Substrate influence on the shape of domains in epitaxial PbTiO3 thin films

Epitaxial PbTiO3 thin films were grown on SrTiO3(001) and DyScO3(110) substrates by pulsed laser deposition. We used high-resolution transmission electron microscopy to investigate the 90 degrees domain structure in the films. They were found to have a predominant fraction of c domains along with a certain minor volume fraction of a domains that is clearly higher in case of the DyScO3 substrates. In PbTiO3 on SrTiO3 the a domains were found to have a wedge shape, whereas in PbTiO3 on SrRuO3/DyScO3 they have a nearly uniform width. The presence of steps in the domain walls has been observed in the films on both substrates, but the steps are clearly more dominant in the case of SrTiO3 than of SrRuO3/DyScO3 and are responsible for the observed wedge shape. The observed difference in the films induced by the two substrates is attributed to a higher stiffness of SrTiO3 than of SrRuO3/DyScO3 as we corroborated with nanoindentation experiments. (c) 2007 American Institute of Physics.