Semiconducting properties of Mg2Si single crystals

Morris, Robert G.

doi:10.31274/rtd-180813-3350

Cited by 10 publications

(7 citation statements)

References 27 publications

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“…All the compounds (Mg 2 Si, Mg 2 Ge, and Mg 2 Sn) share a similar electronic band structure consisting of two closely lying conduction bands (Figure and Table ). − However, while the bottom of the conduction band in Mg 2 Si and Mg 2 Ge is dominated by the light electron band (C L band) that has its origin in the 3p orbital of Mg hybridized with the s orbital and d-e g orbital of Si or Ge, the bottom of the conduction band of Mg 2 Sn is dominated by the heavy electron band (C H band) arising from hybridization between the 3s orbital of Mg and the d-t 2g orbital of Sn. − This implies that via the formation of solid solutions of Mg 2 Si 1– x Sn x and Mg 2 Ge 1– x Sn x , band convergence must take place at some particular value of x where the band edges of the light and heavy conduction bands attain comparable energy. When this happens, the band degeneracy ( N v ) of the system is increased, which leads to a significant enhancement of the density of states (DOS) effective mass m * = N v 2/3 m b * without increasing the band effective mass ( m b *).…”

Section: Introductionmentioning

confidence: 99%

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Yin

Yan

et al. 2016

Chem. Mater.

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The dependence of the electronic band structure of Mg2Si0.3–x Ge x Sn0.7 and Mg2Si0.3Ge y Sn0.7–y (0 ≤ x, and y ≤ 0.05) ternary solid solutions on composition and temperature is explained by a simple linear model, and the lattice thermal conductivity of solid solutions with different Si/Ge/Sn ratios is predicted by the Adachi model. The experimental results show excellent consistency with the calculations, which suggests that the approach might be suitable for describing the electronic band structure and the lattice thermal conductivity of other solid solutions using these simple calculations. Beyond this, it is observed that the immiscible gap in the Mg2Si1–x Sn x binary system is narrowed via the introduction of Mg2Ge. Moreover, for the Sb-doped solid solutions Mg2.16(Si0.3Ge y Sn0.7–y )0.98Sb0.02 (0 ≤ y ≤ 0.05), the energy offset between the light conduction band and the heavy conduction band at higher temperatures (500–800 K) will decrease with an increase in Ge content, thus making a contribution to the conduction band degeneracy and enhancing the power factor in turn. Meanwhile, mass fluctuation and strain field scattering processes are enhanced when Ge is substituted for Sn in Mg2.16(Si0.3Ge y Sn0.7–y )0.98Sb0.02 (0 ≤ y ≤ 0.05) because of the large discrepancy between the mass and size of Ge and Sn, and the lattice thermal conductivity is decreased as a consequence. Thus, the thermoelectric performance is improved, with the figure of merit ZT being >1.45 at ∼750 K and the average ZT value being between 0.9 and 1.0 in the range of 300–800 K, which is one of the best results for Sb-doped Mg2Si1–x–y Ge x Sn y systems with a single phase.

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Section: Introductionmentioning

confidence: 99%

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Yin

Yan

et al. 2016

Chem. Mater.

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“…We estimated an activation energy for this 325 °C curve as E a ≈ 50 meV. This value is much smaller than a semiconductor band gap of 0.65–0.8 eV in undoped Mg 2 Si. − …”

Section: Resultsmentioning

confidence: 81%

“…Magnesium silicide, Mg 2 Si, is a semiconducting material with a narrow band gap of about 0.65–0.8 eV and interesting physical properties. − At ambient conditions, Mg 2 Si crystallizes in a cubic antifluorite (CaF 2 )-type structure (space group no. 225 – Fm 3̅ m , Z = 4) (Figure a).…”

