Ion beam synthesis of Mg₂Si

A simple phase transformation strategy for converting silicon nanowires into metal silicide nanowires: Magnesium silicide

“…The preparation and thermoelectric property characterization of bulk ingots, thin films, and nanocrystals of Mg 2 Si have been reported numerous times in the literature [16][17][18][19][20][21][22]. The high vapor pressure, and consequently the low condensation coefficient, of magnesium [19] coupled with its high propensity to oxidation [23,24] prevent the use of chemical vapor deposition (CVD) for the synthesis of Mg 2 Si nanowires. Alternately, the phase transformation of pre-synthesized silicon nanowires into Mg 2 Si nanowires can be employed as a strategy for their synthesis.…”

Optical properties of multilayer materials based on silicon and nanosized magnesium silicide crystallites

“…In [9], by Fourier spectroscopy on silicon with incorporated precipitates of Mg 2 Si obtained by ion incorporation of low doses of magnesium (5⋅10 16 to 1⋅10 17 cm -3 ) into the silicon and additional annealing at 500 o C, three absorption bands were observed with wavenumbers 227-235, 273-279, and 350-355 cm -1 , and a tendency was seen toward the appearance of an additional peak at wavenumbers above 400 cm -1 . Transmission spectra with more peaks are observed for low incorporation doses, which makes it possible to hypothesize that in this case, nanocrystallites of magnesium silicide are formed in the silicon.…”

“…The technology for obtaining thin epitaxial films based on silicon is complicated by the low magnesium/silicon coefficient of adhesion and its revaporization at temperatures above 400 o C [8]. Nevertheless, formation of incorporated nanosized Mg 2 Si crystallites in silicon by the ion incorporation method [9] or by the solid-phase epitaxy method [10,11] is of interest to both basic and applied research for designing silicon-containing materials with new optical properties.We know [12] that Mg 2 Si has an antifluorite structure and belongs to the space group Fm3m, the space group for an octahedron (O h ). From phonon vibration theory (within the harmonic expansion) [13,14] for crystals with a center of symmetry, one-phonon optical transitions (resonances) are forbidden.…”

“…The technology for obtaining thin epitaxial films based on silicon is complicated by the low magnesium/silicon coefficient of adhesion and its revaporization at temperatures above 400 o C [8]. Nevertheless, formation of incorporated nanosized Mg 2 Si crystallites in silicon by the ion incorporation method [9] or by the solid-phase epitaxy method [10,11] is of interest to both basic and applied research for designing silicon-containing materials with new optical properties.…”

“…At higher doses, probably larger crystallites were formed with properties close to the bulk properties. Nevertheless, the authors of [9] as before used the one-phonon resonance theory [13,14] for all the samples, and focused their attention only on the frequency 273-279 cm -1 , close to the frequency of the transverse optical phonon in Mg 2 Si [18]. However, the observed additional bands may be connected with two-phonon processes [19] in different crystallographic directions of the Mg 2 Si crystal lattice, which was not considered in [9].…”