Effects of dielectric layer on ductility for dielectric/Au/dielectric multilayers on polycarbonate substrate

Abstract

The ductility of transparent conductive films on polycarbonate (PC) substrate is of great concern as it significantly affects the stability and longevity of aeronautic equipment. Three types of dielectric/Au/dielectric multilayers, including ITO/Au/ITO (IAI), IZO/Au/IZO (ZAZ) and AZO/Au/AZO (AAA) were fabricated to obtain highly ductile films on thick rigid PC substrate. The ductility of multilayers was comparatively investigated using in situ scanning electron microscopy test and in situ electrical resistance test under uniaxial tension. The effect of dielectric layer on ductility was elucidated according to the results of film stress and elastic modulus, and analyzed using the energy release rate approach based on the mechanics model. The results of in situ tests revealed that the crack initiation strain by morphology and the conductive failure strain of AAA were found to be 1.04 ± 0.04% and 1.47 ± 0.07%, which were superior to those of IAI and ZAZ. This result can be attributed to differences in layer stress state and layer-substrate mechanical contrast induced by different dielectric layers. Although AAA has the lower fracture toughness, the higher compressive residual stress and the smaller elastic mismatch give AAA the smallest crack driving force under the same conditions, resulting in excellent ductility.