Microindentation hardness testing of different composite systems with thin electrodeposited nickel and copper films

Abstract

Thin Ni and Cu films with fine-grained structures have been electrodeposited from self-made sulphamate-based and sulphate-based electrolytes, respectively. DC electrodeposition of Ni films was performed on single crystal Si wafers with different orientations named (100) and (111), and electrodeposition of Cu films was performed on massive electrodeposited Ni films as the substrates. In order to investigate the influence of the microstructure of the substrates and Ni and Cu thin films on mechanical properties of these composite structures, Vickers microhardness testing for different loads was done. For any composite system of thin film on a substrate, there is a critical indentation depth,1 when a measured hardness value is not the hardness of the electrodeposited film, but the so-called "composite hardness", because the substrate also participates in the plastic deformations during the indentation process. Composite hardness model of Chicot-Lesage was chosen and applied to the experimental data in order to analyse and determine the absolute film hardness. Further analysis of work hardening parameter (t/d)m, that can express the difference in tendency of the composite hardness with the indentation load, was performed for the above-mentioned composite systems.