Plane-strain, buckling-driven delamination of thin films: Model experiments and mode-II fracture
TL;DR: In this article, a series of model experiments have been conducted to compare observations on buckling-driven delamination of thin films under plane-strain compression with an existing analysis.
Abstract: A series of model experiments have been conducted to compare observations on buckling-driven delamination of thin films under plane-strain compression with an existing analysis. The results are consistent within the range considered by the theory, which applies when the delamination crack is open to the tip. However, the observations indicate that delamination can occur beyond this range, when the crack tip is closed and undergoing mode-II advance. The theory was extended to incorporate the effect of a contact region in which frictional effects shields the crack tip. A comparison of the analysis with the data indicates that the frictional stress required to explain the apparent toughness observed in this regime is larger than the shear yield strength of the interface. It is inferred that large-scale plasticity may have a significant effect on the results, but this effect has not been included in the analysis.
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02 Feb 2004TL;DR: The role of stress in mass transport is discussed in this article, where the authors consider anisotropic and patterned films, buckling, bulging, peeling and fracture.
Abstract: 1. Introduction and overview 2. Film stress and substrate curvature 3. Stress in anisotropic and patterned films 4. Delamination and fracture 5. Film buckling, bulging and peeling 6. Dislocation formation in epitaxial systems 7. Dislocation interactions and strain relaxation 8. Equilibrium and stability of surfaces 9. The role of stress in mass transport.
1,562 citations
TL;DR: In this article, four major adhesion mechanisms have been analyzed: capillary forces, hydrogen bridging, electrostatic forces and van der Waals forces, and they have been successfully reduced.
Abstract: Due to the smoothness of the surfaces in surface micromachining, large adhesion forces between fabricated structures and the substrate are encountered. Four major adhesion mechanisms have been analysed: capillary forces, hydrogen bridging, electrostatic forces and van der Waals forces. Once contact is made adhesion forces can be stronger than the restoring elastic forces and even short, thick beams will continue to stick to the substrate. Contact, resulting from drying liquid after release etching, has been successfully reduced. In order to make a fail-safe device stiction during its operational life-time should be anticipated. Electrostatic forces and acceleration forces caused by shocks encountered by the device can be large enough to bring structures into contact with the substrate. In order to avoid in-use stiction adhesion forces should therefore be minimized. This is possible by coating the device with weakly adhesive materials, by using bumps and side-wall spacers and by increasing the surface roughness at the interface. Capillary condensation should also be taken into account as this can lead to large increases in the contact area of roughened surfaces.
543 citations
TL;DR: In this paper, the topology of the telephone cord buckling of compressed diamond-like carbon (DLC) on glass substrates has been characterized with atomic force microscopy (AFM) and with the focused ion beam (FIB) imaging system.
Abstract: The topology of the telephone cord buckling of compressed diamond-like carbon (lms (DLC) on glass substrates has been characterized with atomic force microscopy (AFM) and with the focused ion beam (FIB) imaging system. The pro(les of the several buckles have been measured by AFM to establish the symmetry of each repeat unit, revealing similarity with a circular buckle pinned at its center. By making parallel cuts through the buckle in small, de(ned locations, straight-sided buckles have been created on the identical (lms, enabling the residual stress in the (lm to be determined from the pro(le. It has been shown that the telephone cord topology can be e;ectively modeled as a series of pinned circular buckles along its length, with an unpinned circular buckle at its front. The unit segment comprises a section of a full circular buckle, pinned to the substrate at its center. The model is validated by comparing radial pro(les measured for the telephone cord with those calculated for the pinned buckle, upon using the residual stress in the (lm, determined as above. Once validated, the model has been used to determine the energy release rate and mode mixity, G( ). The results for G( ) indicate that the telephone cord con(guration is preferred when the residual stress in the DLC is large, consistent with observations that straight-sided buckles are rarely observed, and, when they occur, are generally narrower than telephone cords. Telephone cords are observed in many systems, and can be regarded as the generic morphology. Nevertheless, they exist subject to a limited set of conditions, residing within the margin between complete adherence and complete delamination, provided that the interface has a mode II toughness low
222 citations
TL;DR: In this article, the expected failure mechanisms of edge-delamination and bucklingdelamination are addressed at the interface between the bond coat and the TGO, where low inplane elastic moduli of the porous zirconia layer promote the latter, but suppress the former.
