Investigation Of Mechanical And Interfacial Properties Of Nanoscale Films Based On Buckling-delamination

The film/substrate structures realized system miniaturization and informatization effectively, are widely used in microelectronics, aerospace, biology, medical science and so on. The failure modes, including film fracture, delamination and buckling, will appear in the work process when structures under external load. Damage of interface has a serious impact on service performance of structures. A experimental and numerical work based on buckling-delamination was carried to investigate the mechanical and interfacial properties of the nano-films deposited on substrate.In situ observation of straight-sided buckling initiation and propagation on the film has been carried in the process of the film/PMMA substrate structure under uniaxial compression load. The facts have been studied by the theory of propagation. In the process of unloading, straight-sided buckles evolve to telephone-cord wrinkles, finally, all translate to bubbles.The research results show that instability of straight-sided buckles and evolution of failure modes is relate to the residual stress, stress relief of film, the poisson ratio of film and substrate.The study on the mechanical properties of bubbles in the influence of interface was performed by nano-indentation method. The comparison of AFM with indentation measurement results of bubbles was obtained to measure the height of bubbles. The elastic modulus and stiffness results of bubbles are studied for films with thickness of 300 nm and 400 nm. The study results show that the stiffness of bubbles decreases with increasing height, but increase with thickness. The role of the interface makes elastic modulus results larger, stiffness and bearing capacity of film/substrate structures stronger.The interfacial adhesion energy of the film/substrate structures is one of the most important performance parameters of the film device. Based on the influence of interface, a theoretical model of film/substrate system for characterion of interfacial properties is proposed. Nano-indentation is performed on delaminated region and perfect region. The difference of plastic work between two regions is adopted to determine the interfacial energy release rate. The ratio of hardness to elastic modulus is studied in the function of the indentation depth to determine the critical delaminated depth.The cohesive model was developed to describe the adhesion relationship between films and substrates. Using the finite-element method, we investigated the process of film buckling-delamination and propagation. The research of interface parameters effecting on interface failure behavior was then carried out. Comparison of experimental and simulation results for interfacial crack length and indentation curves is used to verify and replenish the experimental results of interfacial performance parameters.