Characterization of the interfacial region of epitaxial TlBiSe2 thin filmsby infrared spectroscopy and transmission electron microscopy

TlBiSe2 epitaxial thin films were grown on NaCl substrates by electron beam evaporation under different growth conditions. The as-grown films were cha racterised by infrared reflectance measurements and transmission electron m icroscopy observations. It is determined that the interfacial region of suc h films under certain supersaturation conditions presents a new fee cubic p hase sub-layer which grows with the substrate lattice parameter to a consid erable thickness. The occurrence of this phase has a dependence on the depo sition rate which is evident particularly when low substrate temperatures a re employed in the growth process. A plausible explanation is offered for t he observed cubic phase in terms of a pressure induced structural modificat ion. Finally, it is shown that the complimentary nature of the two methods allows a complete structural and electrical characterisation of thin film s tructures. (C) 1999 Elsevier Science S.A. All rights reserved.