Hardness in Ag/Ni, Au/Ni and Cu/Ni multilayers

Abstract

By use of nanoindentation, the hardness was measured in dc-magnetronsputtered Ag/Ni, Au/Ni and Cu/Ni multilayers as a function of the modulation-period. In a limited modulation-period range, the expression kA ^-n , where k and n are fitting parameters and A is the modulation period, was fitted to the curves of hardness versus modulation period for the three types of multilayer. The exponent n of Ag/Ni was found to deviate by a factor of three from the n value of Au/Ni, which is surprising since no significant difference exists between the lattice parameters, shear moduli, morphologies and microstructures of the two systems. The results are discussed considering theoretical models and published experimental data.