We present a method to improve accuracy in measurements of nanoscale viscoelastic material properties with contact resonance (CR) AFM methods. Through the use of the two-dimensional hydrodynamic function, we obtain a more precise estimate of the fluid damping experienced by the cantilever-sample system in CR experiments, leading to more accurate values for the tip-sample damping and related material properties. Specifically, we consider the damping and added mass effects generated by both the proximity of the cantilever to the sample surface and the frequency dependence on the hydrodynamic loading of the system. The theoretical correction method is implemented on experimental CR measurements taken on a thin polystyrene film. The corrections are especially important for measurements made with the first flexural mode of vibration and on materials with low tan delta (<0.1).
Citation: Journal of Applied Physics
Pub Type: Journals