BeTe(1 0 0) surfaces and their subsequent overgrowth by extremely thin CdSe-layers with a thickness up to 5 monolayers (ML) are studied by LEED and vibrational Raman spectroscopy. We focus on the following aspects: (i) the BeTe surface reconstruction and its vanishing during the initial stage of overgrowth, (ii) the chemical compound formation at the BeTe/CdSe interface, and (iii) the strain in the Use layer and its relaxation with increasing layer thickness. Our results show how the lattice vibrational modes develop from interfacial Cd-Te-bond vibrations to pure CdSe-phonons as the overlayer thickness is increased from 1 to 3 ML, and also reveal how the initial strong compressive strain in the CdSe layer gradually decreases, until at 5 ML relaxation is essentially complete. (C) 2003 Elsevier Science B.V. All rights reserved.