Direct Observations of Rapid Diffusion of Cu in Au Thin Films using In-Situ X-ray Diffraction Page: 3 of 35
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Direct Observations of Rapid Diffusion of Cu in Au Thin Films
using In-Situ X-Ray Diffraction
J. W. Elmer and T. A. Palmer
Lawrence Livermore National Laboratory, Livermore, CA, 94551, USA
E. D. Specht
Oak Ridge National Laboratory, Oak Ridge, TN, 37831, USA
Synchrotron Radiation, Interdiffusion, Grain Boundary Diffusion, Thin Films, Binary Alloys,
In-situ x-ray diffraction was performed while annealing thin-film Au/Cu binary diffusion
couples to directly observe diffusion at elevated temperatures. The temperature dependence of
the interdiffusion coefficient was determined from isothermal measurements at 700 C, 800 C,
and 900 C, where Cu and Au form a disordered continuous face centered cubic solid solution.
Large differences in the lattice parameters of Au and Cu allowed the initial diffraction peaks to
be easily identified, and later tracked as they merged into one diffraction peak with increased
diffusion time. Initial diffusion kinetics were studied by measuring the time required for the Cu
to diffuse through the Au thin film of known thickness. The activation energy for interdiffusion
was measured to be 65.4 kJ/mole during this initial stage, which is approximately 0.4x that for
bulk diffusion and 0.8x that for grain boundary diffusion. The low activation energy is attributed
to the high density of columnar grain boundaries combined with other defects in the sputter
deposited thin film coatings. As interdiffusion continues, the two layers homogenize with an
activation energy of 111 kJ/mole during the latter stages of diffusion. This higher activation
energy falls between the reported values for grain boundary and bulk diffusion, and may be
related to grain growth occurring at these temperatures which accounts for the decreasing
importance of grain boundaries on diffusion.
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Elmer, J W; Palmer, T A & Specht, E D. Direct Observations of Rapid Diffusion of Cu in Au Thin Films using In-Situ X-ray Diffraction, article, November 28, 2005; Livermore, California. (digital.library.unt.edu/ark:/67531/metadc879360/m1/3/: accessed June 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.