Energy band structure and optical response function of icosahedral<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mtext>B</mml:mtext><mml:mrow><mml:mn>12</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mtext>As</mml:mtext></mml:mrow><mml:mn>2</mml:mn></mml:msub></mml:mrow></mml:math>: A spectroscopic ellipsometry and first-principles calculational study

Bakalova, S.; Gong, Yinyan; Cobet, Christoph; Esser, N.; Zhang, Y.; Edgar, James H.; Dudley, Michael; Kuball, Martin

doi:10.1103/physrevb.81.075114

Cited by 24 publications

(36 citation statements)

References 25 publications

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“…(2), typically results in an overestimation of the maximum T for the boundary between a single-phase region (α) and a miscibility gap (α + α ), and thus it should be taken as an upper limit. Since boron subpnictides are usually synthesized at T 1300 K [19,21,24,[67][68][69], one can, based on our prediction, expect the intermixing of As and P atoms at the diatomic chain sites, i.e., a formation of B 12 (As 1−x P x ) 2 , when synthesizing a mixture between B 12 P 2 and B 12 As 2 . Such an intermixing of As and P atoms in B 12 (As 1−x P x ) 2 is also expected to possibly quench to room temperature, at which B 12 (As 1−x P x ) 2 stays as a metastable state due to a lack of atomic diffusion at low temperature, due to strong interatomic covalent bonds in icosahedral boron-rich solids.…”

Section: Sa-sqs Modelmentioning

confidence: 71%

“…1(b)]. Owing to their crystal structures, governed by B 12 clusters, B 12 As 2 and B 12 P 2 display several highly valued properties [17][18][19], e.g., * anekt@ifm.liu.se high chemical stability, high melting point (T m > 2300 K), and wide electronic band gap (E g > 3 eV). As a consequence, the two subpnictides are promising materials for fabrication of betavoltaic cells [20] and high-temperature electronic [21] and thermoelectric devices [22,23].…”

Section: Introductionmentioning

confidence: 99%

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First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

2017

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We examine the thermodynamic stability of compounds and alloys in the ternary B-As-P system theoretically using first-principles calculations. We demonstrate that the icosahedral B 12 As 2 is the only stable compound in the binary B-As system, while the zinc-blende BAs is thermodynamically unstable with respect to B 12 As 2 and the pure arsenic phase at 0 K, and increasingly so at higher temperature, suggesting that BAs may merely exist as a metastable phase. On the contrary, in the binary B-P system, both zinc-blende BP and icosahedral B 12 P 2 are predicted to be stable. As for the binary As-P system, As 1−x P x disordered alloys are predicted at elevated temperature-for example, a disordered solid solution of up to ∼75 at.% As in black phosphorus as well as a small solubility of ∼1 at.% P in gray arsenic at T = 750 K, together with the presence of miscibility gaps. The calculated large solubility of As in black phosphorus explains the experimental syntheses of black-phosphorus-type As 1−x P x alloys with tunable compositions, recently reported in the literature. We investigate the phase stabilities in the ternary B-As-P system and demonstrate a high tendency for a formation of alloys in the icosahedral B 12 (As 1−x P x ) 2 structure by intermixing of As and P atoms at the diatomic chain sites. The phase diagram displays noticeable mutual solubility of the icosahedral subpnictides in each other even at room temperature as well as a closure of a pseudobinary miscibility gap around 900 K. As for pseudobinary BAs 1−x P x alloys, only a tiny amount of BAs is predicted to be able to dissolve in BP to form the BAs 1−x P x disordered alloys at elevated temperature. For example, less than 5% of BAs can dissolve in BP at T = 1000 K. The small solubility limit of BAs in BP is attributed to the thermodynamic instability of BAs with respect to B 12 As 2 and As.

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Section: Sa-sqs Modelmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

2017

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“…In addition, in such compound materials, neutron capture and ionization generation occur in the same media, allowing full absorption of secondary particles and, ideally, complete charge collection of the generated electrons and holes. Among all the candidate semiconductor materials, icosahedral boron arsenide (B 12 As 2 ) particularly is appealing for thermal neutrons detection due to its wide band-gap (3.20-3.47 eV) [2][3][4][5] and potentially good carrier-transport properties. As our first step in assessing B 12 As 2 material for radiation detection, we measured its optical properties especially the photocurrent response to a short-wavelength LED and low-temperature electrical properties.…”

Section: -2mentioning

confidence: 99%

Photocurrent response of B12As2 crystals to blue light, and its temperature- dependent electrical characterizations

et al. 2016

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With the global shortage of 3He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B12As2) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B12As2 bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W−1 and 2.47 mA ⋅ cm−2, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B12As2 bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm−2 and 7.6x105-7.7x103 Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors.

