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Full-Text Articles in Engineering
Room-Temperature Strong Terahertz Photon Mixing In Graphene, Sultan Shareef, Yee Sin Ang, Chao Zhang
Room-Temperature Strong Terahertz Photon Mixing In Graphene, Sultan Shareef, Yee Sin Ang, Chao Zhang
Faculty of Engineering - Papers (Archive)
We demonstrate that single layer graphene exhibits a strong nonlinear photon-mixing effect in the terahertz frequency regime. Up to room temperature, the third-order nonlinear current in graphene grows rapidly with increasing temperature. The third-order nonlinear current can be as strong as the linear current under a moderate electric field strength of 104 V∕cm. Because of the unique Dirac behavior of the graphene quasi-particles, low Fermi level and electron fillings optimizes the optical nonlinearity. Under a strong-field condition, the strong-field-induced Dirac fermion population redistribution and nonequilibrium carrier heating effects further amplify the optical nonlinearity of graphene. Our results suggest that doped …
How To Achieve Maximum Charge Carrier Loading On Heteroatom-Substituted Graphene Nanoribbon Edges: Density Functional Theory Study, Ting Liao, Chenghua Sun, Ziqi Sun, Aijun Du, Denisa Hulicova-Jurcakova, Sean C. Smith
How To Achieve Maximum Charge Carrier Loading On Heteroatom-Substituted Graphene Nanoribbon Edges: Density Functional Theory Study, Ting Liao, Chenghua Sun, Ziqi Sun, Aijun Du, Denisa Hulicova-Jurcakova, Sean C. Smith
Faculty of Engineering - Papers (Archive)
The practical number of charge carriers loaded is crucial to the evaluation of the capacity performance of carbon-based electrodes in service, and cannot be easily addressed experimentally. In this paper, we report a density functional theory study of charge carrier adsorption onto zigzag edge-shaped graphene nanoribbons (ZGNRs), both pristine and incorporating edge substitution with boron, nitrogen or oxygen atoms. All edge substitutions are found to be energetically favorable, especially in oxidized environments. The maximal loading of protons onto the substituted ZGNR edges obeys a rule of [8-n- 1], where n is the number of valence electrons of the edge-site atom …
The Effect Of Reduced Graphene Oxide Addition On The Superconductivity Of Mgb2, K S. B De Silva, S Gambhir, Xiaolin Wang, X Xu, W X. Li, David L. Officer, D Wexler, G G. Wallace, S. X. Dou
The Effect Of Reduced Graphene Oxide Addition On The Superconductivity Of Mgb2, K S. B De Silva, S Gambhir, Xiaolin Wang, X Xu, W X. Li, David L. Officer, D Wexler, G G. Wallace, S. X. Dou
Faculty of Engineering - Papers (Archive)
Reduced graphene oxide (rGO) and highly reduced chemically converted graphene (ICCO) samples were prepared under different processing condition! and were doped into MgBz by a diffusion process at 800 °C for 10 houn. It was demonstrated that a small addition rCCG can significantly improve the supcn;onducting properties of MgBz. Doping of M8B2 with 1 mol% of rCCG resulted in a Ie of 5.45 X lOS A cm-2 at 20 K in self-fields, which il nearly 32% improvement over that of the undopcd sample. This is a significant improvement as most carbon sources adversely affect the Ie performance: at the zero …
Terahertz Photon Mixing Effect In Gapped Graphene, Yee Sin Ang, Shareef Sultan, Asya Tawfiq, Juncheng Cao, Chao Zhang
Terahertz Photon Mixing Effect In Gapped Graphene, Yee Sin Ang, Shareef Sultan, Asya Tawfiq, Juncheng Cao, Chao Zhang
Faculty of Engineering - Papers (Archive)
