Long-range chemical interaction in solid-state synthesis: The Kirkendall effect and solid-state reactions in Cu/β-CuZn and Cu/Fe/β-CuZn film systems

The results of the experimental investigations of the solid-state reaction of Cu with β brass, which is associated with the Kirkendall, in Cu/β-CuZn and Cu/Fe/β-CuZn film systems are reported. It has been shown that the initiation temperature of the solid-state synthesis of α brass at the Cu/β-CuZn interface is about 200°C. The chemically inert Fe barrier layers 420 and 850 nm in thickness between the Cu and β-CuZn films do not suppress the solid-state synthesis of the α brass, but increase the initiation temperature to about 250°C. This behavior indicates that the chemical interaction between the Cu and Zn atoms through the chemically inert Fe layer is long-range. The X-ray photoelectron investigations reveal the migration of Zn atoms from the β-CuZn layer through the Fe barrier to the Cu layer. The results are interpreted under the assumption that the migration of Zn atoms in the Kirkendall is initiated by the strong chemical interaction between the Cu and Zn atoms in the Cu and β-CuZn layers, which is due to the synthesis of α brass, rather than by the diffusion random walk, as is commonly accepted at present.