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“…Apart from being synthesized, using the chemical vapor deposition (CVD) technique for instance [27,[94][95][96][97][98], B 12 As 2 and B 12 P 2 can also be obtained from the irreversible thermal decompositions of zinc-blende boron arsenide (BAs) and boron phosphide (BP) at high temperature (T 1200 K), respectively [99][100][101]. BAs, in itself, is also of interest, as it has been predicted to have a remarkably high value of thermal conductivity (κ) at room temperature (2240 W·m…”

Section: Boron Subarsenide and Subphosphidementioning

confidence: 99%

“…Compared to the other icosahedral boron-rich solids, in particular boron carbide, having been frequently addressed in the literature [1,6,17,20,25,27,28,30,35,36,84,91,[94][95][96][108][109][110][111][112][113][114], relatively few studies have so far been made on boron subnitride [19,[115][116][117][118][119][120]. For this reason, several issues about boron subnitride, for example its stable compositions, properties, as well as the correct representation of its basic structural unit, are still inconclusive.…”

Section: Boron Subnitridementioning

confidence: 99%

Disordered Icosahedral Boron-Rich Solids: A Theoretical Study of Thermodynamic Stability and Properties

Ektarawong¹

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The cover page illustrates the crystal structure of disordered boron carbide (B 4 C), projected on the (100) r crystal plane in rhombohedral symmetry.The cover image is visualized by the VESTA package. Red and white spheres represent boron and carbon atoms, respectively.During the course of research underlying this thesis, Annop Ektarawong was enrolled in Agora Materiae, a multidisciplinary doctoral program at Linköping University, Sweden.c Annop Ektarawong Printed by LiU-Tryck 2017 AbstractThis thesis is a theoretical study of configurational disorder in icosahedral boronrich solids, in particular boron carbide, including also the development of a methodological framework for treating configurational disorder in such materials, namely superatom-special quasirandom structure (SA-SQS). In terms of its practical implementations, the SA-SQS method is demonstrated to be capable of efficiently modeling configurational disorder in icosahedral boron-rich solids, whiles the thermodynamic stability as well as the properties of the configurationally disordered icosahedral boron-rich solids, modeled from the SA-SQS method, can be directly investigated, using the density functional theory (DFT).In case of boron carbide, especially B 4 C and B 13 C 2 compositions, the SA-SQS method is used for modeling configurational disorder, arising from a high concentration of low-energy B/C substitutional defects. The results, obtained from the DFT-based calculations, demonstrate that configurational disorder of B and C atoms in boron carbide is not only thermodynamically favored at high temperature, but it also plays an important role in altering the properties of boron carbide − for example, restoration of higher rhombohedral symmetry of B 4 C, a metal-tononmetal transition and a drastic increase in the elastic moduli of B 13 C 2 . The configurational disorder can also explain large discrepancies, regarding the properties of boron carbide, between experiments and previous theoretical calculations, having been a long standing controversial issue in the field of icosahedral boronrich solids, as the calculated properties of the disordered boron carbides are found to be in qualitatively good agreement with those, observed in experiments. In order to investigate the configurational evolution of B 4 C as a function of temperature, beyond the SA-SQS level, a brute-force cluster-expansion method in combination with Monte Carlo simulations is implemented. The results demonstrate that configurational disorder in B 4 C indeed essentially takes place within the icosahedra in a way that justifies the focus on low-energy defect patterns of the superatom picture.The investigation of the thermodynamic stability of icosahedral carbon-rich iii iv boron carbides beyond the believed solubility limit of carbon (20 at.% C) demonstrates that, apart from B 4 C generally addressed in the literature, B 2.5 C represented by B 10 C p 2 (CC) is predicted to be thermodynamically stable with respect to B 4 C as well as pure boron and carbon under high pressure...

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Energy band structure and optical response function of icosahedralB12As2: A spectroscopic ellipsometry and first-principles calculational study

Cited by 24 publications

References 25 publications

First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

First-principles prediction of stabilities and instabilities of compounds and alloys in the ternary B-As-P system

Photocurrent response of B12As2 crystals to blue light, and its temperature- dependent electrical characterizations

Disordered Icosahedral Boron-Rich Solids: A Theoretical Study of Thermodynamic Stability and Properties

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