Structural evolution mechanisms of amorphous and liquid<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>As</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>Se</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>at high pressures

Properzi, L.; Santoro, Mario; Minicucci, Marco; Iesari, Fabio; Ciambezi, M.; Nataf, Lucie; Godec, Yann Le; Irifune, Tetsuo; Baudelet, F.; Cicco, Andrea Di

doi:10.1103/physrevb.93.214205

Cited by 18 publications

(12 citation statements)

References 42 publications

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“…This behavior is assigned to the slight elongation of the As—Se bond from ≈2.42 to 2.44 Å and the high disordering in the bond orientations upon increasing pressures. Even at high pressures (30 GPa), no signs of crystallization or gradual metallization were detected …”

Section: Resultscontrasting

confidence: 99%

“…In contrast, as shown in the inset of Figure , the X‐ray diffraction analysis which was conducted in the diffraction angle (2 θ ) range of 10 o –70 o reveals no intensive peaks, indicating the glassy nature of growth of the films. Studies on the crystallization processes in arsenic selenide have shown that this material prefers the amorphous nature of growth even at high pressures and temperatures . This behavior is assigned to the slight elongation of the As—Se bond from ≈2.42 to 2.44 Å and the high disordering in the bond orientations upon increasing pressures.…”

Section: Resultsmentioning

confidence: 91%

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Pseudodielectric Dispersion in As₂Se₃ Thin Films

Kayed

Qasrawi

2019

Physica Status Solidi (b)

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Herein, X‐ray diffraction, energy dispersive X‐ray spectroscopy, and spectral ellipsometry techniques are used to investigate the structural, pseudo‐optical, and pseudodielectric properties of arsenic selenide thin films. The stoichiometric films which are prepared by the thermal evaporation technique are found to prefer the amorphous nature of growth. While the pseudoabsorption coefficient spectra display strong absorption bands at 1.84, 1.81, 1.41, and 1.13 eV, the preferred pseudo‐optical transitions happen within a direct forbidden energy bandgap of 1.80 eV. In addition, the real part of the pseudodielectric spectra displays three strong resonance peaks at critical energy values of 2.33, 1.90, and 1.29 eV. Modeling of the imaginary part of the pseudodielectric constant spectra in accordance with the Drude–Lorentz approach results in the existence of six linear oscillators. The response of arsenic selenide to elliptically polarized light signals shows that the films exhibit drift mobility, free electron concentration, and plasmon frequency values in the ranges of 0.21–43.96 cm2 V−1s−1, 1.90–58.0 × 1019 cm−3, and 5.8–32.0 GHz, respectively. The optical conductivity parameters for As2Se3 film nominate it as a promising candidate for the fabrication of tunneling diodes suitable for microwaves filtering up to 32.0 GHz and as thin‐film transistors.

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Section: Resultscontrasting

confidence: 99%

Section: Resultsmentioning

confidence: 91%

Pseudodielectric Dispersion in As₂Se₃ Thin Films

Kayed

Qasrawi

2019

Physica Status Solidi (b)

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“…Polyamorphism referring to multiple amorphous states with different densities and coordination numbers but the same composition is commonly observed during the high‐pressure treatment of tetrahedrally coordinated amorphous systems such as ice, silicon, germanium, silica, germinate, and chalcogenide glasses . Ice shows a first‐order phase transformation from a low‐density amorphous (LDA) state to a high‐density amorphous (HDA) state under pressure .…”

Section: Introductionmentioning

confidence: 95%

“…Similar to ice, polyamorphic phase transformation in silicon and germanium is accompanied by a sharp volume collapse as well and their HDA phase exhibits a metallic character. In a stark contrast to these materials, the amorphous‐to‐amorphous phase transformation takes place gradually in silica, germinate, and chalcogenide glasses . Depending on the temperature and pressure conditions applied, their HDA phase can be quenchable or unquenchable to ambient pressure.…”

