E-MRS – Symposium C Invited Talk

Roger Proksch, Ph.D

"Multifrequency Atomic Force Microscopy and Functional Materials"

Atomic Force Microscopy (AFM) has proven to be an effective means of accessing topographic information of many materials on the nanoscale.  However, tip-sample interactions are complex and many of the measured quantities in conventional AC AFM are complicated mixtures of several tip-sample interaction parameters.  Simply put, there are more unknowns than there are measurements in conventional AC AFM.  This problem is particularly pressing in active materials where information beyond simple topography is routinely desired.  Recently developed multifrequency methods open up new channels for information transfer and allow the unambiguous determination of model parameters.  Some examples of these new multifrequency methods include bimodal AC AFM where multiple resonant modes of the cantilever probe are simultaneously excited, Dual-Frequency Resonance Tracking (DFRT) where driving with two frequencies near the resonance allow sample stiffness and dissipation as well as other properties to be unambiguously extracted and, finally, Band-Excitation (BE), where the cantilever spectral response is extracted in a band of frequencies.  These new techniques have been used to extract information on a large array of samples.  Some examples include extracting high spatial resolution mechanical properties on soft polymer and biological samples, piezo and ferro-electric samples properties and magnetic systems.