Investigation of the MgO absorbate and the MgO/Fe on GaAs(001) surface by means of XPS and XPD

D. Handschak, F. Schönbohm, T. Lühr, C. Keutner, U. Berges, C. Westphal
TU Dortmund, DE

Keywords: XPS, XPD, thin film adsorbtion

Summary:

We report a combined high-resolution photoemission and photoelectron diraction investigation of a magnesium oxide adsorbate on an Fe surface grown on a GaAs(4x2)-reconstructed substrate. MgO is an appliciable insulator in magnetic tunnel junctions (MTJ) based on tunnel magnetoresistance. TMR-components are also of interest in the research of magnetoresistive random access memories. In this study we report on the crystalline properties of the MgO adsorbate and on the MgO/Fe interface. The results of the diraction patterns revealed an interface with oxidized iron layers and partially shifted magnesium layers in a halite structure. The high resolution XPS core level spectra of the Mg 2p and Fe 3p prove a successful preparation of the topmost Mg layers. The analysis of the XPD patterns yielded in an interface structure consisting of two iron oxides layers located on an iron bcc elementary cell. The MgO layers are of halite structure with a rotation of 45 with respect to the Fe bcc surface. The best agreement was achieved for a model where every second Mg layer is shifted slightly with respect to the other ones. This structure model is supported by the superposition of the individual simulated diraction pattern of Mg 2p and Fe 3p signals.