ATOMIC-FORCE MICROSCOPY OF INSTABILITIES AND REORGANIZATION OF LANGMUIR-BLODGETT-FILMS

The atomic force microscope was used to show that Langmuir-Blodgett fi lms are unstable to reorganization via a folding mechanism by which un iformly thick films spontaneously form holes and multilayer steps. The se bilayer step defects originate at isolated sites and quickly spread to covet the entire film. The defects retain the sixfold symmetry of the underlying molecular lattice; after sufficient time, straight edge s begin to form and the entire film is comprised of high islands with straight edges aligned with sixfold symmetry. The kinetics of the reor ganization depend strongly on the chain length of the fatty acid used and the nature of the substrate. The results suggest that the reorgani zation is driven by an interconversion of strained, asymmetric monolay ers to unstrained, centrosymmetric bilayers.