X‐ray diffraction study of amorphous phase of BaSi<sub>2</sub> under high pressure

Nishii, Takaya; Mizuno, Takafumi; Mori, Yojiro; Takarabe, Kenichi; Imai, Motoharu; Kohara, Shinji

doi:10.1002/pssb.200672563

Cited by 14 publications

(10 citation statements)

References 5 publications

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“…The observed transformation of highdensity amorphous Rb 6.15 Si 46 to a low-density polyamorph during decompression indicates that the HDA-LDA transition observed for elemental a-Si extends into the binary Si-Rb alloy system and presumably into other semiconductor-metal alloy as, for example, in the Zintl phase BaSi 2 where pressure-induced amorphization has been observed to occur at around 13 GPa. 70 This observation provides a useful link between studies of PIA and polyamorphism within various compound metalloid systems such as Al-Ge, Ga-Sb, etc. 71…”

Section: ͒mentioning

confidence: 85%

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

et al. 2009

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The type-I clathrate Rb 6.15 Si 46 with partly empty cage sites has been studied up to 36 GPa using Raman spectroscopy, synchrotron x-ray diffraction in diamond-anvil cells, and ab initio total-energy and latticedynamics calculations. A first phase transition is observed at 13Ϯ 1 GPa and a "volume collapse" transition within the clathrate structure is then observed at 24Ϯ 1 GPa. Pressure-induced amorphization into a highdensity amorphous ͑HDA͒ state occurs above P =33Ϯ 1 GPa. The HDA form transforms into a low-density amorphous polymorph during decompression. During the compression study using angle dispersive synchrotron x-ray diffraction techniques we measured bulk modulus parameters for rocksalt-structured TaO, included adventitiously in the clathrate sample ͓K 0 = 293͑3͒ GPa and K 0 Ј=5.4͑3͔͒.

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Section: ͒mentioning

confidence: 85%

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

et al. 2009

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“… 7 , 8 The orthorhombic BaSi 2 is stable in the ambient condition, 9 exhibits an unintentionally n-type conductivity, 10 and possesses a suitable band gap ( E g = ∼1.3 eV) for solar energy conversion. 11 − 14 In addition, its great potential also stems from attractive optical and electrical properties, i.e., a high light absorption coefficient (α) reaching 10 5 cm –1 for photon energy hv > 1.5 eV, 15 , 16 a long minority carrier lifetime τ (∼10–27 μs), 17 − 19 and essentially elemental abundance and nontoxicity. Theoretically, the attainable conversion efficiency (η) of BaSi 2 homojunction solar cells is up to 25%.…”

Section: Introductionmentioning

confidence: 99%

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Tian

Vismara

Doorene

et al. 2018

ACS Appl. Energy Mater.

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Barium disilicide (BaSi2) has been regarded as a promising absorber material for high-efficiency thin-film solar cells. However, it has confronted issues related to material synthesis and quality control. Here, we fabricate BaSi2 thin films via an industrially applicable sputtering process and uncovered the mechanism of structure transformation. Polycrystalline BaSi2 thin films are obtained through the sputtering process followed by a postannealing treatment. The crystalline quality and phase composition of sputtered BaSi2 are characterized by Raman spectroscopy and X-ray diffraction (XRD). A higher annealing temperature can promote crystallization of BaSi2, but also causes an intensive surface oxidation and BaSi2/SiO2 interfacial diffusion. As a consequence, an inhomogeneous and layered structure of BaSi2 is revealed by Auger electron spectroscopy (AES) and transmission electron microscopy (TEM). The thick oxide layer in such an inhomogeneous structure hinders further both optical and electrical characterizations of sputtered BaSi2. The structural transformation process of sputtered BaSi2 films then is studied by the Raman depth-profiling method, and all of the above observations come to an oxidation-induced structure transformation mechanism. It interprets interfacial phenomena including surface oxidation and BaSi2/SiO2 interdiffusion, which lead to the inhomogeneous and layered structure of sputtered BaSi2. The mechanism can also be extended to epitaxial and evaporated BaSi2 films. In addition, a glimpse toward future developments in both material and device levels is presented. Such fundamental knowledge on structural transformations and complex interfacial activities is significant for further quality control and interface engineering on BaSi2 films toward high-efficiency solar cells.

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“…Although it is thermodynamically stable, formation of the LiSi structure is kinetically impeded relative to phases such as Li 12 Si 7 : only high-P,T synthesis could demonstrate the existence of this phase. Recent studies have investigated the high pressure behaviour of Zintl phases such as BaSi 2 that contain corrugated sheets of the silicide polyanion with three-fold coordinated silicon species [205]: the crystalline structure is lost at high pressure indicating further crystalline phases existing at high density. Pressureinduced amorphisation also occurs for NaSi that is likely accompanied by loss of Na from the structure.…”

Section: Clathrates and New"light Element" Solidsmentioning

confidence: 99%

Solid-State and Materials-Chemistry at High Pressure

McMillan¹

2012

Scottish Graduate Series

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Solid state chemistry is concerned with understanding and developing the structures, phase relationships, properties and synthesis of crystalline and amorphous elements and compounds as well as composite materials. High pressure science began within physics and physical chemistry as new techniques were applied to increase pressures into ranges where significant changes in structures and physical properties could be observed. High-P,T studies immediately led to major advances in mineralogy, solid state chemistry and materials research that continue to be developed today.

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X‐ray diffraction study of amorphous phase of BaSi₂ under high pressure

Cited by 14 publications

References 5 publications

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Solid-State and Materials-Chemistry at High Pressure

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X‐ray diffraction study of amorphous phase of BaSi2 under high pressure

Cited by 14 publications

References 5 publications

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

High-pressure phase transformations, pressure-induced amorphization, and polyamorphic transition of the clathrateRb6.15Si46

Oxidation-Induced Structure Transformation: Thin-Film Synthesis and Interface Investigations of Barium Disilicide toward Potential Photovoltaic Applications

Solid-State and Materials-Chemistry at High Pressure

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X‐ray diffraction study of amorphous phase of BaSi₂ under high pressure