Electron Microscopy of Organic Thin Films

[摘要] Thin films of organic materials are increasingly being used for technological applications. In this study two methods of thin film production, Physical Vapour Deposition (PVD) and Solution Casting on a water surface, have been used to prepare thin films of organic materials for investigation by Transmission Electron Microscopy. The polycyclic aromatic compounds perylene and quaterrylene were evaporated under high vacuum onto the (001) face of a freshly cleaved crystal of KCl. Substrate temperature was shown to play a important role in determining the crystallinity and morphology of the thin film produced. An optimum substrate temperature was found at which deposited crystals were smooth, formed large domains and did not undergo re-evaporation from the substrate. Lattice images were obtained for the quaterrylene and some image processing was attempted. The second class of compounds studied were a range of octasubstituted phthalocyanines that were synthesised. These compounds are potential one dimensional conductors since they stack in a "face to face" manner allowing good n-orbital overlap. The compounds prepared were all based on the octa-dodecyloxy-phthalocyanine unit and were the metal free, copper, silicon-dihydroxy and polysiloxane derivatives. Films of these compounds could be prepared by allowing a chloroform solution of these compound to evaporate on a water surface. Information was obtained by electron diffraction and by lattice imaging. The most common packing arrangement was for a stack of molecules to lie parallel to the water surface. The molecules in the stack could be either tilted or perpendicular to the stack. Only the copper derivative showed any evidence of lying flat on the water surface. The unusual packing of these molecules was explained in terms of the strong hydrophobic interaction between the paraffin side chains and the water surface.

[发布机构] University:University of Glasgow

[关键词] Analytical chemistry