The Experts below are selected from a list of 255 Experts worldwide ranked by ideXlab platform

J P Itie - One of the best experts on this subject based on the ideXlab platform.

  • pressure stability and low compressibility of intercalated cagelike materials the case of silicon clathrates
    Physical Review B, 2002
    Co-Authors: A Sanmiguel, X Blase, P Melinon, E Reny, Damien Connetable, F Tournus, Shoji Yamanaka, J P Itie
    Abstract:

    We study the behavior under pressure (up to 35 GPa) of intercalated silicon clathrates, combining x-ray diffraction experiments and ab initio calculations. We show that endohedral doping does not introduce a strong modification of the compressibility of the empty clathrate network and that in particular cases can raise it to values equivalent to the one of the silicon Diamond Phase. Intercalation can also prevent the collapse of the cage structure up to pressures at least 3 times higher than in the empty clathrate. Further we find that the stability of all studied silicon clathrate networks as well as stressed silicon Diamond is limited to average Si-Si interatomic distances higher than 2.30 Angstrom.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the b-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be 90 6 5 GPa, that is, only 8 6 5% smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the $\ensuremath{\beta}$-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be $90\ifmmode\pm\else\textpm\fi{}5\mathrm{GPa}$, that is, only $(8\ifmmode\pm\else\textpm\fi{}5)%$ smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.

Richard D Schaller - One of the best experts on this subject based on the ideXlab platform.

  • silicon nanocrystals at elevated temperatures retention of photoluminescence and Diamond silicon to β silicon carbide Phase transition
    ACS Nano, 2014
    Co-Authors: Clare E Rowland, Daniel C Hannah, Jihua Yang, Arnaud Demortiere, Vitali B Prakapenka, R E Cook, Uwe Kortshagen, Richard D Schaller
    Abstract:

    We report the photoluminescence (PL) properties of colloidal Si nanocrystals (NCs) up to 800 K and observe PL retention on par with core/shell structures of other compositions. These alkane-terminated Si NCs even emit at temperatures well above previously reported melting points for oxide-embedded particles. Using selected area electron diffraction (SAED), powder X-ray diffraction (XRD), liquid drop theory, and molecular dynamics (MD) simulations, we show that melting does not play a role at the temperatures explored experimentally in PL, and we observe a Phase change to β-SiC in the presence of an electron beam. Loss of diffraction peaks (melting) with recovery of Diamond-Phase silicon upon cooling is observed under inert atmosphere by XRD. We further show that surface passivation by covalently bound ligands endures the experimental temperatures. These findings point to covalently bound organic ligands as a route to the development of NCs for use in high temperature applications, including concentrated solar cells and electrical lighting.

  • on the origin of photoluminescence in silicon nanocrystals pressure dependent structural and optical studies
    Nano Letters, 2012
    Co-Authors: Daniel C Hannah, Jihua Yang, Paul Podsiadlo, Maria K Y Chan, Arnaud Demortiere, David J Gosztola, Vitali B Prakapenka, George C Schatz, Uwe R Kortshagen, Richard D Schaller
    Abstract:

    A lack of consensus persists regarding the origin of photoluminescence in silicon nanocrystals. Here we report pressure-dependences of X-ray diffraction and photoluminescence from alkane-terminated colloidal particles. We determine the Diamond-Phase bulk modulus, observe multiple Phase transitions, and importantly find a systematic photoluminescence red shift that matches the Xconduction-to-Γvalence transition of bulk crystalline silicon. These results, reinforced by calculations, suggest that the efficient photoluminescence, frequently attributed to defects, arises instead from core-states that remain highly indirect despite quantum confinement.

A Sanmiguel - One of the best experts on this subject based on the ideXlab platform.

  • pressure stability and low compressibility of intercalated cagelike materials the case of silicon clathrates
    Physical Review B, 2002
    Co-Authors: A Sanmiguel, X Blase, P Melinon, E Reny, Damien Connetable, F Tournus, Shoji Yamanaka, J P Itie
    Abstract:

    We study the behavior under pressure (up to 35 GPa) of intercalated silicon clathrates, combining x-ray diffraction experiments and ab initio calculations. We show that endohedral doping does not introduce a strong modification of the compressibility of the empty clathrate network and that in particular cases can raise it to values equivalent to the one of the silicon Diamond Phase. Intercalation can also prevent the collapse of the cage structure up to pressures at least 3 times higher than in the empty clathrate. Further we find that the stability of all studied silicon clathrate networks as well as stressed silicon Diamond is limited to average Si-Si interatomic distances higher than 2.30 Angstrom.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the b-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be 90 6 5 GPa, that is, only 8 6 5% smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the $\ensuremath{\beta}$-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be $90\ifmmode\pm\else\textpm\fi{}5\mathrm{GPa}$, that is, only $(8\ifmmode\pm\else\textpm\fi{}5)%$ smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.

