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Allotropy

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Timothy A. Strobel – One of the best experts on this subject based on the ideXlab platform.

  • Exploring silicon Allotropy and chemistry by high pressure – high temperature conditions
    Journal of Physics: Conference Series, 2017
    Co-Authors: Oleksandr O. Kurakevych, Duck Young Kim, Timothy A. Strobel, Yann Le Godec, Wilson A. Crichton, Jérémy Guignard
    Abstract:

    Silicon is the second abundant element, after oxygen, in the earth crust. It is essential for today’s electronics because of its ability to show various electronic behaviors that allow covering the numerous fields of cutting-edge applications. Moreover, silicon is not a pollutant and, therefore, is an ideal candidate to replace the actual materials in photovoltaics, like compounds based on the arsenic and heavy metals. It has not replaced them so far because Si is an indirect gap semisemiconductor and cannot absorb directly the solar photons without thermal agitations of crystal lattice (phonons). This puts it apart from the next-generation applications (light diode, high-performance transistor). That justifies the attempts to create silicon materials with direct gap that can absorb and emit light. Our recent high-pressure studies of the chemical interaction and phase transformations in the Na-Si system, revealed a number of interesting routes to new and known silicon compounds and allotropes. The pressure-temperature range of their formation is suitable for large-volume synthesis and future industrial scaling. The variety of properties observed (e.g. quasi-direct bandgap of open-framework allotrope Si24) allows us to suggest future industrial applications.

  • Silicon Allotropy and Chemistry at Extreme Conditions
    Energy Procedia, 2016
    Co-Authors: Oleksandr O. Kurakevych, Yann Le Godec, Wilson A. Crichton, Timothy A. Strobel
    Abstract:

    Abstract Silicon is essential for today’s electronics because of its ability to show various electronic behaviors that are relevant to numerous fields of cutting-edge applications. It is not a pollutant and, therefore, an ideal candidate to replace the actual materials in photovoltaics, such as compounds based on the arsenic and heavy metals. However, conventional diamond-like Si is an indirect gap semisemiconductor and cannot absorb solar photons directly. This justifies intensive theoretical and experimental research for the direct-bandgap forms of silicon. Our recent high-pressure studies of the chemical interaction and phase transformations in the Na-Si system, revealed a number of interesting routes to new and known silicon compounds and allotropes. The pressure-temperature range of their formation is suitable for large-volume synthesis and future industrial scaling. The variety of properties observed (e.g. quasi-direct bandgap of open-framework allotrope Si 24 ) allows us to suggest future applications.

  • Synthesis of an open-framework allotrope of silicon
    Nature Materials, 2015
    Co-Authors: Duck Young Kim, Stevce Stefanoski, Oleksandr O. Kurakevych, Timothy A. Strobel
    Abstract:

    Silicon is ubiquitous in contemporary technology. The most stable form of silicon at ambient conditions takes on the structure of diamond (cF8, d -Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies^ 1 , 2 , 3 , 4 . Here, we report the formation of a new orthorhombic allotrope of silicon, Si_24, using a novel two-step synthesis methodology. First, a Na_4Si_24 precursor was synthesized at high pressure^ 5 ; second, sodium was removed from the precursor by a thermal ‘degassing’ process. The Cmcm structure of Si_24, which has 24 Si atoms per unit cell ( o C24), contains open channels along the crystallographic a -axis that are formed from six- and eight-membered sp ^3 silicon rings. This new allotrope possesses a quasidirect bandgap near 1.3 eV. Our combined experimental/theoretical study expands the known Allotropy for element fourteen and the unique high-pressure precursor synthesis methodology demonstrates the potential for new materials with desirable properties. A new orthorhombic allotrope of silicon, Si_24, is demonstrated using a two-step synthesis. Its structure contains open channels and it possesses a quasidirect bandgap near 1.3 eV.

Jill A. Miwa – One of the best experts on this subject based on the ideXlab platform.

  • Pnictogens Allotropy and Phase Transformation during van der Waals Growth
    Nano letters, 2020
    Co-Authors: Matthieu Fortin-deschênes, Hannes Zschiesche, Tevfik Onur Menteş, Andrea Locatelli, Robert M. Jacobberger, Francesca Genuzio, Maureen J. Lagos, Deepnarayan Biswas, Chris Jozwiak, Jill A. Miwa
    Abstract:

    With their ns2 np3 valence electronic configuration, pnictogens are the only system to crystallize in layered van der Waals (vdW) and quasi-vdW structures throughout the group. Light pnictogens crystallize in the A17 phase, and bulk heavier elements prefer the A7 phase. Herein, we demonstrate that the A17 of heavy pnictogens can be stabilized in antimonene grown on weakly interacting surfaces and that it undergoes a spontaneous thickness-driven transformation to the stable A7 phase. At a critical thickness of ∼4 nm, A17 antimony transforms from AB- to AA-stacked α-antimonene by a diffusionless shuffle transition followed by a gradual relaxation to the A7 phase. Furthermore, the competition between A7- and A17-like bonding affects the electronic structure of the intermediate phase. These results highlight the critical role of the atomic structure and substrate-layer interactions in shaping the stability and properties of layered materials, thus enabling a new degree of freedom to engineer their performance.

