FIGURE 6-6 A: This AFM image of a test pattern appears to have dark right edges. B: The artifact can be easily seen in the line profile. Although this artifact could be explained by a large angle between the probe and surface, the probe surface angle cannot be this large. Scan size: 91µm X 91µm.

6.1.4 Repeating Strange Patterns in an Image

If the features on a surface are much smaller than the probe, it is possible to see large numbers of repeating patterns in an image. The patterns will often appear as triangles, especially if silicon probes are used for imaging. Example: Images of colloidal gold particles reflect the shape of the tip rather than their own geometry. Compare the SEM images of tips and related AFM images of spheres in the Figure 6-7.

FIGURE 6-7 The AFM images at the right, B (5 nm in diameter) and D (28 nm in diameter), are of nanospheres that are supposed to be perfect spheres. At the right, A and C, are scanning electron microscope images of the AFM probes used for getting the images of the spheres. Because the chipped probes are much larger than the spheres, the AFM images reflect the probe's geometry. The scan size is 700nm x 700nm.