Probing the deformation and fracture properties of Cu/W nano-multilayers by in situ SEM and synchrotron XRD strain microscopy

Nano-scale residual stress depth profiling in Cu/W nano-multilayers as a function of magnetron sputtering pressure

“…These two errors are then combined by following the appropriate error summation rules. Converting the obtained elastic strains to stresses [14] requires the Young's modulus E and Poisson's ratio n, which were assumed to be 102 GPa and 0.34 for nano-crystalline Cu and 338 GPa and 0.36 for nano-crystalline W, respectively [1]. These properties were averaged by following the rule of mixture and considering a material ratio of Cu:W of 1:1, resulting in average elastic properties of / *0/2 = 220 GPa and ̅ *0/2 = 0.35.…”

“…Nano-multilayers allow for the design of materials with unique mechanical, electrical, optical and functional properties by combining the advantages of different materials in a layered structure [1]. Copper and tungsten (Cu/W) multilayers are promising candidates for the thermal management at micro and nano scale, combining the excellent thermal and electrical conductivity of Cu with the low thermal expansion and high mechanical strength of tungsten [2][3][4].…”

Optimizing Fragmentation of Metallic Film for Cracked-Based Strain Sensor

“…Compressive stresses then develop across the width of the film due to Poisson’s ratio effect, which generates shear stress at the metal–polymer interface and causes transverse buckling. − A brittle film exhibits fragmentation and forms channel cracks, , whereas a ductile film may experience large plastic deformation. ,, In the case of supersensitive sensors based on the cracked conductive layer, cracks need to be introduced in a highly conductive layer, typically a layer of copper or gold. , However, such materials are ductile, and the fragmentation of such layers is difficult. To facilitate fragmentation, a multilayer approach is commonly used, in which a ductile layer is coupled with a brittle layer, which dictates the cracking behavior. ,, Cracks initiate in the brittle layer and can then be relaxed through the ductile layer . The mechanical behavior of brittle–ductile bilayer and multilayer systems has been investigated at different scales. ,, Kreiml et al used an Al/Mo bilayer system to demonstrate that the ductile/brittle thickness ratio significantly influences crack morphology and electrical performance.…”

“…To facilitate fragmentation, a multilayer approach is commonly used, in which a ductile layer is coupled with a brittle layer, which dictates the cracking behavior. 18,20,21 Cracks initiate in the brittle layer and can then be relaxed through the ductile layer. 22 The mechanical behavior of brittle−ductile bilayer and multilayer systems has been investigated at different scales.…”