[en] A modified Langmuir-Blodgett (LB) technique for the preparation of small size radioactive sources as monomolecular layers is presented. The method is based on the chemi-sorption of radionuclide ions from a drop of a water solution onto a stearic acid monomolecular layer attached to a metallic backing. A chemical yield as much as 90% was achieved for some rare earth elements studied. Optimalization of the adsorption conditions was performed. Low energy electron spectra (E_e<10 keV) measured with a 6.5 eV resolution using ¹⁶⁹Yb sources prepared by the new method were found to be negligibly influenced by electron energy loss processes. Energy losses of 6.1, 6.3 and 10.6 keV electrons in the LB films consisting of 1, 3 and 5 pure stearic acid monolayers and those labelled with inactive ytterbium were studied by means of an electrostatic spectrometer adjusted to a 6.5 eV instrumental resolution. Probabilities and energy loss values of the individual inelastic scatterings were determined. Accomplished Monte Carlo simulations for electron transport of studied electrons in the LB matter are compared with the measurements. (orig.)