The Experts below are selected from a list of 21 Experts worldwide ranked by ideXlab platform
Pierre Saint-grégoire - One of the best experts on this subject based on the ideXlab platform.
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Stress-induced change of the Lifshitz point type in A2BX4 compounds
Journal of Physics: Condensed Matter, 2002Co-Authors: Igor A. Luk'yanchuk, Pierre Saint-grégoireAbstract:The high-temperature Transition P63/mmc?Pmcn in A2BX4 compounds is driven by the unique geometrical factor c/a of the hcp structure and occurs either directly for compounds with c/a?1.26 or via an intermediate incommensurate phase for compounds with c/a?1.26. We show that the prominent feature of the Lifshitz point that occurs at c/a = 1.26 is that all three Incoming Transition lines are of first order. We attribute this property to the interaction of the order parameter with the elastic degrees of freedom and classify the types of Lifshitz point that are possible in this case. We discuss the experimental properties of the Lifshitz point in A2BX4 compounds.
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Stress induced change of the Lifshitz point type in A2BX4 compounds
Ferroelectrics, 2002Co-Authors: I. Luk'yanchukj, Pierre Saint-grégoireAbstract:The high-temperature Transition P6 3 /mmc-Pmcn in A 2 BX 4 compounds is driven by the unique geometrical factor c/a of the hcp structure and occurs either directly for compounds with c/a > 1.26 or via an intermediate incommensurate phase for compounds with c/a < 1.26. We show that the prominent feature of the Lifshitz point that takes place at c/a = 1.26 is that all three Incoming Transition lines are of the first order. We attribute this property to the interaction of the order parameter with elastic degrees of freedom and classify the types of the Lifshitz point that are possible in this case. We discuss the experimental properties of the Lifshitz point in A 2 BX 4 compounds.
K. R. Hofmann - One of the best experts on this subject based on the ideXlab platform.
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Single-Electron Charging and Discharging Analyses in Ge-Nanocrystal Memories
IEEE Transactions on Electron Devices, 2011Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, M. Erenburg, Eberhard Bugiel, K. R. HofmannAbstract:The transient charging/discharging of electrons in Ge-nanocrystal (NC) memories are measured by a pump-and-probe method that allows keeping track of the number of electrons per NC. The experiments are simulated with a quantum kinetic mechanical model based on the density-functional theory, which can describe the NCs' charging state. In the transient charging, electrons are captured faster than predicted by simulations. This was attributed to the presence of defects in the NC surface, action of which is twofold: 1) The Incoming electrons are captured by NC states and are quickly thermalized down to the surface traps. 2) Those traps enlarge the spatial distribution of the confined wave functions, increasing their penetration in the tunneling oxide and the Incoming Transition rates. As for the discharging, the calculations and experiments agree until there are only few electrons left per NC. Then, the out tunneling becomes slower than predicted by calculations. The remaining electrons are confined in trap states with energies located in the NC bandgap, and they have to be thermally excited to NC states and to tunnel out to the substrate.
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Interface defect-assisted single electron charging (and discharging) dynamics in Ge nanocrystals memories
Applied Physics Letters, 2010Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, K. R. HofmannAbstract:The charging and discharging dynamics of Ge nanocrystal memories is measured and compared with a realistic quantum mechanical model that is able to reproduce qualitatively the overall device behavior. Quantitatively, the charging (discharging) dynamics is faster (slower) than predicted by calculations. To explain the discrepancies, we propose the quantum confined nanocrystal states are responsible for collecting the Incoming electrons, but some of them are captured by defects in the nanocrystal surface. The potential created by the filled defects modify the spatial distribution of the nanocrystal wave functions, enhancing their penetration in the tunneling oxide and increasing the Incoming Transition rates. In the discharging process, the electrons confined in the nanocrystal states escape initially, while the ones in the defects have to be thermally excited to the nanocrystals states in order to tunnel out, slowing down the escape of the last few electrons.
J. S. De Sousa - One of the best experts on this subject based on the ideXlab platform.
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Single-Electron Charging and Discharging Analyses in Ge-Nanocrystal Memories
IEEE Transactions on Electron Devices, 2011Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, M. Erenburg, Eberhard Bugiel, K. R. HofmannAbstract:The transient charging/discharging of electrons in Ge-nanocrystal (NC) memories are measured by a pump-and-probe method that allows keeping track of the number of electrons per NC. The experiments are simulated with a quantum kinetic mechanical model based on the density-functional theory, which can describe the NCs' charging state. In the transient charging, electrons are captured faster than predicted by simulations. This was attributed to the presence of defects in the NC surface, action of which is twofold: 1) The Incoming electrons are captured by NC states and are quickly thermalized down to the surface traps. 2) Those traps enlarge the spatial distribution of the confined wave functions, increasing their penetration in the tunneling oxide and the Incoming Transition rates. As for the discharging, the calculations and experiments agree until there are only few electrons left per NC. Then, the out tunneling becomes slower than predicted by calculations. The remaining electrons are confined in trap states with energies located in the NC bandgap, and they have to be thermally excited to NC states and to tunnel out to the substrate.
