Growth and characterization of epitaxial anatase TiO2(001) on SrTiO3-buffered Si(001) using atomic layer deposition

Epitaxial anatase titanium dioxide (TiO2) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO2 was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225–250 °C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600 °C in vacuum (10− 7 Pa) for 1–2 h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO2 by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO2 growth. X-ray diffraction revealed that the TiO2 films were anatase with only the (004) reflection present at 2θ = 38.2°, indicating that the c-axis is slightly reduced from that of anatase powder (2θ = 37.9°). Anatase TiO2 films up to 100 nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates.

► Epitaxial anatase films are grown by atomic layer deposition (ALD) on Si(001).
► Four unit cells of SrTiO3 on silicon create a stable template for ALD.
► TiO2 thin films have a compressed c-axis and an expanded a-axis.
► Up to 100 nm thick TiO2 films remain highly ordered in the (001) direction.