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Peak force QNM, Probe calibration

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BenSD posted on Sun, Feb 26 2012 3:17 PM

Hello,

I just acquired the Peak force QNM package on a Bioscope catalyst and I would like to know what would be the best way to calibrate stiff probe (TAP525)?

What I did so far is using the sapphire surface to calibrate the deflexion sensitivity and then the thermal tuning and the sader methods for the spring constant, then I used the rough Ti surface for tip radius determination. However when I checked the calibration with calibated surface (2.7GPa), I am usually way off...

Does anybody can tell me what I am doing wrong, and if there is better way to do the calibration for stiff probes?

 

Thank you,

Benoit.

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Ang Li replied on Sun, Feb 26 2012 8:06 PM

Hi, Benoit,

Your procedure sounds on the right track, you may send me the deflection calibration force curve, probe calibration file and the QNM file on the calibrated sample, you may just have overlooked some little issues. My contact is ang.li@bruker-nano.com

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Suggested by Bede Pittenger

Those probes are a bit stiff for the thermal technique.  I would suggest the "Sader Method" as an alternate option that might give more accurate results: http://www.ampc.ms.unimelb.edu.au/afm/calibration.html

This document describes the options for spring constant calibration and the advantages and disadvantages of each: AN094-RevA0-Practical_Advice_on_the_Determination_of_Cantilever_Spring_Constants-AppNote.pdf

 

--Bede

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BenSD replied on Mon, Feb 27 2012 1:08 PM

Thank you Ang Li, I didn't save all the calibration step, so let me do it again and I will send you the files.

 

Benoit.

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BenSD replied on Mon, Feb 27 2012 1:11 PM

Hi Bede,

Actually it is what I did.

I did thermal tuning and enter the Q parameter and the frequency I got from the thermal tuning into the "Sader method" website. For the width and length I took the nominal value provided by Bruker.

Could you tell me if I did it the right way?

Thanks,

Benoit.

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That is how I would do it.  Please be sure to read the app note and the Sader paper for more details.

If your purpose for finding the spring constant is to calibrate PFQNM, you may want to use the "Relative method".  We have found it works better (especially for stiff probes), but you do need a reference material with known modulus.  Imaging the reference material allows you to find the K/sqrt(R) ratio quickly and "relatively" accurately.

--Bede

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