Characterizing Interfacial Fracture Toughness Using AFM

Abstract Reliability of thin polymer films is strongly dependent on interfacial adhesion. This paper concerns the application of indentation combined with atomic force microscopy (AFM) for the evaluation of polymer-non-polymer adhesion. Interfacial toughness calculations have been made using AFM measurement of geometry of delaminations induced by indentation. Fracture surfaces characterized with AFM are also presented here. The interface chosen for study is that between polystyrene (PS) and a glass substrate. Spin coating has been used to prepare PS films. PS, dissolved in toluene, was spun onto the soda-lime glass and then dried at 60°C for 3h to remove residual solvent. The thickness of the PS film was approximately 660nm. To enhance the driving force for delamination, poly(methyl methacrylate) (PMMA) overlayers were applied on top of the PS films. The PMMA overlayer, of thickness approximately 1.5 μm, was first solvent cast onto a second glass slide, floated off the glass onto deionized water, and then laid on top of a first glass substrate which had been coated with PS.