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Atomic Plane
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Alexander A. Balandin – One of the best experts on this subject based on the ideXlab platform.
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phonons and thermal transport in graphene and graphene based materials
Reports on Progress in Physics, 2017Co-Authors: Denis L. Nika, Alexander A. BalandinAbstract:: A discovery of the unusual thermal properties of graphene stimulated experimental, theoretical and computational research directed at understanding phonon transport and thermal conduction in two-dimensional material systems. We provide a critical review of recent results in the graphene thermal field focusing on phonon dispersion, specific heat, thermal conductivity, and comparison of different models and computational approaches. The correlation between the phonon spectrum in graphene-based materials and the heat conduction properties is analyzed in details. The effects of the Atomic Plane rotations in bilayer graphene, isotope engineering, and relative contributions of different phonon dispersion branches are discussed. For readers’ convenience, the summaries of main experimental and theoretical results on thermal conductivity as well as phonon mode contributions to thermal transport are provided in the form of comprehensive annotated tables.
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engineering of the thermodynamic properties of bilayer graphene by Atomic Plane rotations the role of the out of Plane phonons
Nanoscale, 2015Co-Authors: Denis L. Nika, Alexandr I. Cocemasov, Alexander A. BalandinAbstract:We investigated theoretically the specific heat of graphene, bilayer graphene and twisted bilayer graphene taking into account the exact phonon dispersion and density of states for each polarization branch. It is shown that contrary to a conventional belief the dispersion of the out-of-Plane acoustic phonons – referred to as ZA phonons – deviates strongly from a parabolic law starting from the frequencies as low as ∼100 cm−1. This leads to the frequency-dependent ZA phonon density of states and the breakdown of the linear dependence of the specific heat on temperature T. We established that ZA phonons determine the specific heat for T ≤ 200 K while contributions from both in-Plane and out-of-Plane acoustic phonons are dominant for 200 K ≤ T ≤ 500 K. In the high-temperature limit, T > 1000 K, the optical and acoustic phonons contribute approximately equally to the specific heat. The Debye temperature for graphene and twisted bilayer graphene was calculated to be around ∼1861–1864 K. Our results suggest that the thermodynamic properties of materials such as bilayer graphene can be controlled at the Atomic scale by rotation of the sp2-carbon Planes.
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Specific heat of twisted bilayer graphene: Engineering phonons by Atomic Plane rotations
Applied Physics Letters, 2014Co-Authors: Denis L. Nika, Alexandr I. Cocemasov, Alexander A. BalandinAbstract:We have studied the phonon specific heat in single-layer, bilayer, and twisted bilayer graphene. The calculations were performed using the Born-von Karman model of lattice dynamics for intralayer Atomic interactions and spherically symmetric interAtomic potential for interlayer interactions. We found that at temperature T
Denis L. Nika – One of the best experts on this subject based on the ideXlab platform.
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phonons and thermal transport in graphene and graphene based materials
Reports on Progress in Physics, 2017Co-Authors: Denis L. Nika, Alexander A. BalandinAbstract:: A discovery of the unusual thermal properties of graphene stimulated experimental, theoretical and computational research directed at understanding phonon transport and thermal conduction in two-dimensional material systems. We provide a critical review of recent results in the graphene thermal field focusing on phonon dispersion, specific heat, thermal conductivity, and comparison of different models and computational approaches. The correlation between the phonon spectrum in graphene-based materials and the heat conduction properties is analyzed in details. The effects of the Atomic Plane rotations in bilayer graphene, isotope engineering, and relative contributions of different phonon dispersion branches are discussed. For readers’ convenience, the summaries of main experimental and theoretical results on thermal conductivity as well as phonon mode contributions to thermal transport are provided in the form of comprehensive annotated tables.
