Effect of the electrode layer on the polydomain structure of epitaxial PbZr0.2Ti0.8O3 thin films

PbZr0.2Ti0.8O3(PZT) thin films with and without La0.5Sr0.5CoO3(LSCO) electr odes were grown epitaxially on (001) SrTiO3 at 650 degrees C by pulsed lase r deposition. The domain structure of the 400 nm thick PZT films with diffe rent electrode layer configurations was investigated by x-ray diffraction a nd transmission electron microscopy. The c-domain fractions of the PZT film s with no electrode layer, with a 50 nm electrode layer between the film an d the substrate, and with 50 nm electrode layers on top and bottom of the P ZT film were found to be equal. Theoretical estimation of the c-domain frac tion based on the minimization of the energy of internal stresses in films is in good agreement with experimental results. This means that depolarizin g fields do not affect the polydomain structure of the film. Calculations o f the in-plane strains based on the lattice parameters of the LSCO layer in the above configurations led to the conclusion that the bottom electrode l ayer is coherently strained to match the substrate. (C) 1999 American Insti tute of Physics.