layer to reduce strain between the MgO and Si. The STO thin films were deposited by molecular beam epitaxy (MBE) with solid elemental metal sources and molecular oxygen as the oxidant. The MgO/STO double layer stack serves as an excellent platform for epitaxial growth of thick BTO thin films on Si (0 0 1) by metalorganic chemical vapor deposition (MOCVD). Epitaxial quality, microstructure and surface morphology of the fully integrated stack were studied by in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), atomic force microscopy (AFM), and cross sectional transmission electron microscopy (XTEM). The analyses indicate that the integrated BTO and underlying MgO/STO buffer layers have an orientational relation given by BTO (0 0 1) ||MgO (0 0 2) ||Si (0 0 4) and BTO〈1 0 0〉 ||MgO〈2 0 0〉 ||Si〈1 1 0〉. The full width at half maximum (FWHM) of MgO (0 0 2) and BTO (0 0 2) rocking curves or Δ ω=1.1° and 1.3°, and FWHMs of MgO (2 0 2) and BTO (2 0 2) phi scan peaks or Δ φ=1.3° and 1.6°, respectively, are achieved. The measured values Δ ω and Δ φ are comparable to those reported for BTO on single crystal MgO substrate. The interfaces between the layers are abrupt.