Formation of strained iron silicide nanodots by Fe deposition on Si nanodots on oxidized Si (111) surfaces

We studied the epitaxial growth of iron silicide (ε-FeSi,β-FeSi₂, and α-FeSi₂) nanodots on Si (111) substrates by Fe deposition on Si nanodots on Si (111) substrates with ultrathin Si oxide films using reflection high-energy electron diffraction, scanning tunneling microscopy, and transmission electron microscope (TEM). We formed almost single phase iron silicide nanodots by controlling the Fe deposition conditions; growth temperature, deposition rate, and amount. The ε-FeSi or α-FeSi₂ nanodots were epitaxially grown in a dome shape with an average size of ~50.3em0exnm and an ultrahigh density (>10¹²0.3em0excm^-2) on the surface. We formed ~2-nm high and ~8-nm wide β-FeSi₂ nanodots in a dome shape with a density of ~5×10¹¹0.3em0excm^-2 on the surface. Cross-sectional TEM images revealed that the β-FeSi₂ growth continued beneath the Si surface. The part of the β-FeSi₂ nanodot beneath the surface was a disk shape, which was ~50.3em0exnm thick and ~200.3em0exnm wide, with an abrupt interface parallel to the Si (111) plane. The nanodots were epitaxially grown and had almost no misfit dislocations near the β-FeSi₂∕Si interface, which were strained by the lattice mismatch. The size distribution of the iron silicide dots was determined by Ostwald ripening with the activation energy of dot edge mobility of ~1.30.3em0exeV.