Epitaxial stress study by large angle convergent beam electron diffraction and high-resolution transmission electron microscopy Moiré fringe pattern

Epitaxial stresses are studied by means of large angle convergent beam electron diffraction (LACBED) and Moiré fringe patterns obtained by high-resolution transmission electron microscopy in pulsed laser deposited thin films of Y–Ba–Cu–O on MgO substrate. Grains with their c-axis parallel to the interface grow from the substrate up to the outer surface of the film. These grains, embedded in the c-axis normal to the interface host matrix, are studied in cross-sectional samples, by both LACBED performed on the MgO substrate just beneath the different orientations of the thin film, and by the Moiré fringe patterns obtained by tilting the interface of the sample. The broadening of the Bragg lines present in the LACBED disk together with the direction of the Moiré fringes, clearly indicate that the c//-oriented grains embedded in a c⊥-oriented Y–Ba–Cu–O matrix are under stress.