THERMAL-EXPANSION OF NI CU MULTILAYERS

The coefficient of thermal expansion of electrodeposited Ni/Cu multila yers was obtained by measuring the evolution of membrane resonances an d hence the tension as a function of temperature. The apparent thermal expansion coefficient of the multilayer membranes increases as the in terface density of the multilayers increases. This increase is analyze d in terms of stress relaxation resulting from sliding of nonperfectly bonded interfaces. The analysis permits the normalization of all ther mal expansion data of the Cu/Ni multilayers with layer thicknesses ran ging from 20 to 800 nm but not of the thinnest layers, 2 nm thick. The results are consistent with the idea that interfacial adhesion improv es as the layer thickness becomes very small, favoring epitaxial growt h.