Above : A 12nm x 12 nm STM image of 12-bromododecanoic acid in phenyloctane on graphite. One molecular length is indicated by a black bar. Numbers 1-11 (upper right corner) refer to the positions of 11 hydrogens on the 11 methylene carbons of a single molecule, and Br refers to the position of the Br atom. The dark blotches are multiple, side by side -COOH-HOOC- dimer groups. Because Br atoms attract each other in the self-assembled layer, they appear as bright Br-Br doublets.