X-Ray Diffraction by Multilayered Thin-Film Structures and Their Diffusion

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Abstract
Five orders of soft x-ray diffraction by multilayered thin-film structures of Fe and Mg have been observed. The structures consisted of as many as 200 layers of Fe separated by Mg layers, providing layer spacings of 30–50 Å. The diffracting characteristics have been measured for the wavelength range 8.34 to 23.7 Å (AlKα to OKα). The integrated diffracted intensities from Fe–Mg layered structures and multilayered lead stearate soap-film structures are shown to be comparable. A diffracted x-ray peak intensity to background ratio of 80 and a resolution (λ/Δλ) of 25 have been observed for the diffraction of OKα radiation by the Fe–Mg structures. No diffusion in the Fe–Mg layers was detected at room temperature. The diffracted x-ray intensity from similar Au–Mg layered structures decreased to one-half in 15 days at room temperature because of interdiffusion. Diffusion in the Au–Mg layered system may be described by an effective interdiffusion constant that satisfies the equation Deff=4.3×10−9 exp[−18.3 kcal/(RT)] cm2 sec−1 for the temperature range 23–100°C. For Fe–Mg layered structures an effective interdiffusion constant Deff=7.9×10−20 cm2 sec−1 was measured at 260°C.