Effects of 3-D Confinement on the Mechanical Behavior of Ag Nanodisks: Novel Insights into Nanomaterials Mechanics

Abstract

Ag nanostructures have been widely used for the development of emergent Micro Electro-Mechanical Systems (MEMS) and Nano Electro-Mechanical Systems (NEMS). The dimensional confinement effects on the mechanical properties are a key issue in the MEMS/NEMS area for understanding their mechanical performance and potential lifespan. In this work, we report a systematic study about the 3-D confinement effects on the mechanical resistance of Ag nanodisks fabricated by Interference Laser Lithography (ILL). Nanodisks with thicknesses (t) between 20 and 150 [nm], and radiuses (r) between 125 and 900[nm], were studied. Mechanical properties were studied by Atomic Force Microscopy (AFM)-assisted nanoindentation. Results showed a strong influence of substrate effects on the nanodisks mechanical response, being generally dominant at the considered scales. Lateral confinement effects were observed for low indentations depths (<0.1 t), where the substrate effects become smaller. Confinement effects depended more on relative size effects (r/t ratios) than absolute length scales. The nanodisks presented more susceptibility to plastic deformation (lower mechanical resistance) as r decreased; being clearly appreciable when r becomes comparable with t. Complementary finite element analysis showed similar tendencies, which could be explained considering pure dimensional confinement effects. This study shows the potential capabilities of modern AFM instruments for understanding confinement effects on the solids’ mechanical behavior.