Impact of the brittle layers on the electrical and mechanical behaviours of 18 nm Ag layers in indium tin oxide-silver stackings

Abstract

The electrical and mechanical properties of indium tin oxide (ITO) and silver (Ag) multilayers deposited on polyimides (PI) are studied. From the electrical point of view, the multilayer performs initially like the Ag layer, as seen in the $R$-sheet and in the gauge factor, and behaves during biaxial tensile tests according to the mechanical properties of this 18 nm Ag layer. The mechanical properties strongly change for different multilayer architectures. For example, the ITO/Ag/ITO/PI sample shows an elastic regime, whereas plasticity occurs immediately in Ag/ITO/PI, ITO/Ag/PI and Ag/PI samples. Moreover, the Ag layer sustains a stress of almost $500\mathrm{MPa}$ before cracking in the first case, but no more than $200\mathrm{MPa}$ in the second. This shows how the mechanical behaviour of ultra-thin silver layers is dictated by the interfaces, that may be soft (as with air or polyimide) or hard (amorphous or crystalline).