The Nanoscale World

Tip Resonant Frequency and Force Constant

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Top 150 Contributor
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Gronfisk posted on Wed, Nov 10 2010 11:17 AM

Hello,

I'm about to order new tips and wanted to know teh effect of the Tip Resonant Frequency and Force Constant.

The  tips that I have been looking at  have resonance  frequencies between 75  to 300 kHz and force constants between 5 and 40 N/m.

I would primarily use the AFM for tapping mode for topography images, but in the future I hope to perform Kelvin Probe Force Microscopy.

The materials that I would be working with are both organic (polymers, sugars) and inorganic nanoparticles and they are often in mixtures.

Which resonance frequencies and force constants should I be looking for?

Cheers!

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Top 25 Contributor
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Bruker Employee

Hi Gronfisk,

 

Firstly the resonant frequency scales with the square root of the spring constant. The main consideration for resonant frequency and force constant is whether the tip will be used in contact or tapping modes. In contact mode you generally would like a low spring constant to minimise both samples and tip damage. In tapping mode you would generally like a high quality factor which scales with resonant frequency.

Considering your samples, for tapping mode topography a good place to start would be with either TESP(300kHz) or FESP(75kHz) probes. For Kelvin Force Microscopy SCM-PIT(75kHz) are a good choice as they are essentially the same as the FESP but with a conductive coating.

I would recommend downloading the excellent new 2011 Probes and Accessories Guide from our site at:

http://www.brukerafmprobes.com/

This has very useful information in helping researchers select the correct type of probe for a particular application.

 

Ian

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