D Zhou - One of the best experts on this subject based on the ideXlab platform.

  • synthesis of nanocrystalline Diamond thin films from an ar ch4 microwave plasma
    Journal of Applied Physics, 1998
    Co-Authors: D Zhou, A R Krauss, Lu Chang Qin, T G Mccauley, D M Gruen
    Abstract:

    Nanocrystalline Diamond thin films have been synthesized in an Ar–CH4 microwave discharge, without the addition of molecular hydrogen. X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy characterizations show that the films consist of a pure crystalline Diamond Phase with very small grain sizes ranging from 3 to 20 nm. Atomic force microscopy analysis demonstrates that the surfaces of the nanocrystalline Diamond films remain smooth independent of the film thicknesses. Furthermore, the reactant gas pressure, which strongly affects the concentration of C2 dimer in the Ar–CH4 plasma as well as the growth rate of the films, has been found to be a key parameter for the nanocrystalline Diamond thin film depositions.

  • synthesis and electron field emission of nanocrystalline Diamond thin films grown from n2 ch4 microwave plasmas
    Journal of Applied Physics, 1997
    Co-Authors: D Zhou, A R Krauss, Lu Chang Qin, T G Mccauley, D M Gruen, T D Corrigan, R P H Chang, Hubert Gnaser
    Abstract:

    Nanocrystalline Diamond films have been synthesized by microwave plasma enhanced chemical vapor deposition using N2/CH4 as the reactant gas without additional H2. The nanocrystalline Diamond Phase has been identified by x-ray diffraction and transmission electron microscopy analyses. High resolution secondary ion mass spectroscopy has been employed to measure incorporated nitrogen concentrations up to 8×1020 atoms/cm3. Electron field emission measurements give an onset field as low as 3.2 V/μm. The effect of the incorporated nitrogen on the field emission characteristics of the nanocrystalline films is discussed.

X Blase - One of the best experts on this subject based on the ideXlab platform.

  • pressure stability and low compressibility of intercalated cagelike materials the case of silicon clathrates
    Physical Review B, 2002
    Co-Authors: A Sanmiguel, X Blase, P Melinon, E Reny, Damien Connetable, F Tournus, Shoji Yamanaka, J P Itie
    Abstract:

    We study the behavior under pressure (up to 35 GPa) of intercalated silicon clathrates, combining x-ray diffraction experiments and ab initio calculations. We show that endohedral doping does not introduce a strong modification of the compressibility of the empty clathrate network and that in particular cases can raise it to values equivalent to the one of the silicon Diamond Phase. Intercalation can also prevent the collapse of the cage structure up to pressures at least 3 times higher than in the empty clathrate. Further we find that the stability of all studied silicon clathrate networks as well as stressed silicon Diamond is limited to average Si-Si interatomic distances higher than 2.30 Angstrom.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the b-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be 90 6 5 GPa, that is, only 8 6 5% smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.

  • high pressure behavior of silicon clathrates a new class of low compressibility materials
    Physical Review Letters, 1999
    Co-Authors: A Sanmiguel, Christian Cros, P Keghelian, X Blase, P Melinon, A Perez, J P Itie, A Polian, E Reny, M Pouchard
    Abstract:

    The high pressure evolution of silicon clathrates is studied at room temperature by x-ray diffraction up to 15 GPa. Remarkably, no transition towards the Diamond structure is observed and the clathrate Phase transforms directly into the $\ensuremath{\beta}$-tin metallic Phase at 11 GPa. Further, the bulk modulus is found to be $90\ifmmode\pm\else\textpm\fi{}5\mathrm{GPa}$, that is, only $(8\ifmmode\pm\else\textpm\fi{}5)%$ smaller than the one of the Diamond Phase. These results are in good agreement with ab initio calculations which predict further that carbon clathrates, if synthesized, should be less compressible than cubic BN.