Emergence of film-thickness- and grain-size-dependent elastic properties in nanocrystalline thin films

Grain Size Dependence of Elastic Moduli in Nanocrystalline Tungsten

“…In such a rule of mixture model, the in-grain regions present a Young's modulus similar to the bulk material while the intercrystalline Journal of Nanomaterials 5 (IC) regions present a smaller one. This was, for instance, confirmed by the molecular dynamics simulations performed recently by Lian et al on bulk nanocrystalline nickel [31].…”

Determining Mechanical Properties at the Micron Scale Using Microfabricated Freestanding Structures

“…Much work has been performed to determine the effect of film thickness and grain size on the elastic modulus of thin films [12,[55][56][57][58][59][60]. Lower modulus due to decreased film thickness is most commonly attributed to the increased volume percentage of softer GBs to the overall makeup of the film [55].…”

“…Lower modulus due to decreased film thickness is most commonly attributed to the increased volume percentage of softer GBs to the overall makeup of the film [55]. The effects of free surfaces present a higher number of compliant grains and surface atoms with respect to the total volume of very thin films and has been shown via MD to have a significant influence on the elastic modulus of thin films [60]. While there are a host of studies experimentally examining the links between microstructure and mechanical behavior of nickel films [61][62][63][64][65][66] The volume percentage of grain boundary material has been described elsewhere [55] and is represented by:…”

“…material for all grain boundary thicknesses. Molecular dynamics simulations have recently suggested the modulus of nickel grain boundary material, E gb , is around 100GPa [60]. We will use this value in our analyses and assume the intergranular material, E ig , to have a modulus of 205 GPa.…”

“…• C anneal condition than the thicker films with the same approximate grain sizes. Recent studies have suggested reduction in modulus for thin films may be linked to surface effects lowering the modulus of surface atoms or variations in surface stress [25,27,59,60,67]. The pronounced reduction of modulus suggests thickness plays a significant role in the modulus decrease, however, the absence of any reduction in modulus for the 300 • C case seems to contradict this idea.…”