Diffusion induced grain boundary migration in [formula omitted] and [formula omitted] thin films

Abstract

Diffusion induced grain boundary migration was studied by transmission electron microscopy and scanning transmission electron microscopy in the gold-rich layer of thin film Au Cu and Au Ag diffusion couples possessing grain boundary structures of controlled geometry. When either copper or silver was diffused along the boundaries in the gold-rich layer at temperatures where lattice diffusion was essentially frozen out, the boundaries were induced to migrate leaving alloyed zones behind in their wakes. The structures and compositions of the alloyed zones and the kinetics of the migration under various conditions were studied in detail in a large number of [111] and [001] tilt boundaries in Au Cu couples and [111] tilt boundaries in Au Ag couples. The phenomenon was also studied more indirectly by Auger sputter depth profiling at random boundaries in Au Ag couples. A number of the results obtained in the work have been utilized by Balluffi and Cahn [ Acta metall. 29, 493 (1981)] in the development of their proposed model for diffusion induced grain boundary migration in which the migration occurs by the climb of grain boundary dislocations and their associated steps as a result of an inequality in the boundary diffusivities of solute and solvent atoms. Additional aspects of the work are discussed.