190 citations
Cites background from "Plane-strain, buckling-driven delam..."
...It neglects the e ect of frictional stresses that arise when the crack is strictly mode II (Thouless et al., 1992)....
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...It neglects the eect of frictional stresses that arise when the crack is strictly mode II (Thouless et al., 1992)....
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TL;DR: In this article, it was shown that unless the substrate is at least as stiff as the film, the energy stored in the substrate contributes significantly to the energy release rate of film delamination under compression either with or without cracking.
Abstract: It is shown that unless the substrate is at least as stiff as the film, the energy stored in the substrate contributes significantly to the energy release rate of film delamination under compression either with or without cracking. For very compliant substrates, such as polyethylene terephthalate (PET) with a indium tin oxide (ITO) film, the energy release rate allowing for the deformation of the substrate can be more than an order of magnitude greater than the value obtained neglecting the substrate's deformation. The argument that buckling delaminations tunnel at the tip rather than spread sideways because of increase in mode-mixity may need modification; it is still true for stiff substrates, but for compliant substrates the average energy release rate decreases with delamination width and the limitation in buckled width may be due to this stability as much as the increase in mode-mixity.
190 citations
Cites background from "Plane-strain, buckling-driven delam..."
...Under applied or residual compressive strain, a delaminated buckle can propagate from an edge (Thouless et al., 1992, 1994) or central flaw....
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...An upper limit tob/h occurs when there is compressive contact between the delaminated film and the substrate when friction shields the delaminated tip which has been discussed by Thouless et al. (1992) and Stringfellow and Freund (1993)....
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...Under applied or residual compressive strain, a delaminated buckle can propagate from an edge (Thouless et al., 1992, 1994) or central flaw. Hutchinson and Suo (1991) have shown that for a stiff substrate, the average energy release rate for a straight-sided buckle increases with the width of buckled delamination....
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...frictional effects to occur (Thouless et al., 1992; Stringfellow and Freund, 1993) which are not considered in this paper....
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...SEM picture showing tunnelling delamination-buckle-crack. frictional effects to occur (Thouless et al., 1992; Stringfellow and Freund, 1993) which are not considered in this paper....
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References
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TL;DR: In this paper, a first attempt by a delaminating beam-column was modeled by a fracture mechanics-based energy release rate criterion, where the local delamination growth, stability, and arrest were governed by the fracture mechanics.
666 citations
TL;DR: In this paper, the authors used a combination of fracture mechanics and post-buckling theory to analyze the mechanics of delamination and spelling of pre-compressed films and indented coatings.
553 citations
TL;DR: In this article, a Brazil-nut-sandwich with a crack on a substrate/interlayer interface is developed for fracture testing, and the fracture loading phase is controlled by the angle of diametral compression.
Abstract: A Brazil-nut-sandwich with a crack on a substrate/interlayer interface is developed for fracture testing. The fracture loading phase is controlled by the angle of diametral compression. Interfacial fracture mechanics is summarized and adopted in reporting data. Experiments are conducted with aluminum, brass, steel and plexiglass as substrates and epoxy as interlayer. Interfacial toughness curves are measured for large range of loading phase. Effects of the roughness of the surfaces prior to bonding on the interfacial toughness are demonstrated. Failure patterns for the adhesive structure under different loading modes are observed with a scanning electron microscope. For the metal/epoxy systems, when the remote loading is predominantly mode I, cracks tend to kink out of interfaces and run within the epoxy layer, although the bulk epoxy fracture energy is much higher than the interfacial toughness. At large loading phases, abnormally high apparent toughness is measured. These observations are discussed in the light of crack path selection criteria in adhesive joints and large scale contact zone of crack faces.
390 citations
TL;DR: In this article, the fracture resistance of a model bimaterial interface has been measured for a wide range of phase angles: the measure of the relative crack face sliding and opening displacement near the crack tip.
377 citations
TL;DR: In this paper, the effects of non-planarity on the fracture resistance locus of interfaces has been investigated using a simple model of contacting facets along the crack surface, which resist the motion of the crack surfaces by means of friction and locking and thereby modify the energy release rate at the crack front.
337 citations