Epitaxial orientation and morphology of β-FeSi₂ on (001) silicon

Epitaxially aligned films of β-FeSi₂ were grown on (001) silicon by reactive deposition epitaxy (RDE), molecular-beam epitaxy (MBE), and solid-phase epitaxy (SPE). Although the matching crystallographic faces, FeSi₂ (100)/Si(001), remained invariant throughout this study, two different azimuthal orientations predominated, depending on the deposition mode and growth temperature. Films with the FeSi₂[010] ∥Si〈110〉 orientation (grown by RDE at typically 500 °C) were of a genuine large-area single-crystal structure; however, the surface morphology was rough due to islanding which always preceeded the formation of a continuous film. Films of the alternative azimuthal orientation FeSi ₂[010]∥Si〈100〉 (which were grown by SPE at typically 250 °C or by MBE at temperatures as low as 200 °C on top of an SPE-grown template) have a much smoother surface morphology. However, there was some loss of purity in the epitaxial alignment at these extremely low temperatures. Excellent RHEED (reflection high-energy electron diffraction) streak patterns were observed for all the films; the technique was used for the determination of azimuthal orientation. In addition, we have shown that it is possible to determine the entire heteroepitaxial relationship using RHEED.