Interdiffusion in composition-modulated copper-gold thin films

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Abstract
Vapor‐deposited Cu‐Au thin films were produced containing composition modulations with wavelengths between 8 and 26 Å. The modulations produced satellite peaks in the x‐ray diffraction patterns. Amplification factors and the corresponding diffusion coefficients were obtained by measuring the decay rate of the satellite intensities. The amplification factor reached a maximum at 17 Å and decreased at both shorter and longer wavelengths. Interdiffusion coefficients between 10−21 and 10−19 cm2/sec were measured over the temperature range 200–260 °C. The effective diffusion coefficient is linearly dependent on the function B2(λ) for λ≳10 Å. From the wavelength dependence of the measured diffusivities, a gradient‐energy coefficient of −4.7×10−6 erg/cm was obtained and is in good agreement with theoretical estimates. These experimental results were compared with the predictions from a proposed model for diffusion on cubic lattices.