Molecular Positional Order in Langmuir-Blodgett Films by Atomic Force Microscopy

Science  05 Feb 1993:
Vol. 259, Issue 5096, pp. 798-801
DOI: 10.1126/science.259.5096.798


Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules.