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How to achieve higher contact force in force measurements?

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glopo posted on Tue, Feb 26 2013 12:04 PM

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Hello,

I'm using Multimode IIIa AFM. I'm trying to do some force measurements with polymers layers. Cantilever I usually use have spring constant around 100 pN/nm.

The maximum contact force I can achieve with these probes are around 4 nN (deflection around 40 nm), and the breakthrough events through the layers I'm studying in generally occur at higher forces. 

Is there any way I can achieve higher contact force? I was playing with deflection setpoint but it does not give much higher values of force (or I lose the contact region of the curve).

When working on other AFM instruments (home made AFM), with these cantilevers I was able to achieve much higher contact forces. Is there something I'm doing wrong?

Thanks,

Glopo

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Answered (Not Verified) Ang Li replied on Wed, Feb 27 2013 3:23 AM
Suggested by 王硕

The trigger threshold controls the force and I am not sure whether your 'deflection setpoint' refers to the trigger or to the imaging setpoint. Anyway, if you lose contact region of the curve when you have larger threshold, just increase the ramp size or use step motor to move up a bit to get it back. Another simple way is to use a stiffer cantilever.

Ang Li

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is this kind of Digital Force Gauge precise enough to measure that little force. What's your experience with it?

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