Electronic and related properties of crystalline semiconducting iron disilicide

Abstract

Band structure calculations for β-FeSi2 have been performed by the linear muffin-tin orbital method within the local density approximation scheme including exchange and correlation effects. A detailed analysis of the conduction and valence band structure around high-symmetry points has shown the existence of a quasidirect band gap structure in the material. It is experimentally confirmed that between the threshold energy of optical interband transition of 0.73 eV and the first direct gap transition with appreciable oscillator strength at about 0.87 eV there is a region in which direct transition of low oscillator strength and indirect transitions overlap. That explains the tricky behavior of β-FeSi2 in experimental investigations demonstrating it to be either a direct or indirect gap semiconductor.

Structural, electronic and optical properties of a new binary phase – ruthenium disilicide

“…shift of eigenvalues in the energy range analyzed due to so-called correlation effects and it may be rather different for various materials. Nevertheless, for some silicides, namely for iron disilicide, good agreement between theoretically predicted and experimental values was obtained [11,27]. This effect could be ascribed to the fact that corresponding eigenfunctions at extrema points of the band structure were mainly composed by d-electron states of iron atoms.…”

Phase transformation in FeSi2 nanowires

“…Both indirect and direct gaps with a large energy range of 0.4-1.0 eV have been reported in theoretical and experimental papers [6][7][8][9][10]. Recent work shows that b-FeSi 2 has an indirect gap of a few tens of milli-electron-volts less than the first direct transition of appreciable oscillator strength located at the Y point in the Brillouin zone [11][12][13][14]. Much of the discrepancy in the literature likely results from the strong influence of strain on the band gap of b-FeSi 2 [15].…”

Indirect optical absorption of single crystalline β-FeSi2

“…From the analysis of the energy dependence of the absorption coefficient, in most reports it is argued that β-FeSi 2 has a direct band gap [1,2,6,7,8,9,10,11,12], but a few papers report an indirect gap lower than the direct one by some tens of meV. [13,14,15]. The reported values of the band gap are 0.80 -0.95 eV for direct gap and 0.7 -0.78 eV for indirect one.…”