Asymmetric rocking curve study of the crystal structure orientations for BaTiO3 thin films grown by pulsed laser deposition

We have investigated systematically the oxygen pressure dependences of the crystalline phases and the crystallographic orientations of BaTiO3 thin films by means of asymmetric rocking curves. Epitaxial BaTiO3 thin films were grown on SrTiO3 (001) substrates by pulsed laser deposition (PLD) under different oxygen pressures. The X-ray diffraction θ/2θ scans showed no diffraction peaks from impurity phases or randomly oriented grains, indicating that the thin films were single phase BaTiO3. The XRD ω rocking curves indicated that the BaTiO3 thin films had a very high degree of crystallinity. The XRD φ scans showed that no in-plane misorientation existed in the BaTiO3 thin films. The results of asymmetric rocking curves showed that the BaTiO3 thin films grown under higher oxygen pressures(>12 Pa) were tetragonal with a-axis orientation, those grown under lower oxygen pressures (<7 Pa) were tetragonal with c-axis orientation, and those grown under intermediate oxygen pressures (∼7–12 Pa) were cubic.