Hiroyuki Hirakata

Effect of residual stress on delamination from interface edge between nano-films

Abstract The focus in this study is on the effect of residual stress on the delamination crack initiation from the interface edge between thin films, Cu/TiN, where the stress is intensified by the free edge effect. The delamination tests, where the mechanical stress is applied on the interface, show that the specimen with the thinner Cu film has an apparently higher strength at the interface edge. The residual stress in the films is then evaluated by curvature measurement of film/substrate coupon and the influence on the delamination is analyzed. The residual stress increases with the increase of film thickness and remarkably intensifies the stress near the edge. By superimposing the contributions of the applied load and the residual stress, a good agreement is obtained in the normal stress intensity near the interface edge at the delamination independent of the Cu thickness. This signifies that the combination of intensified stresses due to the applied load and the residual stress governs the crack initiation at the interface edge, and the toughness at the interface edge is evaluated by the stress intensity factor on the basis of the fracture mechanics concept.

Direct observation of the thickness effect on critical crack tip opening displacement in freestanding copper submicron-films by in situ electron microscopy fracture toughness testing

We evaluated the thickness effect on fracture toughness in freestanding Cu films with thicknesses of approximately 100, 500, and 2600 nm, on the basis of crack tip opening displacement (CTOD) concept by means of in situ (field emission scanning electron microscopy) FESEM and (transmission electron microscopy) TEM fracture toughness testing. During testing, an acute pre-crack tip blunted gradually and necking deformation in the out-of-plane direction occurred in the region ahead of the crack tip in all the specimens. A crack then initiated from the pre-crack tip and propagated along the necking region resulting in chisel point fracture. Since the small scale yielding condition was not satisfied in the 500 and 2600 nm specimens, the critical CTOD,

DELAMINATION TEST AND THE EFFECT OF FREE EDGE ON INTERFACE STRENGTH OF PZT THIN FILMS

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Fabrication and mechanical properties of column–particle nanocomposites by multiscale shape-assisted self-assembly

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Increase of Stress Intensity near Free-Edge of Elastic-Creeping Bi-Material Interface under a Sustained Load

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In situ observation of interfacial fracture in low-dimensional nanostructures

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