DENSITY AND DEFECTS IN THIN METAL-FILMS USING X-RAY REFLECTIVITY AND VARIABLE-ENERGY POSITRONS

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.