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Characterization of an ultra-thin Fe layer using in-plane scattering and X-ray reflectivity


The interest in ultra-thin magnetic films has been steadily increasing since they are the building blocks of spintronic applications such as data storage devices and magnetic random access memory. However, structural characterization of the interfaces of ultrathin films with possible chemical reactions and formation of new crystalline phases has always been a challenge in materials research.


The SmartLab multi-purpose diffraction system configured with a state of the art independent in-plane scanning arm is best suited for the study of ultra-thin films. The example shown here is a 2 nm elemental Fe film deposited on top of 10 nm of CuO on silicon. The sample was annealed in vacuum at 300°C for 30 minutes. The measurement was performed with a 2.2 kW Cu sealed-tube X-ray source.

Figure 1 shows the measured in-plane XRD profile and the identified phases. Clearly, the 2 nm elemental iron has been oxidized to Fe₃O₄ while the CuO has been reduced to elemental copper due to the chemical reactions at the interfaces.

In-plane XRD profile and identified phases
Figure 1: In-plane XRD profile and phase identification of the annealed 2 nm Fe film on top of 10 nm CuO. The iron layer is oxidized while the CuO layer is reduced.

Figure 2 shows the X-ray reflectivity (XRR) profile of the same sample along with a simulation of the calculated layer structure. The XRR analysis confirms the in-plane XRD results and provides additional information about the Fe3O4; and copper layer thicknesses.


X-ray reflectivity (XRR) profile
Figure 2: X-ray reflectivity measured data and simulation/refinement of the calculated layer structure.