Phase formation in iron silicide nanodots grown by reactive deposition epitaxy on Si(111)

摘要

The epitaxial growth by reactive deposition of ε-FeSi and β-FeSi_2 nanodots on Si(111) is studied as a function of Fe coverage. The nanodots density, size, and strain were analyzed by atomic force microscopy and x-ray diffraction. Almost single phase ε-FeSi and β-FeSi_2 were formed at low and high iron coverage, respectively. A ε-FeSi to β-FeSi_2 change in phase formation is observed at Fe coverage of 5.5 nm, which is coincident with the coalescence of the nanodots, the relaxation of the strain in both phases and a discontinuous increase of the grain size of the β-FeSi_2 phase. A direct comparison of the diffraction and microscopy data shows that nanodots of different phases also exhibit different shapes, being the e-FeSi (β-FeSi_2) nanodots smaller (larger) and with a low (high) aspect ratio.