I got some single-walled carbon nanotubes (SWNT) the other day. They're 5 nm in diameter and are functionalized with a detergent, which coats the SWNTs so that they can be dispersed in water. Here's a 492 X 492 nm image I took with the STM after placing a drop of SWNT solution on HOPG and allowing it dry:
Those lines in the top-right have a ~5 nm pitch, so I suspect it's a bundle of SWNTs. The HOPG surface looks really "noisy", probably due to detergent left on the surface. I definitely crashed the tip at least once, so that might have something to do with it! Looks like the tip changes in some way about a third of the way down the image. I'll try baking off the detergent to see if it changes anything, and try a few more scans to see if I can find some individual SWNTS.