Oleksandr O. Kurakevych – One of the best experts on this subject based on the ideXlab platform.

  • Exploring silicon Allotropy and chemistry by high pressure – high temperature conditions
    Journal of Physics: Conference Series, 2017
    Co-Authors: Oleksandr O. Kurakevych, Duck Young Kim, Timothy A. Strobel, Yann Le Godec, Wilson A. Crichton, Jérémy Guignard
    Abstract:

    Silicon is the second abundant element, after oxygen, in the earth crust. It is essential for today’s electronics because of its ability to show various electronic behaviors that allow covering the numerous fields of cutting-edge applications. Moreover, silicon is not a pollutant and, therefore, is an ideal candidate to replace the actual materials in photovoltaics, like compounds based on the arsenic and heavy metals. It has not replaced them so far because Si is an indirect gap semiconductor and cannot absorb directly the solar photons without thermal agitations of crystal lattice (phonons). This puts it apart from the next-generation applications (light diode, high-performance transistor). That justifies the attempts to create silicon materials with direct gap that can absorb and emit light. Our recent high-pressure studies of the chemical interaction and phase transformations in the Na-Si system, revealed a number of interesting routes to new and known silicon compounds and allotropes. The pressure-temperature range of their formation is suitable for large-volume synthesis and future industrial scaling. The variety of properties observed (e.g. quasi-direct bandgap of open-framework allotrope Si24) allows us to suggest future industrial applications.

  • Silicon Allotropy and Chemistry at Extreme Conditions
    Energy Procedia, 2016
    Co-Authors: Oleksandr O. Kurakevych, Yann Le Godec, Wilson A. Crichton, Timothy A. Strobel
    Abstract:

    Abstract Silicon is essential for today’s electronics because of its ability to show various electronic behaviors that are relevant to numerous fields of cutting-edge applications. It is not a pollutant and, therefore, an ideal candidate to replace the actual materials in photovoltaics, such as compounds based on the arsenic and heavy metals. However, conventional diamond-like Si is an indirect gap semiconductor and cannot absorb solar photons directly. This justifies intensive theoretical and experimental research for the direct-bandgap forms of silicon. Our recent high-pressure studies of the chemical interaction and phase transformations in the Na-Si system, revealed a number of interesting routes to new and known silicon compounds and allotropes. The pressure-temperature range of their formation is suitable for large-volume synthesis and future industrial scaling. The variety of properties observed (e.g. quasi-direct bandgap of open-framework allotrope Si 24 ) allows us to suggest future applications.

  • Synthesis of an open-framework allotrope of silicon
    Nature Materials, 2015
    Co-Authors: Duck Young Kim, Stevce Stefanoski, Oleksandr O. Kurakevych, Timothy A. Strobel
    Abstract:

    Silicon is ubiquitous in contemporary technology. The most stable form of silicon at ambient conditions takes on the structure of diamond (cF8, d -Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies^ 1 , 2 , 3 , 4 . Here, we report the formation of a new orthorhombic allotrope of silicon, Si_24, using a novel two-step synthesis methodology. First, a Na_4Si_24 precursor was synthesized at high pressure^ 5 ; second, sodium was removed from the precursor by a thermal ‘degassing’ process. The Cmcm structure of Si_24, which has 24 Si atoms per unit cell ( o C24), contains open channels along the crystallographic a -axis that are formed from six- and eight-membered sp ^3 silicon rings. This new allotrope possesses a quasidirect bandgap near 1.3 eV. Our combined experimental/theoretical study expands the known Allotropy for element fourteen and the unique high-pressure precursor synthesis methodology demonstrates the potential for new materials with desirable properties. A new orthorhombic allotrope of silicon, Si_24, is demonstrated using a two-step synthesis. Its structure contains open channels and it possesses a quasidirect bandgap near 1.3 eV.

Matthieu Fortin-deschênes – One of the best experts on this subject based on the ideXlab platform.

