Iron silicides grown by solid phase epitaxy on aSi(111)surface: Schematic phase diagram

Abstract

We have determined the schematic phase diagram in detail with high reliability for Fe silicides grown by solid phase epitaxy (SPE) on a $\mathrm{Si}(111)7\ifmmode\times\else\texttimes\fi{}7$ surface at wide Fe coverage $(0.2--56\phantom{\rule{0.3em}{0ex}}\mathrm{monolayers})$ and subsequent annealing temperatures from 300 to $800\phantom{\rule{0.2em}{0ex}}\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$. In the SPE growth, $\ensuremath{\delta}\text{\ensuremath{-}}7\ifmmode\times\else\texttimes\fi{}7$, $1\ifmmode\times\else\texttimes\fi{}1$, $\mathrm{bcc}\text{\ensuremath{-}}\mathrm{Fe}(111)1\ifmmode\times\else\texttimes\fi{}1$, $2\ifmmode\times\else\texttimes\fi{}2$, $c(8\ifmmode\times\else\texttimes\fi{}4)$, $3\mathrm{D}\text{\ensuremath{-}}2\ifmmode\times\else\texttimes\fi{}2$ $(\ensuremath{\alpha}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2})$, $\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3}\text{\ensuremath{-}}R30\ifmmode^\circ\else\textdegree\fi{}$, $\ensuremath{\beta}\text{\ensuremath{-}}{\mathrm{FeSi}}_{2}$, and fine polycrystalline phases are formed on the $\mathrm{Si}(111)$ surface depending on Fe coverage and annealing temperature. We have characterized the surface periodic structures and morphologies of all the above Fe silicide phases using low-energy electron diffraction and scanning tunneling microscopy. Reflection high-energy electron diffraction also has been used to determine three-dimensional structures. Based on the overall view regarding the formations and changes of Fe silicide phases on a $\mathrm{Si}(111)$ surface, we discuss the growth mechanisms.