Deformation modes of nanostructured thin film under controlled biaxial deformation

Abstract

This paper reports on the mechanical behaviour of nanostructured W/Cu thin films deposited on Kapton ® under controlled biaxial loadings thanks to a biaxial testing device developed on DiffAbs beamline at SOLEIL synchrotron (Saint-Aubin, France). In situ tensile tests were carried out combining 2D synchrotron x-ray diffraction (XRD) and digital-image correlation (DIC) techniques. First, the elastic behaviour of the composite metallic film -polymeric substrate was investigated under equi-biaxial and non-equibiaxial loading conditions. The results show that the strain measurements (in the crystalline film by XRD and the substrate by DIC) match to within 10 -4 . This result demonstrates the full transmission of strains in the elastic domain through the film-substrate interface and thus a good adhesion of the thin film to the substrate. The second part of the paper deals with higher strains response under equi-biaxial tensile tests. The elastic limit of the nanostructured W/Cu thin films was determined at the bifurcation point between strains obtained by XRD and DIC. Deformation mechanisms such as strain localisation and film fragmentation are proposed.

Comparative study of the mechanical properties of nanostructured thin films on stretchable substrates

“…The studied samples show obviously three distinct deformation regimes as observed in previous studies of metal thin films. [38][39][40][41] The elastic domain was followed by energy dissipation in the film volume as the film/substrate composite was further strained until saturation (plateau stress). The obtained elastic limit for each coating is determined in view of the microstructure and it is clear that the combination of W and Cu in the form of a nanostructured composite resulted in an improved elastic limit.…”

“…The total stress within Cu thin film is tensile (positive slope) and increases progressively during the test. As shown in a previous work, 38 XRD measurements have been compared to those obtained by DIC in order to determine the elastic limit of the film which is defined as the point from which lattice strain and true strain differ by more than 0.02%.…”

Voltage-induced strain control of the magnetic anisotropy in a Ni thin film on flexible substrate

“…In this study, the film surface was spraypainted with a speckle pattern to generate a contrast in the uniform specimen face. Hence, from the measured strain fields we can estimate the mean in-plane strains ε XX and ε Y Y , that cannot be straightforwardly attained with other techniques such as x-ray diffraction [29].…”

Load Sharing Phenomena in Nanoscale Cu/Nb Multilayers

“…[4,5] However, as the individual layer thicknesses decrease below 20 nm, the deformation behavior becomes more difficult to observe. [9,[11][12][13][14][15][16] NMMs with layer thicknesses of approximately 20 nm have been previously studied, although the influence of layer thickness was not investigated, [17,18] while a study of W/Cu NMMs with varying layer thicknesses focused on the elastic properties and interfacial mixing in the samples. [6,7] However, other in situ techniques are needed to characterize the global behavior of these materials.…”

“…[8][9][10] Several NMMs have been previously tested with this method, but those studies generally concentrated on the technique itself or investigated relatively thick layers. [9,[11][12][13][14][15][16] NMMs with layer thicknesses of approximately 20 nm have been previously studied, although the influence of layer thickness was not investigated, [17,18] while a study of W/Cu NMMs with varying layer thicknesses focused on the elastic properties and interfacial mixing in the samples. [19] In contrast, in this study we explore the deformation of ultrathin (2-20 nm thick) layers as a function of the layer thickness, with the aim of isolating the mechanical contribution of each material in the NMM system.…”