Elucidating the effect of Ag interlayer formation on the intrinsic mechanical properties of free-standing ITO/Ag/ITO thin films

The lack of characterization of the mechanical behavior of brittle indium tin oxide (ITO)-based electrodes has been a core issue for the development of advanced transparent and flexible electronics. In this study, we report the intrinsic mechanical properties of ITO/Ag/ITO (IAI) thin films measured by a free-standing tensile testing method for robust transparent electrodes. To understand the effect of Ag interlayer formation on the mechanical properties, Ag thickness is controlled (8-50 nm) by considering the stage of the film formation. Based on the tensile test, IAI thin films with a film-likely formed Ag interlayer (12-14 nm) exhibited outstanding mechanical robustness compared with island-(8 nm) or film-type (>25 nm) Ag interlayers. Notably, the most superior elongation and tensile strength (0.57 +/- 0.08% and 514.3 +/- 71.5 MPa) are demonstrated for 14 nm-thick Ag interlayer, which is two-fold higher than pristine ITO thin films (0.27% and 264.6 MPa). The study provides intrinsic mechanical property values and fundamental insights into the fracture mechanisms that govern the mechanical behavior of oxide/metal/oxide multilayer thin films, which is valuable for the development of flexible electronics.