Eur. Phys. J. Special Topics 167, 53-58 (2009)
DOI: 10.1140/epjst/e2009-00936-5

Crystalline structure of oxide-based epitaxial tunnel junctions

The effect of optical lithography studied by X-ray microdiffraction

C. Mocuta¹, A. Barbier², A.V. Ramos², M.-J.Guittet², J.-B. Moussy², S. Stanescu³, C. Gatel⁴, R. Mattana⁵, C. Deranlot⁵ and F. Petroff<sup>5

1</sup>  European Synchrotron Radiation Facility, BP. 220, 38043 Grenoble, France
²  CEA-Saclay, DSM/IRAMIS/SPCSI, 91191 Gif-sur-Yvette, France
³  Synchrotron SOLEIL, Saint-Aubin, BP. 48, 91192 Gif-sur-Yvette Cedex, France
⁴  Centre d'Élaboration des Matériaux et d'Études Structurales, CNRS, 31055 Toulouse, France
⁵  Unité Mixte de Physique CNRS/Thales, Route Départementale 128, 91767 Palaiseau Cedex and Université Paris-Sud 11, 91405 Orsay, France

mocuta@synchrotron-soleil.fr

Abstract
Epitaxial metal/oxide based magnetic tunnel-junctions (MTJ) are valuable model systems to investigate the influence of the crystallinity of individual layers on the magnetic properties. We have non-destructively studied the effect of the optical lithography procedure on the crystalline structure of MTJ's with lateral spatial resolution by performing local x-ray diffraction experiments using a microfocused x-ray spot. We demonstrate that the lithography process produces distortion effects on the crystalline structure of the layers near the edges of the lithographed junction. These distortions are present on all the constituent layers and are most probably driven by the elastic constants of the materials. They translate into tilts of the crystalline planes in the vicinity of the edges and propagate towards the center of the junction; the tilt's amplitude (up to several degrees) and sign (concave or convex) depend on the junction's shape, size and the type of materials (interfaces) used. We report results for junctions made with two types of metal-oxide interfaces ( and Co/Fe₃O₄), with sizes from 10 to 150 m and various shapes (square-, rectangle- and disk-like).

© EDP Sciences, Springer-Verlag 2009