From resilience to scratch resistance: engineering the deformation mechanisms of nanostructured surfaces

Nanostructured materials and engineered surfaces have attracted significant attention for their unique physical properties in multiple domains. The structural geometry and material composition have a profound influence on the mechanical behavior of these structures but have yet to be systematically examined. This work investigates the effect of the pillar aspect ratio and intrinsic material properties on the deformation mechanisms of sapphire and silicon nanopillar arrays. Using nanoindentation, the modulus, hardness, and scratch resistance of silicon and sapphire nanopillar arrays with various aspect ratios are characterized. The results indicate that low aspect ratio nanopillar arrays have high hardness and stiffness but are brittle and fail through material fracture. On the other hand, high aspect ratio nanopillars are more resilient and exhibit recoverable deformation through structure buckling and bending. The sapphire nanopillar arrays are more mechanically robust compared to silicon and have modulus and hardness comparable to bulk glass and other scratch-resistant metals. The findings guide the development of mechanically robust nanostructured materials with optimized surface properties and can find applications in nanophotonics, multifunctional surfaces, and nanoscale devices.