TEM and EELS measurements of interface roughness in epitaxial Fe/MgO/Fe magnetic tunnel junctions

Received 3 December 2007; revised manuscript received 31 March 2008; published 13 April 2009The crystalline structure, chemical composition, and bonding states across epitaxial Fe/MgO/Fe 001 mag-netic tunnel junctions grown by molecular-beam epitaxy have been investigated down to the atomic scale byspatially resolved electron energy-loss spectroscopy. Both metal-insulator interfaces exhibit significant rough-ness, which can be attributed to Fe and MgO terraces overlapping one another. These terraces extend overtypical widths of 6–10 nm parallel to the interface and over typical heights below 1 nm, and a structuralasymmetry of the roughness is revealed. These features could be responsible for the nonsymmetrical transportproperties measured when reversing the applied voltage.DOI: 10.1103/PhysRevB.79.144413 PACS number s : 79.20.Uv, 68.37.Lp, 85.75. d, 73.40.Rw

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