We theoretically calculate the terahertz waves mixing effect in doped graphene with a finite bandgap. The temperature dependence of the nonlinear intraband optical response at bandgap opening of few tens of meVare investigated. When the external electric field is weak, a moderate level of bandgap opening is found to slightly enhance the nonlinear optical response. The optical response is however significantly altered under strong-field condition. The strong-field nonlinear optical conductivity exhibits two distinct response ‘hot spot’: (i) low temperature with large bandgap and (ii) high temperature with small bandgap. The electric field required for the nonlinear response to dominate over …
Carbon Nanotube/Graphene Nanocomposite As Efficient Counter Electrodes In Dye-Sensitized Solar Cells, Josef Velten, Attila J. Mozer, Dan Li, David Officer, G G. Wallace, Ray Baughman, A Zakhidov
Carbon Nanotube/Graphene Nanocomposite As Efficient Counter Electrodes In Dye-Sensitized Solar Cells, Josef Velten, Attila J. Mozer, Dan Li, David Officer, G G. Wallace, Ray Baughman, A Zakhidov
Faculty of Engineering - Papers (Archive)
We demonstrated the replacement of the Pt catalyst normally used in the counter electrode of a dye-sensitized solar cell (DSSC) by a nanocomposite of dry spun carbon multi-walled nanotube (MWNT) sheets with graphene flakes (Gr-F). The effectiveness of this counter electrode on the reduction of the triiodide in the iodide/triiodide redox (I−/I− 3 ) redox reaction was studied in parallel with the use of the dry spun carbon MWNT sheets alone and graphene flakes used independent of each other. This nanocomposite deposited onto fluorinated tin-oxide-coated glass showed improved catalytic behavior and power conversion efficiency (7.55%) beyond the use of the …
A Significant Improvement In The Superconducting Properties Of Mgb2 By Co-Doping With Graphene And Nano-Sic, K S B De Silva, X Xu, Xiaolin Wang, D Wexler, D Attard, F Xiang, S. X. Dou
A Significant Improvement In The Superconducting Properties Of Mgb2 By Co-Doping With Graphene And Nano-Sic, K S B De Silva, X Xu, Xiaolin Wang, D Wexler, D Attard, F Xiang, S. X. Dou
Faculty of Engineering - Papers (Archive)
The effects of graphene (G) and nanosilicon carbide (SiC) co-doping on the superconducting properties of MgB2 were studied using bulk samples. SiC remains one of the best dopants which can significantly improve the high field performance, while graphene is emerging as a new dopant for MgB2, which can improve the zero field critical current density (Jc). The superconducting properties characterized by Jc, the intergrain connectivity, and the critical fields were significantly improved by the use of both SiC and graphene as dopants.
Globular Reduced Graphene Oxide-Metal Oxide Structures For Energy Storage Applications, Alfred Chidembo, Seyed Hamed Aboutalebi, Konstantin Konstantinov, Maryam Salari, Brad R. Winton, Sima Aminorroaya-Yamini, Ivan Nevirkovets, Hua-Kun Liu
Globular Reduced Graphene Oxide-Metal Oxide Structures For Energy Storage Applications, Alfred Chidembo, Seyed Hamed Aboutalebi, Konstantin Konstantinov, Maryam Salari, Brad R. Winton, Sima Aminorroaya-Yamini, Ivan Nevirkovets, Hua-Kun Liu
Faculty of Engineering - Papers (Archive)
In this work, we employed an in situ spray pyrolysis approach to fabricate metal oxide-graphene composites with highly porous morphologies.The materials exhibited unique globular structures comprising metal oxide nanoparticles embedded between graphene sheets with high capacitance.
