HREELS-STUDIES OF SELECTIVELY DEUTERATED CADMIUM-STEARATE LANGMUIR-BLODGETT-FILMS

Monolayers of octadecanoic-18,18,18-d3 acid prepared by the Langmuir-Blodgett (LB) technique were used as model systems for studying the interaction mechanisms between slow electrons and organic thin films in high-resolution electron-energy-loss spectroscopy (HREELS). Due to their amphiphilic character these molecules are oriented with their deuterated methyl-group towards the air and with their carboxylate group towards the substrate. From the intensity ratio between the C-D- and C-H-stretching vibrations in HREEL spectra we derive a value the information depth in the order of three C-units of the aliphatic chain at a primary energy of 5 eV. The strong dependence of this intensity ratio upon the primary energy of the electrons between 2 and 7 eV is mainly attributed to a varying information depth. The energy dependence of the cross sections and the underlying interaction mechanisms are also discussed. © 1990.