Stress relaxation in c perpendicularto -c// YBaCuO thin films on MgO substrate studied by LACBED

Thin films of YBaCuO grown by in situ pulsed laser deposition on MgO substrate are studied by means of high resolution transmission electron microscopy imaging and large angle convergent beam electron diffraction experiments. Both c// and c perpendicularto YBaCuO crystals coexist in the film. The diffraction experiments are performed on the MgO substrate along the interface with the YBaCuO film. Some of the Bragg lines exhibit a dramatic broadening when the electron probe is just below the c// oriented crystal. This result is interpreted in terms of lattice strain relaxation due to the thinning of the TEM sample. This relaxation phenomenon indicates that the c// oriented grains embedded in a c perpendicularto oriented host matrix of YBaCuO, are under stress. (orig.)