Epitaxial c -axis oriented BaTiO₃ thin films on SrTiO ₃-buffered Si(001) by atomic layer deposition

Abstract

Atomic layer deposition (ALD) of epitaxial c-axis oriented BaTiO 3 (BTO) on Si(001) using a thin (1.6 nm) buffer layer of SrTiO 3 (STO) grown by molecular beam epitaxy is reported. The ALD growth of crystalline BTO films at 225 C used barium bis(triisopropylcyclopentadienyl), titanium tetraisopropoxide, and water as co-reactants. X-ray diffraction (XRD) reveals a high degree of crystallinity and c-axis orientation of as-deposited BTO films. Crystallinity is improved after vacuum annealing at 600 C. Two-dimensional XRD confirms the tetragonal structure and orientation of 7-20-nm thick films. The effect of the annealing process on the BTO structure is discussed. A clean STO/Si interface is found using in-situ X-ray photoelectron spectroscopy and confirmed by cross-sectional scanning transmission electron microscopy. The capacitance-voltage characteristics of 7-20 nm-thick BTO films are examined and show an effective dielectric constant of ∼660 for the heterostructure. © 2014 AIP Publishing LLC.