Indirect optical absorption and origin of the emission from β-FeSi2 nanoparticles: Bound exciton (0.809 eV) and band to acceptor impurity (0.795 eV) transitions

Abstract

We investigated the optical absorption of the fundamental band edge and the origin of the emission from β-FeSi2 nanoparticles synthesized by ion-beam-induced epitaxial crystallization of Fe+ implanted SiO2/Si(100) followed by thermal annealing. From micro-Raman scattering and transmission electron microscopy measurements it was possible to attest the formation of strained β-FeSi2 nanoparticles and its structural quality. The optical absorption near the fundamental gap edge of β-FeSi2 nanoparticles evaluated by spectroscopic ellipsometry showed a step structure characteristic of an indirect fundamental gap material. Photoluminescence spectroscopy measurements at each synthesis stage revealed complex emissions in the 0.7–0.9 eV spectral region, with different intensities and morphologies strongly dependent on thermal treatment temperature. Spectral deconvolution into four transition lines at 0.795, 0.809, 0.851, and 0.873 eV was performed. We concluded that the emission at 0.795 eV may be related to a radiative direct transition from the direct conduction band to an acceptor level and that the emission at 0.809 eV derives from a recombination of an indirect bound exciton to this acceptor level of β-FeSi2. Emissions 0.851 and 0.873 eV were confirmed to be typical dislocation-related photoluminescence centers in Si. From the energy balance we determined the fundamental indirect and direct band gap energies to be 0.856 and 0.867 eV, respectively. An illustrative energy band diagram derived from a proposed model to explain the possible transition processes involved is presented.

Investigation of various phases of Fe–Si structures formed in Si by low energy Fe ion implantation

“…Because of this reason, b-FeSi 2 has been extensively studied for its potential application as optoelectronic devices in the infrared region. However, the nature of the band gap is questionable since evidence of an indirect gap, slightly lower than the direct one, has been found [6]. Also, amorphous-FeSi 2 shows semiconducting properties [5].…”

Magnetron-sputter epitaxy of β-FeSi2(220)/Si(111) and β-FeSi2(431)/Si(001) thin films at elevated temperatures

“…[1][2][3][4] Although various material technologies have been employed and developed to improve the heteroepitaxy, 5-7 the characteristics of b-FeSi 2 thin films are still far from the requirements needed for device applications in industry. [1][2][3][4] Although various material technologies have been employed and developed to improve the heteroepitaxy, 5-7 the characteristics of b-FeSi 2 thin films are still far from the requirements needed for device applications in industry.…”

“…[1][2][3][4] Although various material technologies have been employed and developed to improve the heteroepitaxy, 5-7 the characteristics of b-FeSi 2 thin films are still far from the requirements needed for device applications in industry. Meanwhile, the 120 -rotation symmetry of the atomic arrangement in Si(111) plane causes three 120 -rotated variants of [001]b-FeSi 2 (110)// [1][2][3][4][5][6][7][8][9][10]Si(111). 6,8 In general, the growth of b-FeSi 2 on Si(111) results in b-FeSi 2 (110) or b-FeSi 2 (101)//Si(111) due to the close lattice constants of b and c [hereafter, for the sake of brevity, only b-FeSi 2 (110)//Si(111) will be referred to as the growth direction].…”

“…6,8 In general, the growth of b-FeSi 2 on Si(111) results in b-FeSi 2 (110) or b-FeSi 2 (101)//Si(111) due to the close lattice constants of b and c [hereafter, for the sake of brevity, only b-FeSi 2 (110)//Si(111) will be referred to as the growth direction]. One is [010]b-FeSi 2 (100)// [1][2][3][4][5][6][7][8][9][10] 1,6,8 Such variations in crystal growth orientation are important for semiconductor processing. 1,6,9 A change in growth conditions, e.g., a decrease in the growth temperature, results in the formation of two other differently oriented domains.…”

Ion-Beam-Induced Epitaxial Recrystallization Method and Its Recent Applications

“…The IBIEC technique has been used as a method to synthesize nanoparticles in Silicon matrix [Lang et al, 2010a[Lang et al, , 2010b. Specifically, the structural properties of the FeSi 2 nanoparticles synthesized in Fe + low dose implanted Si(100) substrates were investigated.…”