Enhanced Mechanical Stability and Scratch Resistance of Mesoporous Aluminosilicate Thin Films

Mesoporous coatings are widely used in industries such as optics, display technologies, photovoltaics, and bioengineering, due to their attractive properties such as high surface to volume ratio and excellent mass and electron transport characteristics. While structural parameters and material composition can be routinely tailored to the respective applications, improvements of their mechanical properties and robustness, essential for their long-term performance, remain a challenge. Herein, we provide a comprehensive study on the relationship between the degree of porosity, type of material processing and resulting mechanical properties for the use case of mesoporous aluminosilicate thin films that were co-assembled via a sacrificial block copolymer structure-directing agent. Several routes, including the introduction of chelating agents on the precursor solution, a two-step calcination process, and a variation over the aluminium content were explored with the objective of improving the scratch resistance and mechanical properties of the final mesoporous thin film. Pencil hardness tests were combined with atomic force microscopy analysis to investigate the macroscopic scratch resistance, i.e. plastic deformation. Ellipsometric porosimetry served to determine the elastic deformation of the nanoscopic architecture via measurement of the Young’s modulus. Our comparative investigation highlights the promising role of organic chelating agents to the sol-gel formulation to slow down the hydrolysis of the aluminium precursor, which facilitated improvements of the mechanical performance close to industrial standard.