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Longitudinal-XRD scan from a 25 nm thick FePt layer grown under identical conditions as p-MTJs. (inset) FePt(002) reflection from a FePt(25 nm)/MgO(3 nm)/FePt(50 nm) sample, in which the doublet indicates that the top FePt layer is under higher tensile strain than the bottom layer.
(a) Cross-sectional HRTEM image of the entire p-MTJ structure obtained along the MgO[1-10] direction. Power-spectra from regions denoted schematically by the red squares in (b) top FePt electrode, (c) MgO barrier, and (d) bottom FePt electrode. These power spectra show the L10-FePt(001)//MgO(001)//L10-FePt(001) epitaxial relation and confirm the L10 structure of FePt electrodes. (e) HRTEM cross-sectional image of the FePt electrodes and MgO barrier. Inset (top right): power-spectrum from a region including the bottom electrode and barrier shows splitting of the (220) reflection, marked schematically by the red circle. Inset (center): reconstructed image of the semi-coherent interface between the bottom FePt electrode and MgO barrier using the (220) reflection in which misfit dislocations are marked schematically by the red arrow.
(a) HAADF-STEM (inner detector semi-angle: 78 mrad) image demonstrating steps at the interface of the Pt seed-FePt bottom electrode (denoted schematically by red lines). (b) Image constructed from the power-spectrum of (a) using the FePt (002) reflection (perpendicular to growth direction), which highlights antiphase boundaries, as shown, for example, in the region of the red oval.
(Left) Processed HAADF-STEM image of the FePt/MgO/FePt interfaces, inset: image simulation of an Fe-terminated interface and atomic-column steps at the interface between barrier and electrode. (Right) Intensity line scans along the Pt, Fe, and MgO crystallographic planes, marked schematically by the green rectangles in the HAADF-STEM image. The image intensity differences demonstrate two crystallographic planes (line scans #5 and #6), which cannot be attributed either to the FePt electrode or MgO barrier.
(Left) Example of relative Fe and O composition across the bottom FePt/MgO interface (from the area of the dashed yellow rectangle, right) calculated using the Fe L and O K core-loss edges in EEL spectra when recording the HAADF-STEM image (right) using the "StripeSTEM" approach.
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