Facile Synthesis Of Graphene-Molybdenum Dioxide And Its Lithium Storage Properties, Kuok Hau Seng, Guo Dong Du, Li Li, Zhixin Chen, Hua-Kun Liu, Zaiping Guo
Facile Synthesis Of Graphene-Molybdenum Dioxide And Its Lithium Storage Properties, Kuok Hau Seng, Guo Dong Du, Li Li, Zhixin Chen, Hua-Kun Liu, Zaiping Guo
Faculty of Engineering - Papers (Archive)
Graphene–molybdenum dioxide composites in several ratios have been prepared through a facile synthesis method. Depending on the ratio, the as synthesized composites have either 2-dimensional graphene sheets with MoO2 particles anchored to them or a clustered agglomerate morphology. The composites have been characterised using Raman spectroscopy, X-ray diffraction, and electron diffraction to confirm the monoclinic MoO2 phase that is present. Lithium storage properties of the as-synthesised samples were tested in a coin-type half cell assembly to determine the relationship between the ratio and the electrochemical performance. The sample with highest amount of MoO2 (78 wt%) displayed the most promising lithium …
Retro Reflection Of Electrons At The Interface Of Bilayer Graphene And Superconductor, Yee Sin Ang, Zhongshui Ma, C Zhang
Retro Reflection Of Electrons At The Interface Of Bilayer Graphene And Superconductor, Yee Sin Ang, Zhongshui Ma, C Zhang
Faculty of Engineering - Papers (Archive)
Electron reflection at an interface is a fundamental quantum transport phenomenon. The most famous electron reflection is the electronRhole Andreev reflection (AR) at a metal/superconductor interface. While AR can be either specular or retro-type, electronRelectron reflection is limited to only the specular type. Here we show that electrons can undergo retro-reflection in bilayer graphene (BLG). The underlying mechanism for this previously unknown process is the anisotropic constant energy band contour of BLG. The electron group velocity is fully reversed upon reflection, causing electrons to be retro-reflected. Utilizing a BLG/superconductor junction (BLG/S) as a model structure, we show that the unique …
Graphene Wrapped Lifepo4/C Composites As Cathode Materials For Li-Ion Batteries With Enhanced Rate Capability, Yi Shi, Shulei Chou, Jia-Zhao Wang, David Wexler, Hui-Jun Li, Hua-Kun Liu, Yuping Wu
Graphene Wrapped Lifepo4/C Composites As Cathode Materials For Li-Ion Batteries With Enhanced Rate Capability, Yi Shi, Shulei Chou, Jia-Zhao Wang, David Wexler, Hui-Jun Li, Hua-Kun Liu, Yuping Wu
Faculty of Engineering - Papers (Archive)
To reduce the reaction time, electrical energy consumption, and cost, LiFePO4/C/graphene has been synthesized by a rapid, one-pot, microwave-assisted hydrothermal method within 15 min at a temperature of 200 °C, followed by sintering at 600 °C for 2 h under a H2/Ar (5:95, v/v) atmosphere. The microstructure and morphology of the LiFePO4/C/graphene products were characterized by means of X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy, and transmission electron microscopy. The carbon coated LiFePO4/C nanoparticles, around 200 nm in size, are thoroughly wrapped by crumpled micrometer-size graphene sheets. In this kind …
Dependence Of Magnetoelectric Properties On Sintering Temperature For Nano-Sic-Doped Mgb2/Fe Wires Made By Combined In Situ/Ex Situ Process, Wenxian Li, Rong Zeng, Jiazhao Wang, Y Li, S. X. Dou
Dependence Of Magnetoelectric Properties On Sintering Temperature For Nano-Sic-Doped Mgb2/Fe Wires Made By Combined In Situ/Ex Situ Process, Wenxian Li, Rong Zeng, Jiazhao Wang, Y Li, S. X. Dou
Faculty of Engineering - Papers (Archive)
Very fine nano-SiC particles (nm) were doped into a MgB2 superconductor. The influence of self-field supercurrent on the high-field performance of the nano-SiC-doped MgB2/Fe wires is discussed based on comparison of the critical current densities of the in situ processed nano-SiCdoped MgB2 wires and those of the nano-SiC-doped MgB2/Fe wires processed by the combination of in situ/ex situ methods.
