A high resolution electron energy loss spectroscopy study of the Sb/GaAs(110) and Sb/InP(110) systems grown at room temperature is presented. A model calculation is adopted to fit the intensity and energy position data of the Fuchs Kliewer phonon of GaAs, on varying the Sb coverage. The results shed light on the importance of the effects induced by the overlayer thickness. New data on the Sb/InP(110) interface shows that antimony grows as a non-crystalline structure at least up to a coverage of 20 ML. A highly ordered epitaxial monolayer is obtained after appropriate thermal treatment.