Transmission electron microscopy of La0.67Sr0.33MnO3/SrTiO3/La0.67Sr0.33MnO3 heterostructures grown by pulsed laser deposition on (001) SrTiO3

We have analysed by cross-section transmission electron microscopy (XTEM) La0.67Sr0.33MnO3/SrTO3/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 degrees); its epitaxy on SrTiO3 raises two binds 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. (C) 2000 Elsevier Science B.V. All rights reserved.