LATTICE AND DEFECT STRUCTURES OF POLYMERIZABLE DIACETYLENE LANGMUIR-BLODGETT-FILMS STUDIED BY SCANNING FORCE MICROSCOPY

The scanning force microscope has been used to study the lattice and d efect structures of multilayers of the unsaturated fatty acid, 12-8 di acetylene (10,12-pentacosadiynoic acid) in ambient conditions. Films w ere prepared by the Langmuir-Blodgett technique on ordinary microscope glass and indium tin oxide coated glass. Lattice structures were dedu ced from the well resolved molecular images and, before polymerization , were found to be nearly centered rectangular with lattice parameters (0.88+/-0.06) nm and (0.51+/-0.04) nm. After exposing to ultraviolet radiation for polymerization the lattice structure changed to an obliq ue lattice with lattice parameters (0.466+/-0.008) nm and (0.55+/-0.01 ) nm. Molecular level defects such as dislocations and grain boundarie s were resolved in these films very clearly. Observation of these kind s of defects implies that it is possible to reliably image the real su rface molecules under ambient conditions. Polymerization was found to take place in one of the lattice directions and the modulation perpend icular to that direction was more pronounced than along the polymer ba ckbone. (C) 1995 American Vacuum Society.