AFM nanoindentation-based mechanical investigation of 3D confinement effects on nanoarchitectonic arrays of Ag nanodisks

Ag nanostructures have been widely used in the development of emergent micro electro-mechanical systems (MEMS) and nano electro-mechanical systems (NEMS). Dimensional confinement effects on their mechanical properties are a key issue in the field of MEMS/NEMS for understanding their mechanical performances and potential lifespans. In this work, we report a systematic study of 3D 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 radii (r) between 125 and 900 nm have been studied. Mechanical properties have been studied by atomic force microscopy (AFM)-assisted nanoindentation. The results showed a strong influence of substrate effects on the mechanical response of the nanodisks, generally being dominant at the considered scales. Lateral confinement effects have been observed for low indentation depths (<0.1 t), at which the substrate effects become smaller. Confinement effects depend more on relative size effects (r/t ratios) than on absolute length scales. The nanodisks showed greater susceptibility to plastic deformation (lower mechanical resistance) as r decreased; this became clearly appreciable when r was comparable to 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 mechanical behavior of solids.