Ferroelectric Phase Transition in BaTiO3Films

Films of BaTiO 3 single crystals with the thicknesses of 100 Å, 1000 Å and 4000 Å were grown on Pt/MgO (Pt for electric nodes, MgO for substrates) by means of the activated reactive evaporation technique. X-ray diffraction patterns were measured to clarify properties such as the temperature dependence of lattice parameters. It was found that the temperature dependences of lattice parameters and integrated intensities of Bragg reflections showed different behavior which depends on the film thickness. The relative dielectric constant ε r and remnant polarization P r were measured in order to investigate the dielectric properties of the films. Film crystals of BaTiO 3 with the thickness of 4000 Å showed phase transitions different from these in the bulk state because of the effect of the substrate.