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Force separation curve of HOPG test sample

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bhaskarchilukuri posted on Tue, Jan 15 2013 12:47 PM

Hello,

We have recently started using peak force-QNM to determine the mechanical properties of certain surfaces. We began with doing the test samples provided to us by Bruker, one of which is HOPG.

We used the RTESPA probe and followed the standard procedure to determine the modulus of elasticity from the Force-separation curve (attached below). 

Questions:

 a) We could not understand why the retrace curve (red colored) is to the right of trace curve (blue colored). Can someone explain what the reason could be?

 b) We did similar experiments with other test samples like polystyrene where the force-separation curves looked normal like most other samples do, where the retrace (red) curve is to the left of the trace (blue) curve. So is this sample dependent or do you think our procedure may be wrong?

c) Also let us know any other samples that you may know from the literature that shows this behavior. 

 

Thank you for your help in advance

--

Bhaskar

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Ang Li replied on Thu, Jan 17 2013 2:31 AM

Hi, Bhaskar,

What system are you using? Could you turn z close loop on so you can collect force curves on height sensor instead of height?

Ang Li

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王硕 replied on Thu, Jan 17 2013 4:36 AM

We perform the elastic mapping in water. However, the retrace curve is below the trace curve on HOPG, but we also find that the retrace curve  is to the right of trace curve on nanobubble. And we do not understand too. 

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