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

Abstract

The epitaxial growth by reactive deposition of $\ensuremath{\epsilon}\text{-FeSi}$ and $\ensuremath{\beta}{\text{-FeSi}}_{2}$ 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 $\ensuremath{\epsilon}\text{-FeSi}$ and $\ensuremath{\beta}{\text{-FeSi}}_{2}$ were formed at low and high iron coverage, respectively. A $\ensuremath{\epsilon}\text{-FeSi}$ to $\ensuremath{\beta}{\text{-FeSi}}_{2}$ 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 $\ensuremath{\beta}{\text{-FeSi}}_{2}$ phase. A direct comparison of the diffraction and microscopy data shows that nanodots of different phases also exhibit different shapes, being the $\ensuremath{\epsilon}\text{-FeSi}$ $(\ensuremath{\beta}{\text{-FeSi}}_{2})$ nanodots smaller (larger) and with a low (high) aspect ratio.