FORMATION OF TWINS DURING EPITAXIAL-GROWTH OF ALPHA-IRON FILMS ON SILICON (111)

Since the initial report on the epitaxial growth of alpha-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 theta-2theta scans, x-ray-diffraction phi scans, transmission electron microscopy, and reflection high-energy electron diffraction. Twinned epitaxy at the Fe/Si interface is established, i.e., (111)alpha-Fe parallel-to (111)Si and [110BAR]alpha-Fe parallel-to [110BAR]Si. As the film thickness increases, the formation of twins in the epitaxial alpha-Fe films is observed. The apparent ''aligned epitaxy'' is the result of twinning in the alpha-Fe film. The formation of twins in the epitaxial alpha-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.