X-ray photoelectron spectra were measured for a single cadmium arachidate (cadmium eicosonate) monolayer bonded via the carboxylate group to various metal and metal oxide surfaces. Two well-defined peaks were observed in the C ls spectra of these systems: an intense peak due to ionizations from the CH2 and CH3 carbons and a less intense peak due to ionizations from the CO2- carbon. Differences between the binding energies of these two carbon peaks were found to vary with the surface to which arachidate was bonded and these differences are interpreted as arising from differences in the charge transfer between the various surfaces and the arachidate. In addition the carbon initially present on the metal/metal oxide surfaces and the effect of submerging the surfaces in the monolayer tank were studied and it was found that this source of carbon had a negligible effect on the positions of the arachidate carbon peaks. © 1982 American Chemical Society.