Direct observations of rapid diffusion of Cu in Au thin films using in situ x-ray diffraction

J. W. Elmer, T. A. Palmer, E. D. Specht

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16 Scopus citations

Abstract

In situ x-ray diffraction was performed while annealing thin film AuCu binary diffusion couples to directly observe diffusion at elevated temperatures. The temperature dependence of the interdiffusion coefficient was determined from isothermal measurements at 700, 800, 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 kJmole during this initial stage, which is approximately 0.4× that for bulk diffusion and 0.8× 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 kJmole 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.

Original languageEnglish (US)
Article number102604JVA
Pages (from-to)978-987
Number of pages10
JournalJournal of Vacuum Science and Technology A: Vacuum, Surfaces and Films
Volume24
Issue number4
DOIs
StatePublished - Jul 2006

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films

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