Section: Introductionmentioning

confidence: 99%

“…Polyamorphism 1 referring to multiple amorphous states with different densities and coordination numbers but the same composition is commonly observed during the highpressure treatment of tetrahedrally coordinated amorphous systems such as ice 2 , silicon 3-6 , germanium 7,8 , silica [9][10][11][12] , germinate 13 , and chalcogenide glasses. [14][15][16][17] Ice shows a first-order phase transformation from a low-density amorphous (LDA) state to a high-density amorphous (HDA) state under pressure. 2 Similar to ice, polyamorphic phase transformation in silicon [3][4][5][6] and germanium 7,8 is accompanied by a sharp volume collapse as well and their HDA phase exhibits a metallic character.…”

Section: Introductionmentioning

confidence: 99%

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Two successive amorphous‐to‐amorphous phase transformations in TiO₂

Durandurdu

2017

J Am Ceram Soc

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Based on constant pressure ab initio simulations, we propose, for the first time, two successive amorphous‐to‐amorphous phase transformations for TiO2. The first one is a gradual phase transformation from a low‐density amorphous phase to a high‐density amorphous phase, whereas the second one is a first‐order phase transformation from the high‐density amorphous phase to a very high‐density amorphous phase. The low‐density amorphous to high‐density amorphous phase change is irreversible, whereas the high‐density amorphous to very high‐density amorphous phase transformation is reversible. The high‐density amorphous and very high‐density amorphous phases consist of differently coordinated configurations. The sevenfold and ninefold‐coordinated arrangements formed in amorphous TiO2 under pressure are similar to the main building motif of the baddeleyite and cotunnite polymorphs of TiO2, respectively, while the eightfold‐coordinated configuration is different from the local structure of the cubic TiO2 phase. The electronic structure calculations suggest that both dense amorphous phases present a semiconducting character with a band gap energy less than that of the original low‐density amorphous phase.

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Tailoring Mid‐Gap States of Chalcogenide Glass by Pressure‐Induced Hypervalent Bonding Towards the Design of Electrical Switching Materials

et al. 2023

Adv Funct Materials

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Phase change memory (PCM) and ovonic threshold switching (OTS) materials using chalcogenide glass are essential elements in advanced 3D memory chips. The mid‐gap states, induced by the disorder and defects in the glass, are the physical mechanisms of the electrical switching behavior, while the origin of these trap states is still under debate and the medium‐range clusters that break the global octet rule, such as over‐coordinated atoms, are known to be responsible in various glass. Here, it is discovered that a large fraction of over‐coordinated clusters fails to generate mid‐gap states, which are probably caused by hypervalent bonding, a multi‐centered covalent bond participated by delocalized lone‐pair electrons. This is confirmed by the pressure‐driven simulations of amorphous GeSe models, in which it is found that octahedral motifs and hypervalent bonds prevent the over‐coordinated medium‐range clusters from providing excessive electrons. In practical applications, compatible dopants can be used to change the number of hypervalent bonds, thus controlling the number of mid‐gap states and consequently the performance of PCM and OTS materials. These results reveal the origin of mid‐gap states in chalcogenide glasses, enabling extensive control in the development of pioneering electrical switching materials.

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Structural evolution mechanisms of amorphous and liquidAs2Se3at high pressures

Cited by 18 publications

References 42 publications

Pseudodielectric Dispersion in As₂Se₃ Thin Films

Pseudodielectric Dispersion in As₂Se₃ Thin Films

Two successive amorphous‐to‐amorphous phase transformations in TiO₂

Tailoring Mid‐Gap States of Chalcogenide Glass by Pressure‐Induced Hypervalent Bonding Towards the Design of Electrical Switching Materials

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Structural evolution mechanisms of amorphous and liquidAs2Se3at high pressures

Cited by 18 publications

References 42 publications

Pseudodielectric Dispersion in As2Se3 Thin Films

Pseudodielectric Dispersion in As2Se3 Thin Films

Two successive amorphous‐to‐amorphous phase transformations in TiO2

Tailoring Mid‐Gap States of Chalcogenide Glass by Pressure‐Induced Hypervalent Bonding Towards the Design of Electrical Switching Materials

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Product

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Pseudodielectric Dispersion in As₂Se₃ Thin Films

Pseudodielectric Dispersion in As₂Se₃ Thin Films

Two successive amorphous‐to‐amorphous phase transformations in TiO₂