The Experts below are selected from a list of 56355 Experts worldwide ranked by ideXlab platform
Alexander Karlwalter Zettl - One of the best experts on this subject based on the ideXlab platform.
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Raman spectroscopy study of rotated double-Layer Graphene: Misorientation-angle dependence of electronic structure
Physical Review Letters, 2012Co-Authors: Kwanpyo Kim, Liang Z. Tan, Eric Chatterjee, Sinisa Coh, Jong Min Yuk, Michael F Crommie, William Regan, Marvin L. Cohen, Steven G. Louie, Alexander Karlwalter ZettlAbstract:We present a systematic Raman study of unconventionally stacked double-Layer Graphene, and find that the spectrum strongly depends on the relative rotation angle between Layers. Rotation-dependent trends in the position, width and intensity of Graphene 2D and G peaks are experimentally established and accounted for theoretically. Our theoretical analysis reveals that changes in electronic band structure due to the interLayer interaction, such as rotational-angle dependent Van Hove singularities, are responsible for the observed spectral features. Our combined experimental and theoretical study provides a deeper understanding of the electronic band structure of rotated double-Layer Graphene, and leads to a practical way to identify and analyze rotation angles of misoriented double-Layer Graphene.
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High-temperature stability of suspended single-Layer Graphene†
physica status solidi (RRL) - Rapid Research Letters, 2010Co-Authors: Kwanpyo Kim, Baisong Geng, Michael F Crommie, William Regan, Feng Wang, Benjamin Aleman, B. M. Kessler, Alexander Karlwalter ZettlAbstract:We report in situ Joule heating on suspended single-Layer Graphene in a transmission electron microscope (TEM). Thermally-driven degradation of pre-deposited nanoparticles on the membrane is monitored and used for local temperature estimation. By extrapolating the Joule heating power and temperature relation, we find that the suspended single-Layer Graphene has exceptional thermal stability up to at least 2600 K. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
G. Andrew D. Briggs - One of the best experts on this subject based on the ideXlab platform.
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Direct imaging of rotational stacking faults in few Layer Graphene.
Nano Letters, 2009Co-Authors: Jamie H. Warner, Mark H. Rümmeli, Thomas Gemming, Bernd Büchner, G. Andrew D. BriggsAbstract:Few Layer Graphene nanostructures are directly imaged using aberration corrected high-resolution transmission electron microscopy with an electron accelerating voltage of 80 kV. We observe rotational stacking faults in the HRTEM images of 2−6 Layers of Graphene sheets, giving rise to Moire patterns. By filtering in the frequency domain using a Fourier transform, we reconstruct the Graphene lattice of each sheet and determine the packing structure and relative orientations of up to six separate sets. Direct evidence is obtained for few Layer Graphene sheets with packing that is different to the standard AB Bernal packing of bulk graphite. This has implications toward biLayer and few Layer Graphene electronic devices and the determination of their intrinsic structure.
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Direct imaging of rotational stacking faults in few Layer Graphene.
Nano letters, 2009Co-Authors: Jamie H. Warner, Mark H. Rümmeli, Thomas Gemming, Bernd Büchner, G. Andrew D. BriggsAbstract:Few Layer Graphene nanostructures are directly imaged using aberration corrected high-resolution transmission electron microscopy with an electron accelerating voltage of 80 kV. We observe rotational stacking faults in the HRTEM images of 2-6 Layers of Graphene sheets, giving rise to Moir patterns. By filtering in the frequency domain using a Fourier transform, we reconstruct the Graphene lattice of each sheet and determine the packing structure and relative orientations of up to six separate sets. Direct evidence is obtained for few Layer Graphene sheets with packing that is different to the standard AB Bernal packing of bulk graphite. This has implications toward biLayer and few Layer Graphene electronic devices and the determination of their intrinsic structure.
Kwanpyo Kim - One of the best experts on this subject based on the ideXlab platform.
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Raman spectroscopy study of rotated double-Layer Graphene: Misorientation-angle dependence of electronic structure
Physical Review Letters, 2012Co-Authors: Kwanpyo Kim, Liang Z. Tan, Eric Chatterjee, Sinisa Coh, Jong Min Yuk, Michael F Crommie, William Regan, Marvin L. Cohen, Steven G. Louie, Alexander Karlwalter ZettlAbstract:We present a systematic Raman study of unconventionally stacked double-Layer Graphene, and find that the spectrum strongly depends on the relative rotation angle between Layers. Rotation-dependent trends in the position, width and intensity of Graphene 2D and G peaks are experimentally established and accounted for theoretically. Our theoretical analysis reveals that changes in electronic band structure due to the interLayer interaction, such as rotational-angle dependent Van Hove singularities, are responsible for the observed spectral features. Our combined experimental and theoretical study provides a deeper understanding of the electronic band structure of rotated double-Layer Graphene, and leads to a practical way to identify and analyze rotation angles of misoriented double-Layer Graphene.
