Effect of Al2O3/Alucone nanolayered composite overcoating on reliability of Ag nanowire electrodes under bending fatigue

In this study, Al2O3/alucone nanolayered composites were studied as the overcoating for Ag nanowire electrodes with the aim of improving their mechanical reliability. Ultrathin and conformal Al2O3/alucone nanolayered composites with different layer spacings were formed on Ag nanowire electrodes via molecular layer deposition. To evaluate the effect of the different nanolayered composite overcoatings with the different layer spacing on the mechanical reliability of Ag nanowire electrodes, bending fatigue tests were performed on the specimens for up to 300,000 cycles while monitoring their resistance in situ. Ag nanowire electrodes with the nanolayered composite overcoating exhibited considerably smaller increases in resistance under bending fatigue, as compared to those with a single Al2O3 layer. In the nanolayered composites, the increase in resistance was further reduced as the layer spacing was decreased. Microstructural analysis confirmed that the density of propagated cracks in the overcoating layers was lower in the nanolayered composites compared to the single Al2O3 layer, resulting in a smaller increase in the resistance of the nanolayered composites. A finite-element method simulation of the bending of a single Al2O3 layer and nanolayered composites, which were designed to match the characteristics of our experimentally tested samples, indicated stress relaxation at the interfaces of the alucone layer, which strengthens the mechanical reliability of the nanolayered composites.