There has been significant interest in quantifying the functional and nanomechanical response of materials.  Virtually all of the Atomic Force Microscopy (AFM) measurement modes use a microcantilever.  The cantilever shape as it interacts with the sample determines both the mechanical parameters (stiffness for example) and the optical detector sensitivity. By using the encoded and motorized optical beam controls on a commercial microscope, schematically indicated in Figure 1(a), we have been able to directly measure the extended shape of the cantilever � in-situ � as it interacts with various samples and in a variety of measurement modes. In many cases of interest, the response of a cantilever does not behave as a simple, single-mode harmonic oscillator.To elucidate the effects of local and long-ranged forces on AFM measurements, the response of the cantilever as a function of both frequency and optical beam spot position has been measured in-situ while the cantilever is directly probing the sample.  In one example shown here, piezoresponse force microscopy (PFM) is performed on a periodically-poled Lithium Niobate sample. A PFM spectrogram of the cantilever amplitude and phase was taken on this sample is shown in Figures 1(b) and(c), respectively. One interesting results is that the crossover between the dc and first contact mode is measurable, and therefore affects interpretation of PFM measurements at surprisingly low frequencies. Similar measurements have been made with the cantilever interacting with samples in other modes, including force curves, tapping and bimodal/Dual AC modes and will be presented.

In situ cantilever shape profiling: Implications for quantitative functional and nanomechanical measurements

244th National Meeting (2012)

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