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Hi everyone, I have been doing some reading about obtaining atomic resolution with AFM and there is a main issue that I don't understand.
Do you need a single tip atom to interact with a single atom from the sample to obtain atomic resolution?
If a tip radius is larger than 20 nm is it possible to have single atom interaction or atomic resolution?
If anyone can explain what is believed to happen between the tip and substrate (either in contact or noncontact mode) or knows about a reference I will be very thankfull
Cheers,
Luis
Hi Luis,
The question is not necessarily how big the tip is but what size of the tip interacts with the surface. E.g. STM tips are often not very sharp but produce nevertheless stunning atomic resolution images on reasonably flat surfaces. The reason is that the exponential distance dependence makes only the front atom interact with the surface.
The distance dependence in AFM is less than STM so care has to be taken in selecting the imaging mode and environement as this will determine how much of the tip interacts with the surface and thus contributes to the resulting image. In contact mode the tip typically deforms the surface quite a bit thus making the interaction area quite large. The resulting data are therefore lattice resolution without the possibility to see single atom defects. PeakForce Tapping allows you to select to work on the attractive side of the force curve and thus avoid having a large area of the tip interact with the surface. This in turn can yield the images with true atomic resolution that Bruker has shown.
Stefan
Thanks Stefan! You answer helped me a lot, especially the concept that you need to work on the attractive side of the force curve!
Always try to work at the smallest forces possible for atomic resolution. Your biggest enemy are meniscus forces (which are of course not present when sample and tip are immersed in fluid). Having the ability for precise force control is essential for that.