Electrical and thermal transport properties of medium-entropy Si Ge Sn  alloys

Wang, Duo; Liu, Lei; Chen, Mohan

doi:10.1016/j.actamat.2020.08.053

Cited by 16 publications

(10 citation statements)

References 100 publications

(114 reference statements)

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“…Figure 3(e) shows the phonon density of states (PDOS) and partition ratio (PR) of the multihyperuniform mixture. Although the overall shape of the PDOS is similar to that of the random system [49], we observe a gap almost opens around 280 cm −1 (corresponding to a temperature of about 400 K), leading to diminishing PR modes in the vicinity of this frequency, and a reduction in the thermal conductivity.…”

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confidence: 58%

“…Here we address this enduring issue by comparing the energies of our DHU structures with those of random and SQS systems. In particular, we perform molecular dynamics simulations with the Stillinger-Weber potential parameterized for Si-Ge-Sn alloys [46][47][48], which has been used to study thermal transport of these alloys [49], and compute the energy difference using the DHU system's energy as the reference. We perform calculations for different supercell sizes (N = 5832 and N = 46656 atoms), and benchmark the energy differences with the density functional theory (see the Supplemental Material for calculation parameters) results of systems with N = 216 atoms.…”

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confidence: 99%

“…Here we use the multihyperuniform structure as the reference and set its energy to zero; in the plot "DFT-216" refers to DFT results with a supercell of 216 atoms, and "SW-5832" and "SW-46656" refer to MD results with a supercell of 5832 and 46656 atoms, respectively. Band structures of the multihyperuniform (b), SQS (c), and random (d) [49] SiGeSn MEAs. (e) Phonon density of states and partition ratio of SiGeSn MEA with the multihyperuniform structure.…”

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confidence: 99%

“…ence of the long-range order on the electronic structure and thermal transport properties of the SiGeSn MEA remains elusive, which we address in our current work. We first calculate the band structure of the SiGeSn MEA with the multihyperuniform and SQS structure and use the previously computed band structure of the random structures for comparison [49]. Figures 3(c), (d), and (e) reveals that all the three systems have direct band gaps at the Γ point and the corresponding band gaps increase from 0.28, 0.36, to 0.50 eV for the random, SQS, and multihyperuniform systems, respectively.…”

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confidence: 99%

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Multihyperuniform Long-Range Order in Medium-Entropy Alloys

Chen¹,

Jiang²,

Wang³

et al. 2021

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We provide strong numerical evidence for a hidden multihyperuniform long-range order (MHLRO) in SiGeSn medium-entropy alloys (MEAs), in which the normalized infinite-wavelength composition fluctuations for all three atomic species are completely suppressed as in a perfect crystalline state. We show this MHLRO naturally leads to the emergence of short-range order (SRO) recently discovered in MEAs, which results in stable lower-energy states compared to alloy models with random or special quasi-random structures (SQSs) possessing no atomic SROs. The MHLRO MEAs approximately realize the Vegard's law, which offers a rule-of-mixture type predictions of the lattice constants and electronic band gap, and thus can be considered as an ideal mixing state. The MHLRO also directly gives rise to enhanced electronic band gaps and superior thermal transport properties at low temperatures compared to random structures and SQSs, which open up novel potential applications in optoelectronics and thermoelectrics. Our analysis of the SiGeSn system leads to the formulation of general organizing principles applicable in other medium-and high-entropy alloys (HEAs), and a highly efficient computational model for rendering realistic large-scale configurations of MEAs and HEAs.

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Multihyperuniform Long-Range Order in Medium-Entropy Alloys

Chen¹,

Jiang²,

Wang³

et al. 2021

Preprint

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“…Their results agreed well with experiment and since then, this technique has been used on wide variety of alloy systems. Recently, Wang et al 18 used the software BoltzTraP2 19 to calculate the electrical transport properties of medium entropy alloy family Si y Ge y Sn x . In this case, the band structure was obtained from supercell calculations using a plane-wave pseuopotential code.…”

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An investigation of high entropy alloy conductivity using first-principles calculations

Raghuraman,

Wang,

Widom

2021

Preprint

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The Kubo-Greenwood equation, in combination with the first-principles Korringa-Kohn-Rostoker Coherent Potential Approximation (KKR-CPA) can be used to calculate the DC residual resistivity of random alloys at T = 0 K. We implemented this method in a multiple scattering theory based ab initio package, MuST, and applied it to the ab initio study of the residual resistivity of the high entropy alloy Al x CoCrFeNi as a function of x. The calculated resistivities are compared with experimental data.We also predict the residual resistivity of refractory high entropy alloy MoNbTaV x W.The calculated resistivity trends are also explained using theoretical arguments.

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Free‐Energy Parameterization and Thermodynamics in Si–Ge–Sn Alloys

Windl

Chien

2022

Physica Status Solidi (b)

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E g ¼ 5.5 eV, silicon with a ¼ 5.43 Å and E g ¼ 1.1 eV, germanium with a ¼ 5.66 Å and E g ¼ 0.7 eV, and Sn with a ¼ 6.49 Å and zero band gap. For the formation of a solid solution, the Hume-Rothery rules [1] state that all elements in the alloy should have the same crystal structure and the same valency, which all four have (Sn only up to a temperature of 286 K), crystallizing in the diamond structure with four valence electrons. They also need to have similar electronegativities, which is true with values of 1.90 for Si, 2.01 for Ge, and 1.96 for Sn, while C's electronegativity with 2.55 is much larger. Finally, the atomic radii should not differ by more than 15%. While C is already 34% smaller than the second-smallest element Si and in combination with its large electronegativity is not expected to form stable solid solutions, we find for the other combinations that Ge is 4.2% larger than Si, Sn is 14.7% larger than Ge, and Sn is 19.5% larger than Si. While the size difference for Sn-Ge is just at the borderline and indicates possible, but not effort-free alloying within at least some solubility range, the situation for Sn-Si looks more difficult. Indeed, looking at the equilibrium phase diagrams, the maximum solubility of Sn in Si is 0.1% [2] more than an order of magnitude smaller than that of Sn in Ge, [3] while Si and Ge have an isomorphous phase diagram with solubility over the entire composition range. [4] The first system realized due to the similar properties of its constituents was the well-behaved Si 1Àx Ge x with full miscibility over the entire composition range. In SiGe alloys, the dependence of the bandgap on the Ge concentration is well known for more than 60 years, where the conduction band minimum changes from the Δ-point on the Si-rich side to the L-point above 85% Ge with a sharp kink at the transition composition. [5] Also, the lattice constant follows closely Vegard's Law with only a small bowing deviation. [6] SiGe was introduced into the semiconductor device market in the 1990s by IBM and has by now become a staple for heterojunction bipolar transistors or as a straininducing layer for CMOS transistors.SiGeC (and to a lesser degree SiC) alloys were closely following SiGe and heavily researched in the 1990s to realize stress-compensated alloys with bandgaps larger than Si. It started with Soref 's conjecture that the bandgap of these alloys might follow a linear/exponential interpolation of the bandgaps of the elemental endpoints. [7] Thus, the bandgap of diamond, with 5.5 eV much larger than those of Ge (0.7 eV) and Si (1.1 eV) was

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Electrical and thermal transport properties of medium-entropy Si Ge Sn alloys

Cited by 16 publications

References 100 publications

Multihyperuniform Long-Range Order in Medium-Entropy Alloys

Multihyperuniform Long-Range Order in Medium-Entropy Alloys

An investigation of high entropy alloy conductivity using first-principles calculations

Free‐Energy Parameterization and Thermodynamics in Si–Ge–Sn Alloys

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