In situ investigation of the microstructure evolution in nanocrystalline copper electrodeposits at room temperature

The microstructure evolution in copper electrodeposits at room temperature (self-annealing) was investigated by means of x-ray diffraction analysis and simultaneous measurements of the electrical resistivity as a function of time. In situ studies were started immediately after deposition of the various thick layers and continued with a unique time resolution until stabilization of the recorded data occurred. Independent of the copper layer thickness, the as-deposited microstructure consisted of nanocrystalline grains with orientation dependent crystallite sizes. Orientation dependent grain growth, crystallographic texture changes by multiple twinning, and a decrease of the electrical resistivity occurred as a function of time at room temperature. The kinetics of self-annealing is strongly affected by the layer thickness: the thinner the layer, the slower the microstructure evolution is, and self-annealing is suppressed completely for a thin layer with 0.4μm. The preferred crystallographic orientation of the as-deposited crystallites is suggested to cause the observed thickness dependence of the self-annealing kinetics.