Probing the mechanical properties of nano-sized objects by a combined in-situ AFM and u-XRD technique

The investigation of semiconductor nanostructures is widely regarded to be one of the most important issues concerning the development of new technologies on the nanometer scale. Although the elastic properties of bulk materials and thin films are well known, it is expected that the mechanical behaviour is altered as the size of the material is reduced to the nanometer scale in 2 or 3 dimensions. To this end, we combined an in-situ atomic force microscope (AFM) employing a tuning fork as a force sensor and X-ray diffraction with a microfocused beam (m-XRD) to quantify the elastic response in nano-objects during the application of a well controlled uniaxial pressure (see fig. 1a). In first conceptual experiments, SiGe islands grown on Si(001) were investigated. From changes in the diffraction pattern during pressure application observed close to the Si (004) Bragg peak, the corresponding variations in the object lattice parameter were derived and could be correlated to shifts of the resonance frequency of the AFM tuning fork (see fig. 1b). This correlation rendered it possible to infer the Young Modulus of an individual nanoobject. In summary, this method paves the way to a whole range of novel experiments on the nanoscale.

Figure 1. Setup of the in-situ AFM. The microfocused X-ray beam (yellow) illuminates the sample residing underneath the AFM-tip (red) which is used to apply a pressure. The diffraction pattern is recorded using a 2D array detector.	Figure 1b: A clear correlation is found between the shift of the tuning fork resonance frequency fres and the lattice parameter change aSiGe as a function of the tip displacement Δz, which is a measure of the applied force

Authors: T. Scheler1, T. H. Metzger1, T. Cornelius1, R. Magalhães-Paniago1, M. Rodrigues1, F. Comin1, J. Chevrier1,2
1 ESRF ID01, 2 Institut Néel  CNRS-UJF

Ref. Appl. Phys. Lett. 94, 023109 (2009)