Strain relaxation in sol-gel grown epitaxial anatase thin films

Anatase TiO₂ thin films on LaAlO₃ (LAO) substrates were epitaxially grown at a temperature as low as 350 °C using a simple sol-gel process. X-ray diffraction and high-resolution transmission electron microscopy showed that the anatase films have the epitaxial relationship of (001)TiO₂∥(001)LaAlO₃. While the low-temperature growth of the anatase film yielded a residual strain, subsequent annealing at higher temperatures can remove the strain and recover the lattice parameters of a perfect anatase crystal. Measurements of the oxygen content in the anatase films by non-Rutherford elastic resonance scattering analysis suggest that the strain relaxation during higher temperature annealing is due to the incorporation of oxygen and the concomitant annihilation of oxygen vacancies.