STRUCTURAL-CHANGES BEFORE AND DURING DESORPTION OF LANGMUIR-BLODGETT-FILMS

Langmuir-Blodgett (LB) films of cadmium arachidate are studied by optical reflection, optical microscopy, and small-angle X-ray diffraction with special emphasis on the temperature dependence between 100 and 150-degrees-C. It is shown that at about 110-degrees-C a transition into a state with uniform thickness but with loss of discrete layer structure occurs. The thickness of this film decreases when the temperature is increased and then detracts in a typical dewetting process. Droplets are later formed, leading to strong light scattering. A special benefit of this study results from the refined methodology. Bragg diffraction as well as Kiessig fringes could be well resolved, and Nomarsky microscopic observations were quantified. This enabled correlation between optical images and X-ray scattering data.