Charge Carrier Exchange At Chemically Modified Graphene Edges: A Density Functional Theory Study, Ting Liao, Chenghua Sun, Aijun Du, Ziqi Sun, Denisa Hulicova-Jurcakova, Sean Smith
Charge Carrier Exchange At Chemically Modified Graphene Edges: A Density Functional Theory Study, Ting Liao, Chenghua Sun, Aijun Du, Ziqi Sun, Denisa Hulicova-Jurcakova, Sean Smith
Faculty of Engineering - Papers (Archive)
Heteroatom doping on the edge of graphene may serve as an effective way to tune chemical activity of carbon-based electrodes with respect to charge carrier transfer in an aqueous environment. In a step towards developing mechanistic understanding of this phenomenon, we explore herein mechanisms of proton transfer from aqueous solution to pristine and doped graphene edges utilizing density functional theory. Atomic B-, N-, and O- doped edges as well as the native graphene are examined, displaying varying proton affinities and effective interaction ranges with the H3O+ charge carrier. Our study shows that the doped edges characterized by more dispersive orbitals, …
Rapid Microwave-Assisted Synthesis Of Mn3o4-Graphene Nanocomposite And Its Lithium Storage Properties, Li Li, Zaiping Guo, Aijun Du, Hua-Kun Liu
Rapid Microwave-Assisted Synthesis Of Mn3o4-Graphene Nanocomposite And Its Lithium Storage Properties, Li Li, Zaiping Guo, Aijun Du, Hua-Kun Liu
Faculty of Engineering - Papers (Archive)
A nanocomposite of Mn3O4 wrapped in graphene sheets (GSs) was successfully synthesized via a facile, effective, energy-saving, and scalable microwave hydrothermal technique. The morphology and microstructures of the fabricated GS–Mn3O4 nanocomposite were characterized using various techniques. The results indicate that the particle size of the Mn3O4 particles in the nanocomposite markedly decreased to nearly 20 nm, significantly smaller than that for the bare Mn3O4. Electrochemical measurements demonstrated a high specific capacity of more than 900 mA h g−1 at 40 mA g−1, and excellent cycling stability with no capacity decay can be observed up to 50 cycles. All of these …
Graphene V2o5 Nh2o Xerogel Composite Cathodes For Lithium Ion Batteries, Guodong Du, Kuok Hau Seng, Zaiping Guo, Jun Liu, Wenxian Li, D Z. Jia, Christopher D. Cook, Z Liu, Hua-Kun Liu
Graphene V2o5 Nh2o Xerogel Composite Cathodes For Lithium Ion Batteries, Guodong Du, Kuok Hau Seng, Zaiping Guo, Jun Liu, Wenxian Li, D Z. Jia, Christopher D. Cook, Z Liu, Hua-Kun Liu
Faculty of Engineering - Papers (Archive)
A layer structured V2O5·nH2O xerogel was synthesized via a simple green hydrothermal technique by dissolving commercial V2O5 powder in de-ionized water and hydrogen peroxide. Graphene–V2O5·nH2O xerogel composites were then prepared by mixing and filtration of as-prepared V2O5·nH2O xerogel and graphene in the desired ratio. The method is a cost effective and energy saving way to prepare nanostructured composites. Structure and morphology were investigated by X-ray diffraction, thermogravimetric analysis, field emission scanning electron microscopy, …
Nonlinear Transverse Current Response In Zigzag Graphene Nanoribbons, Bo Wang, Zhongshui Ma, Chao Zhang
Nonlinear Transverse Current Response In Zigzag Graphene Nanoribbons, Bo Wang, Zhongshui Ma, Chao Zhang
Faculty of Engineering - Papers (Archive)
By employing a self-consistent approach, we reveal a number of unique properties of zigzag graphene nanoribbons under crossed electric and magnetic fields: (1) a very strong electrical polarization along the transverse direction of the ribbon, and (2) a strong nonlinear Hall current under a rather moderate electrical field. At the field strength of 5000 V/cm, the ratio of the nonlinear current to the linear current is around 1 under an applied magnetic field of 7.9 T. Our results suggest that graphene nanoribbons are an ideal system to achieve a large electrical polarizability. Our results also suggest that the nonlinear effect …
Transverse Current Response In Armchair Graphene Ribbons, Junfeng Liu, Zhongshui Ma, Chao Zhang
Transverse Current Response In Armchair Graphene Ribbons, Junfeng Liu, Zhongshui Ma, Chao Zhang
Faculty of Engineering - Papers (Archive)
We demonstrate that the direction of transverse current in graphene nanoribbons under a magnetic field can be tuned with a gate voltage. It is shown that for armchair ribbons there exist extra energy regions where the direction of the Hall current can be switched between positive and negative values. The directional change of the Hall current coincides with the special points where the two lowest energy bands in the spectrum become degenerate (band crossing points). The number of such degenerate points depends on the width of the ribbons. The dependence of the sign reversal on the gate voltage provides a …
