The Nanoscale World

PFT and Cycle Averaging

PFT and Cycle Averaging
posted by Stephen Minne
Thu, May 3 2012

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The cycle averaging of Tapping limits performance because 1) the high resolution tip-sample interaction only occurs when the tip is close to the sample, and this is a fraction of the cycle, and 2) at low imaging forces, the effects of long range forces dominate the cycle. (This is also why atomic Tapping images are done in fluid. . . eliminate the long range capillary force.)

A better approach is to use PeakForce Tapping because it does *not* measure the average force over the entire cycle, but only the desired high resolution repulsive interaction when the tip is closest to the sample. We will have a webinar shortly that describes this in detail, but you can see start to see this in the slides at the link.

There is a lot on the graphic, but the key take away is the force vs time trace on the bottom right. Tapping averages all of the attractive forces (blue) and repulsive forces (red); making it hard to tease out the desired high resolution interaction (red). PeakForce Tapping, lets you measure the peak repulsive force (red) independently, and it is why we can get atomic resolution any of our systems, without any limitations or compromise in terms of sample size, AFM flexibility (modes & accessories), or costly/rare probes.

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