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engineering of the thermodynamic properties of bilayer graphene by Atomic Plane rotations the role of the out of Plane phonons
Nanoscale, 2015Co-Authors: Denis L. Nika, Alexandr I. Cocemasov, Alexander A. BalandinAbstract:We investigated theoretically the specific heat of graphene, bilayer graphene and twisted bilayer graphene taking into account the exact phonon dispersion and density of states for each polarization branch. It is shown that contrary to a conventional belief the dispersion of the out-of-Plane acoustic phonons – referred to as ZA phonons – deviates strongly from a parabolic law starting from the frequencies as low as ∼100 cm−1. This leads to the frequency-dependent ZA phonon density of states and the breakdown of the linear dependence of the specific heat on temperature T. We established that ZA phonons determine the specific heat for T ≤ 200 K while contributions from both in-Plane and out-of-Plane acoustic phonons are dominant for 200 K ≤ T ≤ 500 K. In the high-temperature limit, T > 1000 K, the optical and acoustic phonons contribute approximately equally to the specific heat. The Debye temperature for graphene and twisted bilayer graphene was calculated to be around ∼1861–1864 K. Our results suggest that the thermodynamic properties of materials such as bilayer graphene can be controlled at the Atomic scale by rotation of the sp2-carbon Planes.
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Specific heat of twisted bilayer graphene: Engineering phonons by Atomic Plane rotations
Applied Physics Letters, 2014Co-Authors: Denis L. Nika, Alexandr I. Cocemasov, Alexander A. BalandinAbstract:We have studied the phonon specific heat in single-layer, bilayer, and twisted bilayer graphene. The calculations were performed using the Born-von Karman model of lattice dynamics for intralayer Atomic interactions and spherically symmetric interAtomic potential for interlayer interactions. We found that at temperature T
Hideomi Koinuma – One of the best experts on this subject based on the ideXlab platform.
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in situ determination of the terminating layer of la0 7sr0 3mno3 thin films using coaxial impact collision ion scattering spectroscopy
Applied Physics Letters, 1998Co-Authors: Mamoru Yoshimoto, Hidenori Maruta, T Ohnishi, Kenji Sasaki, Hideomi KoinumaAbstract:In situ analysis of the terminating Atomic Plane of c-axis oriented La0.7Sr0.3MnO3 thin films grown epitaxially on SrTiO3(100) substrate by laser molecular beam epitaxy has been carried out employing coaxial impact-collision ion scattering spectroscopy (CAICISS). The CAICISS time-of-flight spectroscopic studies reveal that the (001) surface of c-axis oriented La0.7Sr0.3MnO3 thin films is predominantly terminated with MnO2 Plane. The azimuth rotational CAICISS measurements show a fourfold symmetry in the surface atom alignments establishing the square lattice structure of the terminating Plane.
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Atomic scale identification of the terminating structure of compound materials by CAICISS (coaxial impact collision ion scattering spectroscopy)
Applied Surface Science, 1997Co-Authors: Osamu Ishiyama, Mamoru Yoshimoto, Hideomi Koinuma, Makoto Shinohara, Takaharu Nishihara, Shigeki Hayashi, Tsuyoshi Ohnishi, Shigehiro Nishino, Junji SaraieAbstract:Abstract Quantitative surface analysis includes the determination of the elemental composition and the structure of the sample under investigation. Although LEED, XPS, and SPM etc. have been used to investigate the surface structure of the materials, ambiguity remains in determining quantitatively the topmost Atomic species and its alignment on an Atomic scale. Therefore, we adopted coaxial impact collision ion scattering spectroscopy (CAICISS) to identify the terminating structure of compound materials such as SrTiO3(001), InP(001) etc. As a result of the measurements, we could determine the topmost Atomic Plane of those materials. CAICISS is considered to be a powerful tool for those topmost surface analysis of the materials.
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In Situ Determination of Terminating Atomic Plane of SrTiO 3 (001) by Coaxial Impact Collision Ion Scattering Spectroscopy
Advances in Superconductivity VII, 1995Co-Authors: Osamu Ishiyama, Mamoru Yoshimoto, Fumihiko Ohtani, Tatsuro Maeda, Makoto Shinohara, Hideomi KoinumaAbstract:In situ characterization of the topmost surface of SrTiO3(001) was performed by means of coaxial impact collision ion scattering spectroscopy. As a result, it was proven that the displacement of Sr atoms occurred in the surface region at high temperatures around 500 °C in the case of the as-supplied SrTiO3 substrates terminated with TiO2 Atomic Plane. Sr atoms shifted by 0.012±0.002 nm toward [001] direction. On the other hand, no displacement was observed in the case of O2 annealed samples at 1000 °C for 10 hours. It indicated that the stable topmost surface structure was formed by the high temperature annealing in the SrTiO3 substrates.