Transmission electron microscopy of La0.67Sr0.33MnO3/SrTiO3/ La0.67Sr0.33MnO3 heterostructures grown by pulsed laser deposition on (0 0 1) SrTiO3

We have analysed by cross-section transmission electron microscopy (XTEM) La0.67Sr0.33MnO3/ SrTiO3/La0.67Sr0.33MnO3 tunnel junctions epitaxially grown on (0 0 1) SrTiO3 by pulsed laser deposition (PLD). La0.67Sr0.33MnO3 (LSMO) is rhombohedral in bulk (pseudo-cubic with an angle of 89.76 deg. ); its epitaxy on SrTiO3 raises two kinds of questions: (1) are the interfaces chemically abrupt? And (2) is the LSMO strained to a tetragonal phase that would fit the cubic substrate? In the present paper, we show, using high-resolution TEM (HRTEM) micrographs and a semi-quantitative technique based on Chemical Mapping (A. Ourmazd et al., ultramicroscopy 34 (1990) 237) that the extent of roughness or interdiffusion at the interfaces is less than a single unit cell. On the other hand, we deduce from electron diffraction that the LSMO films are at least partially relaxed