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

By use of nanoindentation, the hardness was measured in dc-magnetron-sputte red Ag/Ni, Au/Ni and Cu/Ni multilayers as a function of the modulation-peri od. In a limited modulation-period range, the expression k Lambda (-n), whe re k and n are fitting parameters and Lambda is the modulation period, was fitted to the curves of hardness versus modulation period for the three typ es 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 significan t difference exists between the lattice parameters, shear moduli, morpholog ies and microstructures of the two systems. The results are discussed consi dering theoretical models and published experimental data.