Despite growing efforts to replace them, transparent conducting oxide layers deposited on polymer substrates are still enjoying a dominant role as the electrode component. This is because of their excellent combination of electrical and optical properties. However, their performance when they are subjected to externally-applied mechanical stresses is limited. Such performance has been extensively investigated for the case of continuous brittle oxide films on polymer substrates. However, there is relatively little work reported to date on the mechanical behavior of patterned conducting layers on compliant substrates.
In this study we report on the mechanical behavior of various patterned indium tin oxide shapes and sizes on polyethylene terephthalate. Micron-sized shapes include squares, circles, and zigzag-based structures. Controlled buckling experiments are performed in-situ using an optical microscope in order to monitor critical strains and potential failure mechanisms. In addition, ITO electrical resistance changes are continuously monitored during deformation. Furthermore, ex-situ characterization of the tested surfaces using scanning electron microscopy is conducted. Higher crack onset values are observed for the smaller size patterns. Also, square-shaped patterns are found to exhibit the lowest crack onset values. SEM observations suggest cracking-driven and buckling-driven delamination during ITO tensile and compressive buckling mode respectively. In both cases, failure is observed to initiate from the pattern edges.