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High-temperature stability of suspended single-Layer Graphene†
physica status solidi (RRL) - Rapid Research Letters, 2010Co-Authors: Kwanpyo Kim, Baisong Geng, Michael F Crommie, William Regan, Feng Wang, Benjamin Aleman, B. M. Kessler, Alexander Karlwalter ZettlAbstract:We report in situ Joule heating on suspended single-Layer Graphene in a transmission electron microscope (TEM). Thermally-driven degradation of pre-deposited nanoparticles on the membrane is monitored and used for local temperature estimation. By extrapolating the Joule heating power and temperature relation, we find that the suspended single-Layer Graphene has exceptional thermal stability up to at least 2600 K. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Carlos Drummond - One of the best experts on this subject based on the ideXlab platform.
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Surfactant-free single-Layer Graphene in water
Nature Chemistry, 2017Co-Authors: George Bepete, Eric Anglaret, Luca Ortolani, Vittorio Morandi, Kai Huang, Alain Pénicaud, Carlos DrummondAbstract:Dispersing graphite in water to obtain true (single-Layer) Graphene in bulk quantity in a liquid has been an unreachable goal for materials scientists in the past decade. Similarly, a diagnostic tool to identify solubilized Graphene in situ has been long awaited. Here we show that homogeneous stable dispersions of single-Layer Graphene (SLG) in water can be obtained by mixing graphenide (negatively charged Graphene) solutions in tetrahydrofuran with degassed water and evaporating the organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics of SLG. Transmission electron and atomic force microscopies on deposits confirm the single-Layer character. The resulting additive-free stable water dispersions contain 400 m^2 l^–1 of developed Graphene surface. Films prepared from these dispersions exhibit a conductivity of up to 32 kS m^–1. Aggregation usually prevents dissolution of Graphene in water. Now, hydroxide ion adsorption has been shown to allow the stabilization of true single-Layer Graphene in water — with no surfactant required — so long as the liquid is degassed beforehand. The resulting aqueous dispersions can contain high concentrations of exfoliated Graphene that are stable for several months.
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Surfactant-free single-Layer Graphene in water
Nature Chemistry, 2016Co-Authors: George Bepete, Eric Anglaret, Luca Ortolani, Vittorio Morandi, Kai Huang, Alain Pénicaud, Carlos DrummondAbstract:Dispersing graphite in water to obtain true (single-Layer) Graphene in bulk quantity in a liquid has been an unreachable goal for materials scientists in the past decade. Similarly, a diagnostic tool to identify solubilized Graphene in situ has been long awaited. Here we show that homogeneous stable dispersions of single-Layer Graphene (SLG) in water can be obtained by mixing graphenide (negatively charged Graphene) solutions in tetrahydrofuran with degassed water and evaporating the organic solvent. In situ Raman spectroscopy of these aqueous dispersions shows all the expected characteristics of SLG. Transmission electron and atomic force microscopies on deposits confirm the single-Layer character. The resulting additive-free stable water dispersions contain 400 m2 l–1 of developed Graphene surface. Films prepared from these dispersions exhibit a conductivity of up to 32 kS m–1.
Jamie H. Warner - One of the best experts on this subject based on the ideXlab platform.
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Direct imaging of rotational stacking faults in few Layer Graphene.
Nano Letters, 2009Co-Authors: Jamie H. Warner, Mark H. Rümmeli, Thomas Gemming, Bernd Büchner, G. Andrew D. BriggsAbstract:Few Layer Graphene nanostructures are directly imaged using aberration corrected high-resolution transmission electron microscopy with an electron accelerating voltage of 80 kV. We observe rotational stacking faults in the HRTEM images of 2−6 Layers of Graphene sheets, giving rise to Moire patterns. By filtering in the frequency domain using a Fourier transform, we reconstruct the Graphene lattice of each sheet and determine the packing structure and relative orientations of up to six separate sets. Direct evidence is obtained for few Layer Graphene sheets with packing that is different to the standard AB Bernal packing of bulk graphite. This has implications toward biLayer and few Layer Graphene electronic devices and the determination of their intrinsic structure.
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Direct imaging of rotational stacking faults in few Layer Graphene.
Nano letters, 2009Co-Authors: Jamie H. Warner, Mark H. Rümmeli, Thomas Gemming, Bernd Büchner, G. Andrew D. BriggsAbstract:Few Layer Graphene nanostructures are directly imaged using aberration corrected high-resolution transmission electron microscopy with an electron accelerating voltage of 80 kV. We observe rotational stacking faults in the HRTEM images of 2-6 Layers of Graphene sheets, giving rise to Moir patterns. By filtering in the frequency domain using a Fourier transform, we reconstruct the Graphene lattice of each sheet and determine the packing structure and relative orientations of up to six separate sets. Direct evidence is obtained for few Layer Graphene sheets with packing that is different to the standard AB Bernal packing of bulk graphite. This has implications toward biLayer and few Layer Graphene electronic devices and the determination of their intrinsic structure.
