Growth behavior and microstructure of Co-Ge films prepared on GaAs substrate by high-temperature sequential deposition

The growth behavior and microstructure of Co-Ge/GaAs films prepared by the high-temperature sequential deposition (HTSD) method have been investigated using X-ray diffraction, cross-sectional transmission electron microscopy, X-ray photoelectron sepectroscopy and atomic force microscopy. Three germa nides were formed in the films at temperatures ranging from 300 to 600 degr eesC, Polycrystalline CoGe with poor crystallinity was formed at 300 degree sC, On the other hand, epitaxial Co5Ge7 were formed at 400 and 500 degreesC , The epitaxial orientations for the Co5Ge7 films formed at 400 and 500 deg reesC are [0 0 1] (1 0 0) Co(5)Ge(7)parallel to [1 1 0] (0 0 1) Ge parallel to [1 1 0] (0 0 1) GaAs and [1 0 0] (0 0 1) Co(5)Ce(7)parallel to [1 1 0] (0 0 1) Ge parallel to [1 1 0] (001) GaAs, respectively. Then, at 600 degre esC polycrystalline CoGe2 was formed in the film. Based on the experimental results, the solid-state reaction mechanism for Co-Ge binary system and th e epitaxial growth mode for Co5Ge7 are discussed. (C) 2001 Elsevier Science B.V. All rights reserved.