Density and defects in thin metal films using x‐ray reflectivity and variable‐energy positrons

摘要

X‐ray reflectivity has been used to determine the absolute metal density for both metals in bilayers of Al on top of Co, Cr, Cu, Mn, Ni, and Pd. A large variation in density is found with an observed range of 0.87–1.0 of bulk values. The results can be correlated with changes in the defect character as determined by variable‐energy positron measurements. The size of the open volume defects systematically increases as the metal density decreases. A distinct densification of the Co layer was observed after annealing, and was accompanied by a corresponding reduction in the average size of the defects. There seems to be at least a partial correlation of the density with the melting point of the metals, although other factors such as the crystal structure are likely important. These results also demonstrate the application of x‐ray reflectivity and variable‐energy positrons to studies of thin metal films, and a discussion of their potential utility is included.