Metallic and Ionic Fe Induced Growth of Si−SiO_<i>x</i> Core−Shell Nanowires

Abstract

Si−SiO_<i>x</i> core−shell nanowires with a length of hundreds of micrometers and average diameters of 40−90 nm were fabricated by directly heating Si wafers coated with metallic Fe. These novel core−shell nanowires have a diamond structure for their ultrathin Si cores with a diameter of 5−8 nm aligned along the ⟨111⟩ growth directions inside much thicker amorphous SiO_<i>x</i> shells. A new temperature-dependent alloy, metallic and ionic Fe (Fe−FeO_<i>x</i>), catalyzed solid−liquid−solid mechanism is proposed to explain the growth of Si−SiO_<i>x</i> core−shell nanowires based on both the synthesis conditions and microstructural characterizations.