Frequency Images

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John Thornton replied on Wed, Jan 30 2013 6:21 AM

rated by 0 users

Verified by Peter Eaton

Hi Pete

The Dimension ICON can adjust the drive frequency of the piezo in the cantilever holder to keep the cantilever oscillating at resonance during the Lift scan.  It does this by using a feedback loop to keep the cantilever phase lag at 90 degrees during the Interleave scan.  So, instead of letting the cantilever resonance frequency shift due to magnetic attraction or repulsion and then recording the phase shift or amplitude change at a constant drive frequency, the system will use the phase as the feedback signal and adjust the driving frequency to keep the phase lag constant.  There are integral and proportional gains in the Interleave channel for adjusting this feedback loop. So, you will end up with an image with the data type "Frequency" and the data scale will be in Hz.  This is not just on the Dimension ICON, but also on other models as well, new and old.   I will use this if I want to get a better idea of how much the cantilever resonance is being shifted by the field, since Hz of resonance shift provides a better idea of what is happening instead of degrees of phase shift, and can be a nice way to conduct sample comparisons with the same probe.  Plus, you have the Interleave gains that you can adjust to help fine tune the image when in this mode.  This can also be used for Electric Force Microscopy.  Generally, you will look for something in the Interleave controls called  "Input Feedback" or "Feedback" where you can select "Frequency" - different versions of software have slightly different ways to turn this on. 

I hope this helps.

John