Nanomechanical characterization of porous anodic aluminum oxide films by nanoindentation

• Deposition of porous anodic aluminum oxide (AAO) films on glass
• Nanoindentation characterization of the substrate and porous AAO films
• Introduction of spring elements in finite element analysis for improving simulation accuracy
• Modeling and analysis of the effects of the substrate and the porous film structure

Nanostructured thin films have gained great interests in recent years due to their significantly enhanced properties and great potential for various applications. Nanoindentation techniques are commonly used to measure nanomechanical properties of thin films and the surface layers of bulk materials. In this article, nanoindentation tests coupled with computer modeling were proposed to characterize nanostructured porous anodic aluminum oxide (AAO) films grown on glass. A three-dimensional nanoindentation model was developed. The Young's modulus and hardness were measured by nanoindentation using a Berkowich pyramidal sharp tip indenter. The effects of the substrate and porous structure of the film on the coating measurements were investigated. The dilemma for extracting the mechanical properties of a porous structural film in nanoindentation has been pointed out, and an alternative approach of combined modeling/experimental provided a justification by considering the porous structure of the film and minimizing the influence of the substrate. Computer modeling results were validated by experimental data.