ECOF 6. European Conference on Organised Films. Sheffield UK, 1996.
INVESTIGATION OF TRANSITION LAYER IN LANGMUIR-BLODGETT FILMS
P.P. Karageorgiev, V.V. Karageorgieva, V.V. Luchinin, A.Z Kazak-Kazakevich, A.N. Dunaev
Microtechnology Centre of St.-Petersburg Electrotechnical State University, Professor Popov sir. 5, St.-Petersburg, 197376, Russia
Studies by Reflection High-Energy Electron Diffraction, Atomic-Force Microscopy, and Low-Angle X-ray Diffraction techniques have been conducted into Langmuir-Blodgett Film (LBF) structures of insoluble amphiphilic substances (e.g. stearic acid) in relation to substrate materials and surface morphology, the subphase ionic composition, and the state of the subphase surface monolayer. The evolution of the film structure has been investigated step-by-step with increasing number (from 1 to 4) of the applied monolayers. The lattice distortion parameters, namely, the fluctuating lattice constant and inclination of molecules, as well as the average size of crystallites have been determined both in the plane of the layer and normally to the substrate, for which purpose either a two-dimensional or a one-dimensional paracrystall model was used in the analysis of diffraction pattern intensity distributions. A correlation has been established between the degree of the film structure distortion and the substrate surface properties such as the morphology and the surface centers kind and force. A model is suggested for interaction between the substrate and an overlying amphiphilic monolayer. This interaction results at the initial stage of the approach from overlapping diffused areas of the double electrical layers which are induced by distributed surface charges of the substrate and of the monolayer within the subphase subsurface volume. As the surface is approached, the local interaction of amphiphilic molecules with surface centers becomes the determining factor in the monolayer structurization. A proposed criterion that is based on a definite relationship between surface potentials of the substrate and the monolayer provides a means for both predictable and controllable degree of structural disorder in LBF. The monolayer self-structurization tends to be enhanced under UV irradiation of the substrate. This effect has been found to be selective components in addition, we have discovered that either aluminum or antimony, being incorporated into searic acid monolayers, can bring about a transformation of the short-range molecular environment in the film plane causing a change in the local packing of molecules. The suggested theoretical concepts and approaches can be applicable to a wide range of insoluble amphiphilic LB films.
P.P. Karageorgiev, V.V. Karageorgieva, V.V. Luchinin, A.Z Kazak-Kazakevich, A.N. Dunaev. Investigation of transition layer in Langmuir-Blodgett films // European Conference on Organised Films ECOF 6. Sheffield UK, 1996, p. 2.13