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Experimental Methods for Graphene
Published in Hualin Zhan, Graphene-Electrolyte Interfaces, 2020
Angle-resolved photoemission spectroscopy (ARPES) is particularly useful for the study of low dimensional materials, because the photon is injected to a very thin layer on the surface of the material. Similar to most photoemission techniques, photons with sufficient energy strike the sample and knock out the electrons which carries the information of their energy in the material. In addition, the detector for ARPES can change its angle and find the direction that the emitted electrons move. This would determine the momentum of the electrons, and hence plot the energy-vs.-momentum relation, i.e., the electronic band structure.
Essential Properties of Fluorinated Graphene and Graphene Nanoribbons
Published in Olga E. Glukhova, 2D and 3D Graphene Nanocomposites, 2019
Duy Khanh Nguyen, Ngoc Thanh Thuy Tran, Thanh Tien Nguyen, Yu-Huang Chiu, Ming-Fa Lin
Angle-resolved photoemission spectroscopy (ARPES), a direct experimental technique to observe the distribution of electrons in the reciprocal space of solids, is one of the most powerful experimental methods to examine the wave-vector-dependent electronic structures. Besides, the feature-rich electronic structures within the distinct dimensions are revealed in the experimental measurements on graphene-related systems. For example, the verified energy bands include an isotropic Dirac-cone structure with linear energy dispersions in monolayer graphene [53], two pairs of parabolic bands in bilayer AB stacking [54], the bilayer- and monolayer-like energy dispersions, respectively, at kz = 0 and zone boundary in AB-stacked graphite [55] and 1D parabolic energy bands with a direct energy gap in AGNRs [56]. In addition, an edge-localized partially flat band is deduced to have an association with the zigzag-like steps on graphite surface. The measurement on fluorinated graphene shows that the Fermi level is shifted 0.79 eV below the Dirac point, indicating the p-type doping. Up to now, the ARPES measurements on the adatom-enriched 1D energy bands of GNRs are absent. The ARPES and spin-resolved ARPES [57] are available in verifying five kinds of predicted electronic and magnetic configurations in F-adatom-absorbed GNRs.
Rich Essential Properties of Si-Doped Graphene
Published in Ming-Fa Lin, Wen-Dung Hsu, Green Energy Materials Handbook, 2019
Duy Khanh Nguyen, Shih-Yang Lin, Ngoc Thanh Thuy Tran, Hsin-Yi Liu, Ming-Fa Lin
Angle-resolved photoemission spectroscopy (ARPES) is the only tool in measuring the wave-vector-dependent occupied electronic states, especially for valence and conduction bands crossing the Fermi level. The details of experimental equipment could be found in the books written by Tran et al.93 and Lin et al.94 Up to now, the high-resolution ARPES measurements have identified the rich band structures in graphene-related systems, being greatly diversified by the distinct geometric symmetries, dimensions, stacking configurations, numbers of layers, and absorptions, substitutions, and intercalations. For example, the verified electronic structures, which are consistent under the theoretical predictions95 and the experimental measurements,96 include parabolic valence bands with an energy gap in the 1D graphene nanoribbons97; the linear Dirac-cone structure in monolayer graphene98; the blue shift of the Fermi level in alkali-adsorbed graphene systems99; two parabolic valence bands near EF = 0 without energy gap in bilayer AB-stacked graphene100; the monolayer- and bilayer-like valence bands in trilayer ABA stacking; the partially flat, sombrero-shaped, and linear bands in trilayer ABC stacking101; and the parabolic and linear energy dispersions near the K and H points (k z= 0 and π) in a natural graphite.102 The similar ARPES measurements are available in thoroughly examining the significant effects on band structures after the chemisorptions and substitutions of Si–guest atoms. They are conducted on the finite or vanishing band gap; the numbers of the valence and conduction bands intersecting the Fermi level near the Г, K, and M points; and the existence/destruction of the carbon-dominated σ bands at the Г point initiated from –4.1 eV to –4.2 eV. Such detailed information is sufficient in determining the critical multi-orbital hybridizations of C–Si bonds or the p–sp3 or sp2–sp2 bondings.
