Role of atomic arrangements at interfaces on the phase control of epitaxial TiO2 films

Epitaxial rutile-TiO2 and anatase-TiO2 films were grown at 800 °C on Al2O3(1102) and LaAlO3(001), respectively, using pulsed laser deposition. Both films showed high crystalline quality, evidenced by x-ray diffraction and high-resolution electron microscopy. The formation of different phases on different substrates could be qualitatively explained by the atomic arrangements at the interfaces. We also deposited epitaxial rutile-TiO2 and anatase-TiO2 films on conductive RuO2 and La0.5Sr0.5CoO3 electrodes, respectively. Using a Kelvin probe, we measured the photovoltaic properties of these multilayer structures. A rutile-TiO2 film grown on RuO2 showed a very broad peak in the visible light region. An epitaxial anatase-TiO2 film grown on La0.5Sr0.5CoO3 showed a strong peak with a threshold energy of 3.05 eV.