Nb on (110) TiO2 (rutile): growth, structure, and chemical composition of the interface

Thin epitaxial Nb films on the (110) TiO2, (rutile) have been prepared by m olecular beam epitaxy at room temperature. As demonstrated by in-situ refle ction high-energy electron diffraction, Auger electron spectroscopy and TEM , a structurally distorted interlayer of about 2-3 nm has formed between Nb and TiO2, in the early growth stages. The formation of the interlayer was the result of a strong chemical reaction at the interface caused by the hig h oxygen affinity of niobium. The first two monolayers of Nb were oxidized, resulting in the partial reduction of a similar to 2 nm thick TiO2, layer near the interface. On top of the interfacial reaction layer, Nb grew epita xially with the following orientation relationship: (100)[001]Nb//(110)[001 ] TiO2,. In this paper we report the first direct observation of the Nb/TiO 2 interface by high-resolution transmission electron microscopy. Additional ly, electron-energy loss spectra were recorded in a dedicated scanning tran smission electron microscope to determine the chemical composition of the i nterfacial interlayer with high spatial resolution. The formation of the in terlayer and the corresponding epitaxial orientation are discussed in detai l. (C) 2000 Published by Elsevier Science B.V. All rights reserved.