We present photoluminescence (PL) properties of impurity (Al, Mn, Co)-doped β-FeSi2 produced by ion-beam synthesis. The β-Fe(Si1−xAlx)2 sample showed an increase of both the PL intensity and activation energy (Ea) for a nonradiative recombination path. On the contrary, the β-(Fe1−xMnx)Si2 and the β-(Fe1−xCox)Si2 samples reduced the PL intensity and Ea. We found that the doping of Al atoms occupying the Si sites in β-FeSi2 is effective to enhance the 1.54 μm photoluminescence.

Enhancement of 1.54 μm photoluminescence observed in Al-doped β-FeSi2

We have performed a comparative study of structural, electronic and optical properties of Ru 2 Si 3 , Ru 2 Ge 3 , Os 2 Si 3 and Os 2 Ge 3 by means of ultrasoft pseudopotential and full-potential linearized augmented plane wave methods. The estimated difference in the cohesion energy between the low-temperature orthorhombic phase and the high temperature tetragonal one for all these compounds indicates that the former phase is lower in energy with respect to the latter one. All materials in the orthorhombic structure are found to be direct band-gap semiconductors, still some of them in the tetragonal structure display an indirect nature (Os 2 Si 3 ) or a competitive direct-indirect character (Ru 2 Ge 3 ) of the gap. Optical properties are discussed by analyzing the imaginary part of the dielectric function and the dipole matrix elements corresponding to different interband transitions indicating for osmium silicide and germanide the presence of low-energy transitions with an appreciable value of the oscillator strength.

Structural, electronic and optical properties of Ru2Si3, Ru2Ge3, Os2Si3 and Os2Ge3

Floating zone growth and characterization of semiconducting Ru2Si3 single crystals

Directional thermoelectric properties of Ru2Si3

We study the electronic band structure, dielectric, and lattice dynamical properties of FeSi, RuSi and OsSi from first principles using density functional theory. We performed the band structure calculations for these compounds to confirm they are indirect band-gap semiconductors. Density functional perturbation theory is employed to evaluate the Born effective charge tensors, the dielectric permittivity tensors, the phonon frequencies at the Γ-point, and the phonon dispersion curves as well as the corresponding density of states. These calculated results are in reasonable agreement with the experimental data and theoretical values available. From the present calculation we also predict that there exist longitudinal-transverse optical (LO-TO) splittings by 2–32 cm- 1 for these three compounds, which were not observed in previous experiments.

http://iopscience.iop.org/article/10.1209/0295-5075/85/47005/pdf

First-principles studies of the electronic and dynamical properties of monosilicides MSi (M = Fe, Ru, Os)

Growth and structural characterization of semiconducting Ru2Si3

Study of structure and optical properties of β-FeSi2 precipitates formed by ion-implantation of Fe+ in Si(100) and effects of co-implantation of Fe+ and Si+ in amorphous SiO2

Recently, Ru2Si3 has been predicted to be a direct semiconductor with a band gap of ≈0.8 eV. Since the corresponding wavelength of this potential light emitter coincides with the absolute absorption minimum of glass fibers of 1.5 μm, considerable attention has been attracted. Measurements of the temperature dependence of the electrical resistivity of silicide films on insulating substrates were carried out in van der Pauw geometry. The results were explained by assuming carrier hopping over grain boundaries. The optical absorption coefficient was measured on thin films grown on various substrates, on self-sustaining films, where the substrate was partly removed and on a single crystal by photothermal deflection spectroscopy. A direct band gap at 0.84 eV was found. The absorption coefficient is very low up to ≈1.5 eV, likely due to a low density of states, and then strongly increases at higher energies. The experimental results qualitatively confirm the predictions of the band structure calculations.

/pdf/electrical-and-optical-characterization-of-semiconducting-qt2df92zv2.pdf

D. Lenssen

Papers

Growth and structural characterization of semiconducting Ru2Si3

Study of structure and optical properties of β-FeSi2 precipitates formed by ion-implantation of Fe+ in Si(100) and effects of co-implantation of Fe+ and Si+ in amorphous SiO2

Electrical and optical characterization of semiconducting Ru2Si3 films and single crystals

Structural, electrical and optical characterization of semiconducting Ru 2 Si 3

Formation of β-FeSi2 precipitates at the SiO2/Si interface by Fe+ ion implantation and their structural and optical properties