Applications of an energy-dispersive pnCCD for X-ray reflectivity: Investigation of interdiffusion in Fe-Pt multilayers

A frame store pn-junction CCD (pnCCD) detector was applied to study thermally induced interdiffusion in Fe/Pt thin film multilayers (MLs) in a temperature range between 300 and 585 K. Based on the energy resolution of the detector the reflectivity was measured simultaneously in a spectral range between 8 keV < E < 20 keV including the Pt L-edge energies close to 11.5 keV. Above T - 533K we find a strong drop of intensities at 1st and 2nd order ML Bragg peak interpreted mutual interdiffusion. Considering a simulated model of interdiffusion it has been found that the concentration of iron that diffuses into the platinum sub layers is higher than that of platinum into iron. The time dependence of inter diffusion was also calculated in the range of 533-568K and was described by the Arrhenius equation D(T) - D(0) exp(-H(a)/k(B)T). The activation energy for the MLs used [Fe 1.7 nm/Pt 2 nm](50) was found to be 0.94 +/- 0.22 eV. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim