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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
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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 < 15 K, specific heat varies with temperature as Tn, where n = 1 for graphene, n = 1.6 for bilayer graphene, and n = 1.3 for the twisted bilayer graphene. The phonon specific heat reveals an intriguing dependence on the twist angle in bilayer graphene, which is particularly pronounced at low temperature. The results suggest a possibility of phonon engineering of thermal properties of layered materials by twisting the Atomic Planes.
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Thermal Properties of Graphene–Copper–Graphene Heterogeneous Films
Nano Letters, 2014Co-Authors: Pradyumna Goli, Hao Ning, Xuesong Li, Ching Yu Lu, Kostya S. Novoselov, Alexander A. BalandinAbstract:We demonstrated experimentally that graphene–Cu–graphene heterogeneous films reveal strongly enhanced thermal conductivity as compared to the reference Cu and annealed Cu films. Chemical vapor deposition of a single Atomic Plane of graphene on both sides of 9 μm thick Cu films increases their thermal conductivity by up to 24% near room temperature. Interestingly, the observed improvement of thermal properties of graphene–Cu–graphene heterofilms results primarily from the changes in Cu morphology during graphene deposition rather than from graphene’s action as an additional heat conducting channel. Enhancement of thermal properties of graphene-capped Cu films is important for thermal management of advanced electronic chips and proposed applications of graphene in the hybrid graphene–Cu interconnect hierarchies.
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
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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 < 15 K, specific heat varies with temperature as Tn, where n = 1 for graphene, n = 1.6 for bilayer graphene, and n = 1.3 for the twisted bilayer graphene. The phonon specific heat reveals an intriguing dependence on the twist angle in bilayer graphene, which is particularly pronounced at low temperature. The results suggest a possibility of phonon engineering of thermal properties of layered materials by twisting the Atomic Planes.
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, Takaharu Nishihara, Shigehiro Nishino, Tsuyoshi Ohnishi, Makoto Shinohara, Shigeki Hayashi, Hideomi Koinuma, Mamoru Yoshimoto, 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, Tatsuro Maeda, Fumihiko Ohtani, Makoto Shinohara, Mamoru Yoshimoto, 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.
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The determination of Atomic Plane on InP (001) surface by CAICISS
Seventh International Conference on Indium Phosphide and Related Materials, 1995Co-Authors: T. Nishihara, M. Shinohara, O. Ishiyama, F. Ohtani, M. Yoshimoto, T. Maeda, Hideomi KoinumaAbstract:We have observed the sputtered and the annealed InP [001] surfaces to determine the species of the topmost Atomic Plane on these surfaces by coaxial impact collision ion scattering spectroscopy (CAICISS). We have identified that the indium top surface without serious roughness can be acquired by Ar/sup +/ sputtering even if the substrate temperature is as low as 300 /spl deg/C. In AFM observations, this surface exhibits textured structure, which is composed of double Atomic height steps. Furthermore, the azimuthal dependence of CAICISS spectra show two-fold symmetry with respect to the axis, which indicates that the crystalline quality of this surface is quite high. Therefore, we consider that this surface is applicable to the substrate for heteroepitaxial growth.
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topmost surface analysis of srtio3 001 by coaxial impact collision ion scattering spectroscopy
Applied Physics Letters, 1994Co-Authors: Mamoru Yoshimoto, Tatsuro Maeda, Kazuki Shimozono, Osamu Ishiyama, Makoto Shinohara, Hideomi Koinuma, Fumihiko OhtaniAbstract:The terminating Atomic Plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 Atomic Plane, while the SrO Atomic Plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost Atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating Plane.
Mamoru Yoshimoto - 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, Takaharu Nishihara, Shigehiro Nishino, Tsuyoshi Ohnishi, Makoto Shinohara, Shigeki Hayashi, Hideomi Koinuma, Mamoru Yoshimoto, 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, Tatsuro Maeda, Fumihiko Ohtani, Makoto Shinohara, Mamoru Yoshimoto, 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.
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topmost surface analysis of srtio3 001 by coaxial impact collision ion scattering spectroscopy
Applied Physics Letters, 1994Co-Authors: Mamoru Yoshimoto, Tatsuro Maeda, Kazuki Shimozono, Osamu Ishiyama, Makoto Shinohara, Hideomi Koinuma, Fumihiko OhtaniAbstract:The terminating Atomic Plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 Atomic Plane, while the SrO Atomic Plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost Atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating Plane.
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Topmost surface analysis of SrTiO3 (001) by coaxial impact‐collision ion scattering spectroscopy
Applied Physics Letters, 1994Co-Authors: Mamoru Yoshimoto, Tatsuro Maeda, Kazuki Shimozono, Osamu Ishiyama, Makoto Shinohara, Hideomi Koinuma, Fumihiko OhtaniAbstract:The terminating Atomic Plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 Atomic Plane, while the SrO Atomic Plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost Atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating Plane.
Fumihiko Ohtani - One of the best experts on this subject based on the ideXlab platform.
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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, Tatsuro Maeda, Fumihiko Ohtani, Makoto Shinohara, Mamoru Yoshimoto, 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.
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topmost surface analysis of srtio3 001 by coaxial impact collision ion scattering spectroscopy
Applied Physics Letters, 1994Co-Authors: Mamoru Yoshimoto, Tatsuro Maeda, Kazuki Shimozono, Osamu Ishiyama, Makoto Shinohara, Hideomi Koinuma, Fumihiko OhtaniAbstract:The terminating Atomic Plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 Atomic Plane, while the SrO Atomic Plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost Atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating Plane.
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Topmost surface analysis of SrTiO3 (001) by coaxial impact‐collision ion scattering spectroscopy
Applied Physics Letters, 1994Co-Authors: Mamoru Yoshimoto, Tatsuro Maeda, Kazuki Shimozono, Osamu Ishiyama, Makoto Shinohara, Hideomi Koinuma, Fumihiko OhtaniAbstract:The terminating Atomic Plane of SrTiO3 (001) surface was investigated by means of coaxial impact‐collision ion scattering spectroscopy (CAICISS). CAICISS spectra proved that SrTiO3 (001) surfaces of as‐supplied substrates as well as of O2‐annealed substrates were predominantly terminated with TiO2 Atomic Plane, while the SrO Atomic Plane came at the topmost surface of SrTiO3 (001) homoepitaxial film. This indicates the structural conversion of the topmost Atomic layer from TiO2 to SrO occurred during the SrTiO3 homoepitaxial growth. The azimuth rotational CAICISS spectra exhibited a fourfold symmetry in the surface atom alignments, showing the square lattice structure of a terminating Plane.