Best wedge method calibration grating?
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Hi all,
I am interested in the wedge calibration method.
We are using a UHV-FFM with a scanrange of 3x3mu m.
Varenberg (M. Varenberg, I. Etsion & G. Halperin. "An improved wedge calibration method for lateral force in atomic force microscopy". Rev. Sci. Instrum. 74, 3362-7 (2003)) recommends the TGF11 calibration grid. It is rather big for our small scan-ranges but could in principle be used.
What test grids do you recommend?
Thanks for help in advance,
Christian -
Hi Christian,
We had good results using the TGF11 in a straightforward way, as described in your paper, so you are on the right track. There is some software on this website that will help you do that work. The problems we hit along the way were 1) making sure the TGF11 surface was clean and smooth - oxygen plasma was the way to go for this (most other cleaning methods only made it dirtier!); 2) we had to choose colloidal spheres small enough to fit in there, so make sure yours does too if you're using one; 3) check the epsilon value of your cantilever/tip (as described in the paper) before you go through the work. Only cantilevers with epsilon << 1 can give physically meaningful results, otherwise in-plane bending is convoluted in with the twisting and the results don't make sense. Again this depends on your tip, it was an issue with our colloidal tips.<br />Good luck,
Tolga
LSST, ETH Zurich -
Christian - Tolga makes a lot of good points. I guess with your UHV FFM it is not easy to coarse-position the tip over a desired region. Essentially you'd like to get a flat and a sloped region in one image. Aiming for the flat valley is the best, since it's narrower, so you can get the flat valley and maybe both positive and negative slopes in one image.
Unfortunately, WiTec no longer makes the SrTiO3 sample, which was nice for small scans (and regular tips, as opposed to colloidal probe tips).
You might also try the TGG01, which has a smaller period (3 um, vs. 10 um for the TGF11). Let us know how it works out!