Thermal and radiation-enhanced diffusion in thin films of the order-disorder alloy ${\mathrm{Cu}}_3\mathrm{Au}$ have been analyzed above and below the transition temperature. It is demonstrated that thin films grown by molecular beam epitaxy are uniquely suited for such experiments as the surface provides a dominant and well-characterized sink for migrating defects. The analysis is applied to recent experiments. Quantitative predictions of radiation-enhanced diffusion agree closely with experimental values. Analysis of the tracer-impurity thermal diffusion experiments provide host diffusion coefficients in a temperature regime through the transition temperature which were heretofore unavailable.

• Received 12 October 1998

DOI:https://doi.org/10.1103/PhysRevB.60.881