Elastic modulus and fracture strength evaluation on the nanoscale by scanning force microscope experiments.

ABSTRACT

This work first reviews the capability of scanning force microscopy (SFM) to perform experiments with forces in a wide range, from low non-contact forces to high contact forces which induce mechanical deformations in the substrate. In analogy to fracture strength evaluation, as established in materials science, SFM is used to exert forces on pillars with nanometer dimensions while the cantilever deformations are monitored quantitatively. Hence, it is possible to bend the pillars until the threshold for triggering fracture is reached, and to determine the mechanical properties at the different stages of this process. Using this novel approach, in combination with 'state of the art' nanofabrication to produce nanopillar arrays on silicon and silicon dioxide substrates, a number of experiments are performed. Furthermore, quantitative measurements of the fracture strength of Si and of the SiO2/Si interface and E-modulus are presented. To analyze the experimental data obtained in the different experimental procedures and modes, finite element method calculations were used. The methods introduced herein provide a versatile toolbox for addressing a wide range of scientific problems and for applications in materials science and technology.