Catalytic applications of phosphorene: Computational design and experimental performance assessment
Published in Critical Reviews in Environmental Science and Technology, 2023
Monika Nehra, Neeraj Dilbaghi, Rajesh Kumar, Sunita Srivastava, K. Tankeshwar, Ki-Hyun Kim, Sandeep Kumar
The Young’ s modulus of few layer phosphorene was measured to be 27.2 ± 4.1 and 58.6 ± 11.7 GPa in armchair and zigzag directions, respectively (Tao et al., 2015). The bulk black phosphorous is a direct band gap semiconductor (0.3 eV) as examined by angle-resolved photoemission spectroscopy and first-principles calculations. In the case of monolayer phosphorene, the band gap gradually increases with a decrease in thickness due to quantum confinement, reaching a band gap of 2 eV. Unlike the band gap transition (indirect-to-direct) in the transition-metal dichalcogenide (TMDC) family, all samples of few-layer phosphorene are direct band gap semiconductors with the same band topology and changing thickness. The characteristics of phosphorene (i.e. elastic and plastic) have also been investigated for atomic adsorption based on DFT (Aghdasi et al., 2021). Under different loadings (e.g. uniaxial and bi-axial) to both forms of phosphorene (such as pristine and adsorbed), the impact of the atomic adsorption on in-plane Young’s modulus was more significant in armchair phosphorene than the zigzag configuration. The small strains are quite enough for the zigzag phosphorene to reach the plastic region. Moreover, the adsorption of different atoms (like iodine, bromine, chlorine, and fluorine) on the surface of phosphorene has a significant impact over its structural and electronic properties. For instance, it can cause transition of phosphorene from a direct to indirect band gap semiconductor, along with inducing a spin-polarized defect state, as investigated using DFT (Taylor et al., 2020).
Enhancement of superconductivity by electronic nematicity in cuprate superconductors
Published in Philosophical Magazine, 2022
Zhangkai Cao, Yiqun Liu, Huaiming Guo, Shiping Feng
Angle-resolved photoemission spectroscopy (ARPES) experiments [56–59] measure the single-particle excitation spectrum, while the underlying EFS contour in momentum space is directly obtained by the trace of the peak positions in the single-particle excitation spectrum. In the absence of any sort of symmetry-breaking, the shape of EFS of cuprate superconductors reflects the underlying symmetry of the square-lattice CuO plane. In particular, the shape of EFS has deep consequences for the low-energy properties [5–11] and has been also central to addressing multiple electronic orders [9–25]. This is why the determination of the shape of EFS in cuprate superconductors is believed to be key issue for the understanding of the physical origin of different electronic ordered (then density-wave) states and of their intimate interplay with superconductivity.
Chemical modification of group IV graphene analogs
Published in Science and Technology of Advanced Materials, 2018
Hideyuki Nakano, Hiroyuki Tetsuka, Michelle J. S. Spencer, Tetsuya Morishita
The electronic properties of silicene in a CaSi2 single crystal have been analyzed by high-resolution angle-resolved photoemission spectroscopy (ARPES) [78]. In the ARPES-derived band structure, a massless Dirac cone of dispersed π-electrons at the K(H) point in the Brillouin zone was clearly observed, together with σ-band dispersions at the Γ point. Furthermore, the Dirac point was located at approximately 2 eV from the Fermi level, thereby revealing a substantial charge transfer from the Ca atoms to the silicene layers. The ARPES results indicated that the sp2 bonding framework essentially maintains the CaSi2 structure, thereby producing a massless Dirac-cone state at the K point, despite the strongly buckled structure of the silicene layers (i.e. the graphene-like electronic structure is stably formed in this metal-intercalated multilayer silicene).