The question is rather self-obvious. I suspect this should be quite feasible, but any tips are more than welcome, such as scan rates, amplitude setpoints, scan sizes, etc. Might I also note that I will work close to RT temperatures, in aqueous buffered solutions.
My suggestions are:
1. Try working at small-ish amplitudes (0.5 N/m)
3. I find I get better results with relatively soft setpoints (0.7-0.9)
4. High scan rates tend to work better and minimize drift (5-15 Hz) especially for small size scans. The main reason for drift at that scale (assuming you have a close loop) would be thermal fluctuations of the buffer so temperature control helps if available.
5. Your buffer will be a problem. Salt alone is fine, but Tris or phosphate tend to create a 1nm thick layer on mica. You can usually scratch it off though, but the image looks messy.
Hello,
I agree with the answer above by Kislon. I would also say, try small cantilevers and work open or hybrid loop if possible and if the AFM you use allows. Also patience and play a bit with the parameters because sometimes to get the highest resolution depends on the tip which you don't have much control over and therefore the best resolution will dependent on the operational parameters, i.e. bets operational parameters are tip dependent that's why each time you need to vary parameters a bit to get best resolution.
Good luck
Although I'm really not an expert in tapping mode in liquid I fully agree with Kislon and Sergio. I guess high scan rates are cruicial. Too soft cantilevers will surly be a problem. You should also consider other types of excitation than mechanical. You will suffer from hydrodynamic resonaces. Here laser photothermal excitation is known to work, but magnetic excitation should work as well (I guess even with commercial MFM cantilevers).
I suspect that you've better avoid the areas probably dissolving (see e.g.: http://www.sciencemag.org/content/285/5429/874.abstract) and scan between... I also agree with Dr. Voitchovsky to avoid buffers with salts precipitating...
I fully agree with the previous answers on how to image the surface lattice of mica by tapping mode AFM. Alternatively you may consider to friction force microscopy. In this case scanning with a soft cantilever (k ~ 0.1 N/m) perpendicularly to the cantilever axis and at low forces in the order of 1 nN and less should allow for the observation of atomic stick-slip in the lateral deflection signal. In that case scanning with an open loop and high scan rates will be helpful.
I have not tested atomic resolution with tapping mode on the Bruker system. But I mange to get atomic resolution with a MultiMode III in water on mica and on sodium montmorillonite for some years ago.
http://www.skb.se/upload/publications/pdf/TR-10-27.pdf
The lattice resolved images on page 25 of your publication were obtained in contact mode and not tapping mode.
Thanks for sharing your work though.
Excellent, many thanks for all your constructive feedback. It is highly appreciated !
Hi Mike,
Seeing lattices is not equal to "true" atomic resolution—mostly lattices are friction-induced artifacts, particularly for contact mode imaging. High (subnanometer) resolution tapping mode images were very rarely reported. You may having a look at my Surf. Sci. Rep. review on this topic. It can be downloaded from my RG homepage.
Best,
Yang
Kislon and Sergio are right on everything.... with a Cypher and the probes AC55TS, it is actually pretty easy in tapping with small oscillation amplitudes at least to get the lattice. Try to follow their protocols.
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