Microstructural influence on the cyclic electro mechanical behaviour of ductile films on polymer substrates

When ductile metal films on compliant polymer substrates are strained in tension catastrophic failure can be suppressed by the substrate, thus allowing for their use in flexible electronics and sensors. However, the charge carrying ductile films must be of an optimum thickness and microstructure for the suppression of cracking to occur. Studies of strained films on polymer substrates tend to have more emphasis on the electrical properties and thickness effects than on the film microstructure or deformation behaviour. To address both the electrical degradation and deformation behaviour of metal films supported by polymer substrates two types of combined electro-mechanical in-situ tests were performed. First, is a combination of in-situ resistance measurements with in-situ confocal scanning laser microscopy imaging of the film surface during cycling. The 4 point probe resistance measurements allow for the examination of the changes in resistance with strain, while the surface imaging permits the visualization of extrusion and crack formation. Second, is the combination of in-situ resistance with in-situ X-ray diffraction measurements of the film stresses during cycling. The combination of electrical measurements, surface imaging, and stress measurements allow for a complete picture of electromechanical behaviour needed for the improvement and future success of flexible electronic devices

Annealing effects on the film stress and adhesion of tungsten titanium barrier layers

Tungsten titanium WTi alloys are important barrier materials in microelectronic devices. Thus the adhesion of WTi to silicate glass substrates influences the reliability of these devices. One factor that affects the adhesion of barrier layers are thermal treatments during and after fabrication. To address the impact of annealing, WTi films deposited on silicate glass substrates were subjected to different annealing treatments. The stress development in the WTi film has been monitored with wafer curvature and X ray diffraction. Quantitative measurements of the adhesion energies were performed using scratch testing to induce interface delamination. Imaging with atomic force microscopy provided the dimensions of the buckles to quantify adhesion energies. Focused ion beam crosssections were used to verify the failing interfaces and to inspect any deformation in the film and the substrate caused by scratch testing. It was found that as the annealing duration increased, the residual compressive stresses in the film and the adhesion energy increase

In situ observations of the fracture and adhesion of Cu Nb mulitlayers on polyimide substrates

Cu/Nb nanoscale metallic multilayers have been extensively investigated to understand how their mechanical behavior is influenced by the individual layer thickness. The general observed trend is that the yield stress of the multilayer increases with decreasing layer thickness. Important mechanical behaviors that have not been studied in-depth are the fracture of these multilayers and adhesion energy between the multilayer films and their substrate. Here, the influences of the layer thickness, layer order, and initial residual stresses of Cu/Nb multilayers on polyimide were examined using in-situ x-ray diffraction and confocal laser scanning microscopy under tensile loading. With these techniques, it was possible to calculate the stresses developing in the individual materials and measure buckles that could be used to evaluate the interfacial adhesion. Layer thickness, deposition order, and the initial residual stresses were not shown to influence the initial fracture strains of the Cu/Nb multilayer systems under tensile loading conditions. However, the adhesion energy between the multilayer and substrate was affected by the layer deposition order and by the initial residual stresses. © 2018 Elsevier B.V

Encapsulation Effect on Performance and Stability of Organic Solar Cells

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