Since the initial report on the epitaxial growth of α-Fe films on hydrogen-terminated Si(111) surfaces at 300 K, two in-plane orientation relationships, twinned and aligned epitaxy, have been suggested. In this paper, the epitaxial growth of Fe on Si(111) is further examined in detail by x-ray-diffraction θ-2θ scans, x-ray-diffraction φ scans, transmission electron microscopy, and reflection high-energy electron diffraction. Twinned epitaxy at the Fe/Si interface is established, i.e., (111${)}_{\mathrm{\alpha }\mathrm{-}\mathrm{Fe}}$∥(111${)}_{\mathrm{Si}}$ and [1¯10${]}_{\mathrm{\alpha }\mathrm{-}\mathrm{Fe}}$∥[11¯0${]}_{\mathrm{Si}}$. As the film thickness increases, the formation of twins in the epitaxial α-Fe films is observed. The apparent ‘‘aligned epitaxy’’ is the result of twinning in the α-Fe film. The formation of twins in the epitaxial α-Fe film is attributed to the limited mobility at 300 K. The dominance of twinned epitaxy at the interface suggests that the influence of the second-nearest-neighbor interaction between Fe and Si atoms near the interface is important.

• Received 19 July 1993

DOI:https://doi.org/10.1103/PhysRevB.48.14729