Section: Introductionmentioning

confidence: 99%

Unconventional Electronic Properties of Mg₂Si Thermoelectrics Revealed by Fast-Neutron-Irradiation Doping

et al. 2016

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In this work, we systematically investigated the electrical resistivity, Hall, and magnetoresistance effects of Aldoped Mg 2 Si thermoelectrics, irradiated with a fluence of fast neutrons and consequently isochronally annealed at moderate high temperatures up to 500 °C. We found that the fastneutron bombardment itself only slightly modified the electronic properties. Meanwhile, a series of the postirradiation high-temperature anneals affected the properties dramatically. Thus, after annealing at temperatures of 275−325 °C, Mg 2 Si:Al showed pronounced jumps in both the electrical resistivity and the Hall constant values by several orders of magnitude. This unexpected electronic transition corresponded to a significant variation in the carrier concentration. We proposed that this unusual electronic transition may be related to temperature-assisted chemical bonding of the radiation defects that can involve free charge carriers in the sample, thereby tuning dramatically its transport properties. We proposed a simple model for Mg 2 Si:Al thermoelectrics, which links the chemical bonding of the interstitial Mg ions with the electronic properties of this material. This finding suggests a new avenue to tuning of electronic properties and unconventional electronic transitions in materials with a high concentration of defects.

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“…One can solve the Poisson equation of the barrier region (depletion region) on both sides of the interface to obtain the contact potential difference (band bending) of Mg 2 Si/4H‐SiC heterojunction. Assuming that Mg 2 Si/4H‐SiC is a mutant heterojunction and the Poisson equations on both sides of the interface are, respectively, the following:

\frac{d^{2} V_{1} ((), x)}{normald x^{2}} goodbreak= \frac{{italicqN}_{1}}{ε_{1}} ((), x_{1} < x < 0),

\frac{d^{2} V_{2} ((), x)}{normald x^{2}} goodbreak= goodbreak- \frac{{italicqN}_{2}}{ε_{2}} ((), 0 < x < x_{2}),

where

x_{1}

V_{1}

N_{1} = 2 \times 10^{16} {cm}^{- 3}

, and

ε_{1} = 20

28 denote the barrier width, potential, carriers concentration, and static dielectric constant in the Mg 2 Si side, respectively;

x_{2}

V_{2}

N_{2} = 2.3 \times 10^{17} {cm}^{- 3}

, and

ε_{2} = 10

26 denote the corresponding parameter in the 4H‐SiC side. Solving Equations () and () will yield the following:

\frac{normalΔ V_{1}}{normalΔ V_{2}} goodbreak= \frac{ε_{2} N_{2}}{ε_{1} N_{1}},

where

normalΔ V_{1}

and

normalΔ V_{2}

are the values of band bending in Mg 2 Si and 4H‐SiC sides, respectively.…”

Section: Resultsmentioning

confidence: 99%

Determination of the interface band alignment of Mg₂Si/4H‐SiC heterojuction for potential photodetector application

Liao

Xie

Xiao

et al. 2021

Surface & Interface Analysis

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The Mg2Si/4H‐SiC heterojunction was prepared by radio frequency (RF) magnetron sputtering technique. The binding energies of Mg 2p, Si 2p, and C 1s core levels and the maxima of valence band were measured by X‐ray photoelectron spectroscopy (XPS). Using the optical bandgap of Mg2Si (0.78 eV) and 4H‐SiC (3.25 eV), the band offsets of valence band (VBO) and conduction band (CBO) at Mg2Si/4H‐SiC interface were identified as 1.47 and 1.00 eV, respectively. The band alignment was evaluated to be type‐I band alignment. The Mg2Si/4H‐SiC heterojunction could be a promising candidate for the infrared (IR) photodetector.

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Semiconducting properties of Mg2Si single crystals

Cited by 10 publications

References 27 publications

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Unconventional Electronic Properties of Mg₂Si Thermoelectrics Revealed by Fast-Neutron-Irradiation Doping

Determination of the interface band alignment of Mg₂Si/4H‐SiC heterojuction for potential photodetector application

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Semiconducting properties of Mg2Si single crystals

Cited by 10 publications

References 27 publications

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg2Si1–x–yGexSny Ternary Solid Solution

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg2Si1–x–yGexSny Ternary Solid Solution

Unconventional Electronic Properties of Mg2Si Thermoelectrics Revealed by Fast-Neutron-Irradiation Doping

Determination of the interface band alignment of Mg2Si/4H‐SiC heterojuction for potential photodetector application

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Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Optimization of the Electronic Band Structure and the Lattice Thermal Conductivity of Solid Solutions According to Simple Calculations: A Canonical Example of the Mg₂Si_1–x–yGe_xSn_y Ternary Solid Solution

Unconventional Electronic Properties of Mg₂Si Thermoelectrics Revealed by Fast-Neutron-Irradiation Doping

Determination of the interface band alignment of Mg₂Si/4H‐SiC heterojuction for potential photodetector application