LASER-ABLATION DEPOSITION OF CU-NI AND AG-NI FILMS - NONCONSERVATION OF ALLOY COMPOSITION AND FILM MICROSTRUCTURE

Laser ablation deposition was used to grow polycrystalline Cu-Ni and Ag-Ni thin films on amorphous substrates at room temperature. X-ray diffraction was employed to determine the phases present and the residual macrostress and to analyze the structural imperfection in terms of crystallite size and microstrain. For confirmation and complementary microstructural data transmission electron microscopy was applied. Analysis of the gross composition was achieved by electron probe microanalysis and x-ray fluorescence. The films contained substantially less Cu and Ag than the targets, which was caused by preferential scattering of ablated Cu and Ag species upon incidence at the growing films. The Cu-Ni films were entirely composed of a CuxNi1-x solid solution. The Ag-Ni films were composed of a AgxNi1-x solid solution and of pure Ag and pure Ni. The nonequilibrium AgxNi1-x solid solution could contain up to 44 at. % Ag. The residual macrostress in the Cu-Ni films was compressive, whereas it was tensile in the Ag-Ni films. The occurrence of these stresses could be interpreted as due to the combined effects of atomic peening and cooling after deposition and, in the case of the Ag-Ni films, of stress relaxation by partial decomposition of the AgxNi1-x solid solution during film growth. The microstrains in the AgxNi1-x solid solutions were higher than in similarly prepared pure elemental Ag and Ni films. Compositional inhomogeneity of the AgxNi1-x solid solution crystallites contributed in particular to this effect. The strain-free lattice parameters of the solid solutions were found to be in fair agreement with those predicted by Vegard's law.