Organometallic Routes into the Nanorealms of Binary Fe-Si Phases

Abstract

The Fe-Si binary system provides several iron silicides that have varied and exceptional material properties with applications in the electronic industry. The well known Fe-Si binary silicides are Fe3Si, Fe5Si3, FeSi, α-FeSi2 and β-FeSi2. While the iron-rich silicides Fe3Si and Fe5Si3 are known to be room temperature ferromagnets, the stoichiometric FeSi is the only known transition metal Kondo insulator. Furthermore, Fe5Si3 has also been demonstrated to exhibit giant magnetoresistance (GMR). The silicon-rich β-FeSi2 is a direct band gap material usable in light emitting diode (LED) applications. Typically, these silicides are synthesized by traditional solid-state reactions or by ion beam-induced mixing (IBM) of alternating metal and silicon layers. Alternatively, the utilization of organometallic compounds with reactive transition metal (Fe)-carbon bonds has opened various routes for the preparation of these silicides and the silicon-stabilized bcc- and fcc-Fe phases contained in the Fe-Si binary phase diagram. The unique interfacial interactions of carbon with the Fe and Si components have resulted in the preferential formation of nanoscale versions of these materials. This review will discuss such reactions.

Fabrication of FeSi and Fe3Si compounds by electron beam induced mixing of [Fe/Si]2 and [Fe3/Si]2 multilayers grown by focused electron beam induced deposition

“…F e 3 Si and F e 5 Si 3 are room-temperature ferromagnets attractive for spintronics [5,6]. In particular, F e 3 Si is a pseudo-Heusler alloy with D0 3 structure, equivalent to the L2 1 structure of full-Heusler compounds, which are predicted to be half-metallic [7,8].…”

“…Conventionally, the preparation of Fe-Si binary alloys takes place by means of solid-state reactions [9,10]. Alternatively, organometallic precursors were used to fabricate F e 3 Si and F e 5 Si 3 nanoparticles by pyrolysis [6] and iron silicides by chemical vapor deposition(CVD) [11]. CVD was also employed to grow polycrystalline F eSi thin films and freestanding F eSi nanowires from the organometallic single source precursor F e(SiCl 3 ) 2 (CO) 4 [12,13].…”

Grazing incidence X-ray diffraction (GIRXD) study of the phase composition of SiC x Fe y and SiC x N y Fe z thin films

“…The FTIR spectra of these layers have peaks corresponding to the stretching vibrations of Fe-Si bonds (480 cm -1 , 630 cm -1 , 1070 cm -1 ) [6], and the sharp peak at 1550-1600 cm -1 belongs to the stretching vibrations of C-C bonds [7]. The presence of carbon nanotubes within the SiC x Fe y films was confirmed by Raman spectroscopy.…”

A Radical Twist to the Versatile Behavior of Iron in Selective Methane Activation

“…The active site can therefore be regarded as a local mixed iron silicide carbide phase (Fe x Si y C z with x =1, y =1, and z =2) with an iron atom in a trigonal environment embedded within a seemingly very inert, porous SiO 2 matrix. As there is a vast amount of literature in the areas of for example, metallurgy, mineralogy, and materials electronics, further characterization studies will have to clarify the precise nature of this peculiar active center 8. This is possible by using additional methods, such as Mössbauer spectroscopy (MS), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS) (preferably in combination with TEM), although each of these methods, as well as the originally reported EXAFS measurements, will require a set of well-defined iron silicide and iron carbide reference compounds for proper spectral analysis.…”