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Interface defect-assisted single electron charging (and discharging) dynamics in Ge nanocrystals memories
Applied Physics Letters, 2010Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, K. R. HofmannAbstract:The charging and discharging dynamics of Ge nanocrystal memories is measured and compared with a realistic quantum mechanical model that is able to reproduce qualitatively the overall device behavior. Quantitatively, the charging (discharging) dynamics is faster (slower) than predicted by calculations. To explain the discrepancies, we propose the quantum confined nanocrystal states are responsible for collecting the Incoming electrons, but some of them are captured by defects in the nanocrystal surface. The potential created by the filled defects modify the spatial distribution of the nanocrystal wave functions, enhancing their penetration in the tunneling oxide and increasing the Incoming Transition rates. In the discharging process, the electrons confined in the nanocrystal states escape initially, while the ones in the defects have to be thermally excited to the nanocrystals states in order to tunnel out, slowing down the escape of the last few electrons.
R. Peibst - One of the best experts on this subject based on the ideXlab platform.
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Single-Electron Charging and Discharging Analyses in Ge-Nanocrystal Memories
IEEE Transactions on Electron Devices, 2011Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, M. Erenburg, Eberhard Bugiel, K. R. HofmannAbstract:The transient charging/discharging of electrons in Ge-nanocrystal (NC) memories are measured by a pump-and-probe method that allows keeping track of the number of electrons per NC. The experiments are simulated with a quantum kinetic mechanical model based on the density-functional theory, which can describe the NCs' charging state. In the transient charging, electrons are captured faster than predicted by simulations. This was attributed to the presence of defects in the NC surface, action of which is twofold: 1) The Incoming electrons are captured by NC states and are quickly thermalized down to the surface traps. 2) Those traps enlarge the spatial distribution of the confined wave functions, increasing their penetration in the tunneling oxide and the Incoming Transition rates. As for the discharging, the calculations and experiments agree until there are only few electrons left per NC. Then, the out tunneling becomes slower than predicted by calculations. The remaining electrons are confined in trap states with energies located in the NC bandgap, and they have to be thermally excited to NC states and to tunnel out to the substrate.
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Interface defect-assisted single electron charging (and discharging) dynamics in Ge nanocrystals memories
Applied Physics Letters, 2010Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, K. R. HofmannAbstract:The charging and discharging dynamics of Ge nanocrystal memories is measured and compared with a realistic quantum mechanical model that is able to reproduce qualitatively the overall device behavior. Quantitatively, the charging (discharging) dynamics is faster (slower) than predicted by calculations. To explain the discrepancies, we propose the quantum confined nanocrystal states are responsible for collecting the Incoming electrons, but some of them are captured by defects in the nanocrystal surface. The potential created by the filled defects modify the spatial distribution of the nanocrystal wave functions, enhancing their penetration in the tunneling oxide and increasing the Incoming Transition rates. In the discharging process, the electrons confined in the nanocrystal states escape initially, while the ones in the defects have to be thermally excited to the nanocrystals states in order to tunnel out, slowing down the escape of the last few electrons.
Gil A. Farias - One of the best experts on this subject based on the ideXlab platform.
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Single-Electron Charging and Discharging Analyses in Ge-Nanocrystal Memories
IEEE Transactions on Electron Devices, 2011Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, M. Erenburg, Eberhard Bugiel, K. R. HofmannAbstract:The transient charging/discharging of electrons in Ge-nanocrystal (NC) memories are measured by a pump-and-probe method that allows keeping track of the number of electrons per NC. The experiments are simulated with a quantum kinetic mechanical model based on the density-functional theory, which can describe the NCs' charging state. In the transient charging, electrons are captured faster than predicted by simulations. This was attributed to the presence of defects in the NC surface, action of which is twofold: 1) The Incoming electrons are captured by NC states and are quickly thermalized down to the surface traps. 2) Those traps enlarge the spatial distribution of the confined wave functions, increasing their penetration in the tunneling oxide and the Incoming Transition rates. As for the discharging, the calculations and experiments agree until there are only few electrons left per NC. Then, the out tunneling becomes slower than predicted by calculations. The remaining electrons are confined in trap states with energies located in the NC bandgap, and they have to be thermally excited to NC states and to tunnel out to the substrate.
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Interface defect-assisted single electron charging (and discharging) dynamics in Ge nanocrystals memories
Applied Physics Letters, 2010Co-Authors: J. S. De Sousa, R. Peibst, Gil A. Farias, Jean-pierre Leburton, K. R. HofmannAbstract:The charging and discharging dynamics of Ge nanocrystal memories is measured and compared with a realistic quantum mechanical model that is able to reproduce qualitatively the overall device behavior. Quantitatively, the charging (discharging) dynamics is faster (slower) than predicted by calculations. To explain the discrepancies, we propose the quantum confined nanocrystal states are responsible for collecting the Incoming electrons, but some of them are captured by defects in the nanocrystal surface. The potential created by the filled defects modify the spatial distribution of the nanocrystal wave functions, enhancing their penetration in the tunneling oxide and increasing the Incoming Transition rates. In the discharging process, the electrons confined in the nanocrystal states escape initially, while the ones in the defects have to be thermally excited to the nanocrystals states in order to tunnel out, slowing down the escape of the last few electrons.
