Strain mapping on gold thin film buckling and siliconblistering

Stress/Strain fields associated with thin film buckling induced by compressive stresses or blistering due to the presence of gas bubbles underneath single crystal surfaces are difficult to measure owing to the microscale dimensions of these structures. In this work, we show that micro Scanning X-ray diffraction is a well suited technique for mapping the strain/stress tensor of these damaged structures

On the relation between Frank-Read source nature and fine slip line structure

Slip patterning is influenced by both the distribution of Frank-Read sources in the bulk crystal and the dislocation interactions before emerging at the surface. The fine structure of slip lines is also highly dependent on the intrinsic nature of Frank-Read sources and particularly on their pinning points and external dislocation network, which is often not considered. In this paper, different types of Frank-Read sources are reviewed and the direct effects are described and discussed of these dislocation multiplication mechanisms on the step fine structure at the surface

Atomic force microscopy investigation of buckling patterns of nickel thin films on polycarbonate substrates

The evolution of buckling patterns of nickel thin films have been studied in situ by atomic force microscopy during cyclic tests composed of uniaxial compression followed by release of the external applied stress. After the first strain cycling, buckling structures evolve from straight-sided wrinkles to varicose patterns characterized by a debuckling of some parts of the film. Further cycling tests reveal that rebonding of the film on its substrate does not occur once decohesion has taken place.Anglai

Buckle depression as a signature of Young’s modulus mismatch between a film and its substrate

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Interacting straight-sided buckles: An enhanced attraction by substrate elasticity

International audienceInteraction between two straight-sided buckles propagating in opposite directions has been investigated by atomic force microscopy. Below a critical separation distance, it is observed that the two buckles are attracted towards each other once their fronts have crossed. A mechanical analysis using finite element simulations has shown that the buckle interaction is strongly influenced by the substrate elasticity. The deviation of the two buckles from their initial straight propagation is discussed at the light of mode mixity mappings extracted from finite elements simulations along the crack path of the two interacting buckles. Finally, a phase diagram depending on both the separation distance and the film/substrate elastic mismatch is proposed, in good agreement with the experimental results

Stability of wrinkling patterns: from straight-sided to worm-like structures

The stability of compressed thin films on substrates is discussed in the frame of the Föppl-Von Karman theory of thin plate buckling. The destabilization from pre-existing straight-sided to worm-like patterns is investigated and a critical stress is determined, above which the morphological change of the film occurs. Experimental investigations by atomic force microscopy have been also conducted and the different stages of this evolution have been characterized

Interactive study of straight-sided buckling patterns in thin films under compressive stress

In situ atomic force microscopy observations have been carried out of thin films under external compressive stress. Straight-sided buckling patterns arise perpendicular to the compression axis which tend to attract one another during propagation a few hundred nanometers apart. The mechanisms whereby these debonding patterns interact have been investigated taking into account the elastic energy of both the film and the substrate. The equilibrium distance between two straight-sided wrinkles has been determined; good agreement has been obtained between the experimental results and the mechanics involved