Tip Qualification - Searching for a "best practice" procedure

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Polis Tyrol Posted: Thu, Sep 5 2013 3:42 AM

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Dear community,

I am trying to improve the way I qualify my AFM tips. So far I am not completely sure if I'm do everything correctly, especially as both the NanoScope Analysis software (version 1.40 R3Sr4) and the help function let the user chose many values I am not sure what they do. I had to see that already quite small changes in those values have a strong influence on the results. The Peak-Force QNM manual gives relatively detailed recommendations on how to measure and evaluate, but I also found some contradicting recommendations. Unfortunately, I could not find any Application Note on that topic.

I work on a MultiMode 8, primarily using RTESPA probes in Peak-Force QNM mode and ScanAsyst-Air probes in ScanAsyst mode. Currently I usually image the Titanium roughness sample from Bruker AFM at a Scan Size of 1.5 µm, with an Aspect Ratio of 2, 512 px Scan Size and 0.5 Hz Scan Rate.

For the evaluation I start "Tip Qualification" in the NanoScope Analysis without any preprocessing. I choose Tip Image Size as 200 nm. I normally don't use and Low Pass Filter, but when I do I never use more than 3 iterations. I don't know what the Sigma Mult functions do, so I leave them at their default values of 3.5. Equally, I normally don't change the Cross Section values. The help function recommends to save the tip, to reopen it and to use the Section function to plot a cross-section. The software calculates a radius of curvature then. However, if I do so this, the measured radius is very different from the one I find via the Tip Qualification function (e.g. 25 nm instead of 9 nm), and it depends strongly on the Horizontal Distance (distance of the two lines between which the fit is conducted).

My questions are following:

1. Does that procedure sound reasonable to you? Would you change any of those values?
2. What tip radii are measurable? The ScanAsyst tips should have tip radii of down to 2 nm. Are such small radii actually measurable?
3. There are often only few "peaks in ETD 1", sometimes only one. I guess this is a sign that I shouldn't trust the results. What can I do to icrease the number of peaks used for estimation?
4.  How can I reduce the differences between the tip radii estimated via Tip Qualification and those measured on the saved tip? If they are different, which one is more trustworthy?
5. Is there an Application Note or something comparable available about that topic?

Looking forward to an interesting discussion,
Dietmar

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Polis Tyrol replied on Thu, Sep 19 2013 4:06 AM

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Dear all,

Still an open issue. What I could find out in the meantime is the following:

ad 3. By decreasing "Tip Image Size" the software evaluates more tips. I found that a "Tip Image Size" of about 50 nm was enough for me.

The other questions are still open. Have you got any ideas?

Best regards, Dietmar