Mechanical adhesion of SIO2 thin film on a polymeric substrate under compressive stress

Caroline Ho (1, 2) , Anita Dehoux (2) , Loïc Lacroix (1) , Joël Alexis (1) , Olivier Dalverny (1) , Sébastien Châtel (2) , Bruce Faure (2)

1 LGP - Laboratoire Génie de Production
2 Essilor International

To ensure good adhesion between a 200 nm silicon dioxide layer and a 4.5 μm thick hardcoat polymeric coating, a better understanding of mechanisms of adhesion at this interface is needed. To reach this purpose, quantification of adhesion is performed by analyzing SiO2 buckle morphologies generated under compressive stress. This adhesion test was chosen for its representativeness of defects observed in real life. Interfacial toughness can be determined by applying Hutchinson & Suo model. This analytical model involves accurate value of elastic modulus Ef of SiO2 thin film. Small dimensions at stake make characterization of elastic modulus challenging. First part of the study focuses on using both nano-indentation and AFM to attempt assessment of SiO2 thin film elastic modulus. Results showed significant influence of substrate for both techniques. Impact on mechanical properties between SiO2 thin films with different intrinsic stresses was also investigated and suggests that higher density of SiO2 thin film leads to higher elastic modulus. Compression tests resulted in formation of straight-sided buckles that evolve into telephone cords upon unloading. Numerical simulation and Digital Image Correlation were implemented to ensure homogeneous strain of substrate and favor regular distribution of buckles. Values of energy release rates of SiO2 / Hardcoat range from 2.7 J/m² to 8.9 J/m², depending on moduli values found on wafer or lens substrate.

Mots clés: Oxide thin film; Polymer substrate; Mechanical properties; Adhesion

Domaines: Mécanique des matériaux [physics.class-ph]

Caroline Ho, Anita Dehoux, Loïc Lacroix, Joël Alexis, Olivier Dalverny, et al.. Mechanical adhesion of SIO2 thin film on a polymeric substrate under compressive stress. XXXI International Conference on Surface Modification Technologies (SMT31), Jul 2016, Mons, Belgium. pp.1-10. ⟨hal-02359832⟩