Localized surface elasticity measurements using an atomic force microscope

Abstract

Magnetic recording, microelectro mechanical systems, and other microelectronics industries use ultrathin continuous films as well as composite films. The motivation of this research was to identify and map differences in the stiffness or elasticity of these ultrathin films at the very near surface (up to a few nm) by using the force modulation technique. We have shown that this technique amplitudes on samples can yield quantitative elasticity data on samples with an elastic modulus up to a few tens of GPa. This technique provides an alternative to current elasticity measurements that require forces higher than 1 μN, and which can only make single point measurements. With this technique it is possible to make quantitative measurements with loads as low as a few tenths of a μN. By choosing tips that match the stiffness of the sample, the depth of the indentation during the elasticity measurement is kept small, thus eliminating significant plastic deformation of samples of any hardness and any stiffness. The technique has been applied to quantitatively measure the elasticity of polytetrafluoroethylene and to qualitatively map magnetic tape samples to reveal sharp variations in the surface elasticity due to the composite nature of the polymer matrix with magnetic and abrasive particles.