INTERFACE EFFECTS AND ELASTIC-CONSTANTS OF AG/NI SUPERLATTICES STUDIED BY BRILLOUIN-SCATTERING

The elastic properties of sputter-deposited Ag/Ni superlattices have been studied by means of the Brillouin light scattering technique. Measurements have been taken on both free-standing and glass-supported superlattices, the former deposited at 100 K, the latter at 300 K. The two effective elastic constants c11 and c44 have been determined on specimens 5-mu-m thick for different superlattice periods; c44 decreases by almost 40% as the bilayer periodicity decreases from 19 to 1.3 nm, while c11 shows no appreciable variation. Measurements performed on supported specimens, 0.5-mu-m thick, enabled us to get information also on the constant c33, which exhibits a monotonic increase with period. The elastic anomalies found can be related to the appreciable lattice distortion observed by x-ray diffraction experiments. Both Brillouin scattering and x-ray analysis have shown that the interface quality improves appreciably when the temperature of deposition is lowered from 300 to 100 K.