AVS 47th International Symposium
    Processing at the Nanoscale/NANO 6 Tuesday Sessions
       Session NS+NANO6+MM-TuM

Paper NS+NANO6+MM-TuM2
Quantitative Imaging of Dynamic Mechanical Properties by Hybrid Nanoindentation

Tuesday, October 3, 2000, 8:40 am, Room 302

Session: Nanomechanics
Presenter: S.A.S. Asif, University of Florida
Authors: S.A.S. Asif, University of Florida
K.J. Wahl, Naval Research Laboratory
R.J. Colton, Naval Research Laboratory
Correspondent: Click to Email
In this paper, we present a novel quantitative stiffness imaging technique and demonstrate its use to directly map the mechanical properties of materials with nm-scale lateral resolution. This is a powerful new approach that can eliminate tedious point-by-point analyses of indentation arrays to obtain quantitative mechanical properties of surfaces. For the experiments, we use a 'hybrid' nanoindenter, coupling depth-sensing nanoindentation with AFM scanning capabilities. AC force modulation electronics have been added, enhancing instrument sensitivity and enabling measurements of time dependent materials properties (e.g. loss modulus and damping coefficient) not readily obtained with DC techniques. Tip-sample interaction stiffness images are acquired by superimposing a small AC force (10's of nN) onto the DC imaging force (1-2 µN), and recording the AC displacement amplitude and phase as the surface is scanned. Combining a dynamic model of the indenter (having known mass, damping coefficient, spring stiffness, resonance frequency and modulation frequency) with the AC response of the tip-surface interaction allows evaluation of complex stiffness maps. We will demonstrate the use of this approach to obtain quantitative loss and storage stiffness images for elastic and viscoelastic surfaces, as well as discuss a method to directly determine loss and storage moduli from the images.