  • Pnictogens Allotropy and Phase Transformation during van der Waals Growth
    Nano letters, 2020
    Co-Authors: Matthieu Fortin-deschênes, Hannes Zschiesche, Tevfik Onur Menteş, Andrea Locatelli, Robert M. Jacobberger, Francesca Genuzio, Maureen J. Lagos, Deepnarayan Biswas, Chris Jozwiak, Jill A. Miwa
    Abstract:

    With their ns2 np3 valence electronic configuration, pnictogens are the only system to crystallize in layered van der Waals (vdW) and quasi-vdW structures throughout the group. Light pnictogens crystallize in the A17 phase, and bulk heavier elements prefer the A7 phase. Herein, we demonstrate that the A17 of heavy pnictogens can be stabilized in antimonene grown on weakly interacting surfaces and that it undergoes a spontaneous thickness-driven transformation to the stable A7 phase. At a critical thickness of ∼4 nm, A17 antimony transforms from AB- to AA-stacked α-antimonene by a diffusionless shuffle transition followed by a gradual relaxation to the A7 phase. Furthermore, the competition between A7- and A17-like bonding affects the electronic structure of the intermediate phase. These results highlight the critical role of the atomic structure and substrate-layer interactions in shaping the stability and properties of layered materials, thus enabling a new degree of freedom to engineer their performance.

Duck Young Kim – One of the best experts on this subject based on the ideXlab platform.

  • Exploring silicon Allotropy and chemistry by high pressure – high temperature conditions
    Journal of Physics: Conference Series, 2017
    Co-Authors: Oleksandr O. Kurakevych, Duck Young Kim, Timothy A. Strobel, Yann Le Godec, Wilson A. Crichton, Jérémy Guignard
    Abstract:

    Silicon is the second abundant element, after oxygen, in the earth crust. It is essential for today’s electronics because of its ability to show various electronic behaviors that allow covering the numerous fields of cutting-edge applications. Moreover, silicon is not a pollutant and, therefore, is an ideal candidate to replace the actual materials in photovoltaics, like compounds based on the arsenic and heavy metals. It has not replaced them so far because Si is an indirect gap semiconductor and cannot absorb directly the solar photons without thermal agitations of crystal lattice (phonons). This puts it apart from the next-generation applications (light diode, high-performance transistor). That justifies the attempts to create silicon materials with direct gap that can absorb and emit light. Our recent high-pressure studies of the chemical interaction and phase transformations in the Na-Si system, revealed a number of interesting routes to new and known silicon compounds and allotropes. The pressure-temperature range of their formation is suitable for large-volume synthesis and future industrial scaling. The variety of properties observed (e.g. quasi-direct bandgap of open-framework allotrope Si24) allows us to suggest future industrial applications.

  • Synthesis of an open-framework allotrope of silicon
    Nature Materials, 2015
    Co-Authors: Duck Young Kim, Stevce Stefanoski, Oleksandr O. Kurakevych, Timothy A. Strobel
    Abstract:

    Silicon is ubiquitous in contemporary technology. The most stable form of silicon at ambient conditions takes on the structure of diamond (cF8, d -Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies^ 1 , 2 , 3 , 4 . Here, we report the formation of a new orthorhombic allotrope of silicon, Si_24, using a novel two-step synthesis methodology. First, a Na_4Si_24 precursor was synthesized at high pressure^ 5 ; second, sodium was removed from the precursor by a thermal ‘degassing’ process. The Cmcm structure of Si_24, which has 24 Si atoms per unit cell ( o C24), contains open channels along the crystallographic a -axis that are formed from six- and eight-membered sp ^3 silicon rings. This new allotrope possesses a quasidirect bandgap near 1.3 eV. Our combined experimental/theoretical study expands the known Allotropy for element fourteen and the unique high-pressure precursor synthesis methodology demonstrates the potential for new materials with desirable properties. A new orthorhombic allotrope of silicon, Si_24, is demonstrated using a two-step synthesis. Its structure contains open channels and it possesses a quasidirect bandgap near 1.3 eV.

  • Synthesis of an open-framework allotrope of silicon
    Nature Materials, 2015
    Co-Authors: Duck Young Kim, Stevce Stefanoski, Oleksandr O. Kurakevych, Timothy A. Strobel
    Abstract:

    Silicon is ubiquitous in contemporary technology. The most stable form of ​silicon at ambient conditions takes on the structure of diamond (cF8, d-Si) and is an indirect bandgap semiconductor, which prevents it from being considered as a next-generation platform for semiconductor technologies1, 2, 3, 4. Here, we report the formation of a new orthorhombic allotrope of ​silicon, Si24, using a novel two-step synthesis methodology. First, a Na4Si24 precursor was synthesized at high pressure5; second, sodium was removed from the precursor by a thermal ‘degassing’ process. The Cmcm structure of Si24, which has 24 Si atoms per unit cell (oC24), contains open channels along the crystallographic a-axis that are formed from six- and eight-membered sp3 silicon rings. This new allotrope possesses a quasidirect bandgap near 1.3 eV. Our combined experimental/theoretical study expands the known Allotropy for element fourteen and the unique high-pressure precursor synthesis methodology demonstrates the potential for new materials with desirable properties.