Synthesis and Characterization of Manganese-Rich Silicide (α-Mn₅Si₃, β-Mn₅Si₃, and β-Mn₃Si) Nanowires

Abstract

The Mn–Si binary phase diagram contains seven distinct equilibrium phases; however, to date, only two phases have been reported in nanowire (NW) morphology. We report the simple reaction of Mn vapor with a Si substrate in a H2 atmosphere to lead to the formation of NW mixtures of MnSi and three new NW phases α-Mn5Si3, β-Mn5Si3, and β-Mn3Si, with the more Mn-rich phases formed at progressively higher temperatures from 800 to 940 °C identified using electron diffraction, together with other structural characterization techniques. Furthermore, the observation of β-Mn5Si3 NWs having the D8m W5Si3 structure type, which is a structure never observed in the Mn–Si system, represents the first report of Mn5Si3 polymorphism. The purposeful use of excess metal species and intentional limitation of vaporous Si species during NW synthesis has led to the first synthesis of manganese-rich silicide NWs.