Nanoscale stability of two- and three-dimensional defects in Cu/Ag–Mo thin films

A comparative study of the thermal stability of nanocrystalline Cu–Mo and Ag–Mo alloy thin films was performed. Phase decomposition, texture evolution, grain coarsening and segregation of Mo to planar faults of both films, before and after heat treatment, were studied using X-ray diffraction measurements and (high-resolution) transmission electron microscopy with energy-dispersive spectroscopy. The evolution of stress/strain in the thin films was traced by in situ X-ray diffraction measurements. The segregation of Mo solute atoms at twin boundaries in both films already occurs at room temperature. By first segregation and then precipitation of Mo atoms at grain boundaries, the columnar grain microstructure is preserved upon heat treatment. In the case of Ag–Mo thin films, the twin boundaries are also more or less preserved at elevated temperature, but in the case of Cu–Mo thin films the annihilation of twin boundaries takes place concomitantly with the precipitation of Mo in columnar grain interiors.