ULTRATHIN METAL-FILMS AND INORGANIC CLUSTERS VIA THERMODESORPTION OF LB FILMS

Langmuir-Blodgett multilayers of cadmium arachidate and ferric stearate were investigated during heating in order to derive information on processes involved in thermodesorption and on the inorganic microstructures left on the substrate after thermodesorption. We studied these processes by X-ray induced photoelectron spectroscopy (XPS), interference enhanced reflection (IeR), Nomarsky microscopy, electron microprobe analysis and in the case of Fe-57-ions by conversion electron Mossbauer spectroscopy (CEMS). Two different mechanisms of desorption were observed. In the case of cadmium arachidate multilayers it is shown that before desorption the film ruptures laterally and then forms droplets. At temperatures between 250-degrees-C and 350-degrees-C the aliphatic molecular part is desorbed and the inorganic material (Cd) remains on the surface. These threedimensional Cd-clusters have a rather uniform lateral distribution and dimension (0.5-2-mu-m) and normal extension larger than 1000 angstrom. The size may be controlled via nucleation and growth kinetics. In contrast to this thermodesorption of the aliphatic chains of ferric stearate multilayers leads to a rather uniform continuous oxidic layer. By means of CEMS it could be shown that during desorption under H-2-atmosphere the iron was reduced (e.g. 40% metallic iron). The degree of oxidation can be controlled via temperature and time of reduction.