Investigation of an 18 angstrom Al2O3 layer in a magnetic multilayer system by Rutherford and resonant scattering

Spin tunnel junctions, consisting of a metallic multilayer with a thin insu lating buffer layer, in most cases Al2O3, show a large tunneling magnetores istance (TMR) and are therefore of high interest for future magnetic read h eads and non-volatile memories. The properties of these junctions are stron gly influenced by the quality of the insulating buffer layer and its behavi or during thermal treatment. Measurements with conventional RES using devic es in the as-deposited state and after different heat treatments at tempera tures up to 200 degrees C revealed changes in the stoichiometry and O distr ibution in the buffer layer that can be correlated with changes in the resp ective magnetic properties. The application of the O-16(He-4, He-4)O-16 res onant scattering resonance with incident energies ranging from 3.01 to 3.35 MeV enabled the separate profiling of O in all parts of the sample: the pa rtly oxidized sample surface, the aluminum oxide layer and the silicon diox ide layer covering the Si substrate. Simulations of the energy dependence o f the O scattering yield showed that the oxygen is fully retained in the al uminum oxide buffer layer and no diffusion into adjacent metallic layers ha s occurred. The results indicate also that even Al2O3 layers with significa ntly lower thicknesses can be profiled with this method. (C) 2000 Published by Elsevier Science B.V. All rights reserved.