Caliber Point Spectroscopy

Harman posted on Thu, Sep 23 2010 12:57 PM

rated by 0 users

Hi,

I'm trying to perform force-distance analysis using the TESP/TESPD probes on the Veeco Caliber SPM. There are two issues I'm facing, that I could really use some help with:

1. My primary samples are unfilled PTFE and unfilled PEEK. Doing indents on PTFE with a new TESP tip, I am able to get hardness values of around 50MPa (with some spatial scatter). However, I notice that if I indent PEEK, and return to indenting PTFE, my hardness values jump by at least a 100MPa (PEEK gives me hardness of over 1 GPa). Would it be reasonable to assume that my tip geometry changes (more specifically, the tip get broken off or blunted) during the indent of a relatively hard PEEK, which is why I'm not able to go back to the same hardness value on PTFE (I'm using physical dimensions of the tip to get my area function)?

2. Related to the problem above, does the Caliber have an in-built lateral motion compensation for the indentation tip rotation?

3. I've noticed that during the approach/retraction of the piezo, before it comes into contact with the surface, my deflection-piezo position curve isn't flat/horizontal. It seems to be slightly (damped) sinusoidal, and the amplitude/period changes from time to time. I've tried swapping different samples (metallic/polymeric) assuming this might be due to electrostatic charge, and have also tried using different cantilevers, change indent speeds- but this seems to show up regardless. This is a concern for me because I'm interested in doing really shallow indents, for which I need really low threshold voltages- and often, the order of this out-of-contact variation is of the order of magnitude of my threshold voltage, and this also makes it difficult to judge where exactly my snap-to-contact occurs. This is a jpeg for the curves I get:

http://i933.photobucket.com/albums/ad175/rokmeamadeus/inde.jpg

I'd really appreciate any help on these.

Thanks,

Harman.