Multiple Scales of Artefacts

In this example, a tip roughness sample is imaged with a well worn Si probe. An image was taken in PeakForce mode with 5 nN of peak normal force. At 1 x 1 um the image is quite unremarkable. One might suspect a little probe wear based on the lack of resolution of some of the small grains. That could be a good thing if one were wishing to do some nanomechanical measurements or QNM mapping to get elastic moduli. But there is no obvious self-similarity to the objects, and no obvious companions. In the top left some quite small grains can be resolved on the larger grain. Structures well below 100 nm-- suggesting a good probe. Working out at 10 x 10 um would would anticipate good performance.

Except-- that is farthest from the truth. At the larger scan size there is nothing but self-similarity of the objects images, companions, preferred orientation-- all the signs that scream ARTEFACT.

The artefacts we see-- and don't see-- is a function of the 3D structure of the end of our probe, as well as the nature of the structures we are imaging. Their size and shape relative to the structures that define our probe. Here, a horribly damaged probe had a little tiny point on its end-- and that allowed quite good imaging at very small length scales. Above that, the blunt shape of the tip convoluted every feature into an array of heart- or bird-shaped artefacts.