The Nanoscale World

very stiff cantilevers/diamond tips for QNM

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dalia posted on Thu, Feb 9 2012 8:21 PM


I would like to try QNM on some very stiff materials (100GPa-200GPa) most to look for material contrast, not necessarily quantitative moduli, and it was recommended that I use the nanoindentation probes (stainless steel cantilever, diamond tip) since compliance of the Si cantilevers is not appropriate for these materials. Some questions on this:

1) I thought we needed Al coated cantilevers for QNM?  Would the stainless steel provide sufficient signal?

2) THese are really stiff, so I"m assuming any kind of spring constant calibration (based on thermal tunes, what comes available) is not possible, so we will not be able to fully calibrate the system.

3) Are there other manufacturers/tips that could be recommended? i did see sciences nadiaprobes - all diamond cantilever and probe with an Al coating. Would these be appropriate?  Are there others?



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Top 25 Contributor
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Bruker Employee
Suggested by Bede Pittenger

Hi Dalia,

I can answer some of your questions.

1 - The stainless steel cantilevers have a small "mirror" mounted to the backside of the cantilever near the free end.  For this reason, you will get a good reflection and this would serve the same function as the Al coating on the other probes. You should be able to see this mirror optically.

2 - The spring constant for these cantilevers is calibrated at the factory, so you should have received a calibration certificate with the probe.  If not, let me know and we can track down that information.  They are not calibrated by the thermal tune method, but use another method due to their stiffness.

You will still need to calibrate deflection sensitivity with the sapphire sample, but you can skip the spring constant determination step.  If you are running QNM qualitatively, I would calibrate deflection sensitivity, put in your sample and give it a try. 

I hope this helps. 



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Ang Li replied on Mon, Feb 13 2012 1:28 AM

Hi, John,

Can I just manually update the deflection sens with the contact sens quoted in the spec and thus skip calibrating it? thanks!


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Top 25 Contributor
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Bruker Employee

Hi Ang

I would recommend calibrating the deflection senstivity on the sapphire sample if you want it to be accurate.  Deflection senstivity will change with your laser position on the back of the cantilever, so every time you adjust the laser, you will need to calibrate this if you want to measure the correct cantilever deflection in nanometers on the photodetector.. 

If you want a general "ball-park" number, you could enter the deflection sensitivity number from the calibration sheet manuallly as you suggest, and it will be close.  For some applications, such as running QNM qualitatively, this is fine.  However, calibrating deflection senstivity is a quick step, and this will calibrate the adhesion channel (along with entering the spring constant), for instance, so I think it is worth it.  

Hope this helps.



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