Formation of ultrahigh density and ultrasmall coherent β-FeSi2 nanodots on Si (111) substrates using Si and Fe codeposition method

Abstract

We studied the formation of β-FeSi2 nanodots by codeposition at disilicide stoichiometric deposition rates of Fe and Si on Si (111) substrates covered with ultrathin SiO2 films. Hemispherical β-FeSi2 nanodots with an ultrahigh density (>1012cm−2) and with a narrow size distribution at the average size of ∼5nm diameter were epitaxially grown by the codeposition at 500°C on ultrathin SiO2 films with predeposited Si. High-resolution transmission electron microscope observations showed that the formed nanodots were strained with a main configuration of β-FeSi2 (110)∕Si (111). We propose the formation mechanism that a reaction between the SiO2 films and deposited Si atoms formed voids in the SiO2 films to work as nucleation sites, followed by direct β-FeSi2 formation from Fe and Si without passing through other iron silicide phases.