Superconducting Properties Of Graphene Doped Magnesium Diboride, Xun Xu, Wenxian Li, Xiaolin Wang, S. X. Dou
Superconducting Properties Of Graphene Doped Magnesium Diboride, Xun Xu, Wenxian Li, Xiaolin Wang, S. X. Dou
Faculty of Engineering - Papers (Archive)
Graphene, carbon in the form of monolayer sheets, has revealed astonishing and unique chemical and physical properties, which have made it an extremely active research topic in both materials science and physics (Novoselov, K. S. et al., 2004). Through chemical and materials integration, graphene is being actively exploited in a range of technological applications (Stankovich, S. et al., 2006). Superconductors can carry electrical current without any energy dissipation. The combination of both graphene and a superconductor into a composite has great potential for electrical devices and large scale applications. MgB2, a superconductor with a simple composition and two-gap feature has …
Two-Color Terahertz Response In Bilayer Graphene Nanoribbons With Spin-Orbit Coupling, Junfeng Liu, Bo Wang, Zhongshui Ma, Chao Zhang
Two-Color Terahertz Response In Bilayer Graphene Nanoribbons With Spin-Orbit Coupling, Junfeng Liu, Bo Wang, Zhongshui Ma, Chao Zhang
Faculty of Engineering - Papers (Archive)
We demonstrate that spin-orbit coupling can give rise to a strong terahertz response in metallic armchair bilayer graphene nanoribbons. The combination of the interlayer coupling and the spin-orbit coupling leads to double resonant optical response in the low frequency regime. The frequency separation of the two excitations is tunable with a gate voltage.
Energy-Loss Rate Of A Fast Particle In Graphene, Yee Sin Ang, Chao Zhang, Chun Kee
Energy-Loss Rate Of A Fast Particle In Graphene, Yee Sin Ang, Chao Zhang, Chun Kee
Faculty of Engineering - Papers (Archive)
The energy-loss rate of a fast particle in graphene is studied. The energy-loss rate always increases with increasing incident particle energy, which is quite unusual when compared to electron gas in normal metal. Graphene exhibits a “discriminating” behavior where there exists a low energy cut-off below which the scattering process is strictly forbidden, leading to lossless traverse of an external particle in graphene. This low energy cutoff is of the order of nearest neighbor hopping bandwidth. Our results suggest that backscattering is also absent in the external particle scattering of graphene.
Gapless Insulator And A Band Gap Scaling Law In Semihydrogenated Graphene, Anthony Wright, T E. O'Brien, Chao Zhang, Dieter Beaven
Gapless Insulator And A Band Gap Scaling Law In Semihydrogenated Graphene, Anthony Wright, T E. O'Brien, Chao Zhang, Dieter Beaven
Faculty of Engineering - Papers (Archive)
We demonstrate two unusual electronic properties of semihydrogenated graphene with variable sized A- or B-hydrogenated domains within the tight-binding formalism as follows: (i) a universal band gap scaling law which states that the band gap depends linearly upon the ratio of the number of A- to B-hydrogenated atoms, NA/NB, reaching zero gap at NA = NB, but independent of the domain size, and (ii) an insulating state with zero band gap at NA = NB, a rare phenomenon in nature. We confirm this gapless insulator state by the zero …
Graphene Doping To Enhance The Flux Pinning And Supercurrent Carrying Ability Of A Magnesium Diboride Superconductor, Xun Xu, S X. Dou, Xiaolin Wang, Jung Ho Kim, John A. Stride, Mohammad Choucair, Weikong Yeoh, R K. Zheng, S P. Ringer
Graphene Doping To Enhance The Flux Pinning And Supercurrent Carrying Ability Of A Magnesium Diboride Superconductor, Xun Xu, S X. Dou, Xiaolin Wang, Jung Ho Kim, John A. Stride, Mohammad Choucair, Weikong Yeoh, R K. Zheng, S P. Ringer
Faculty of Engineering - Papers (Archive)
The effect of graphene doping on the electromagnetic properties of MgB2 has been examined, in comparison with the case for undoped MgB2. It was found that graphene doping is more efficient than other forms of carbon doping for effecting improvement in the critical current density–field performance (Jc(B)), with little change in the transition temperature of MgB2. An optimal enhancement of Jc(B) was achieved for 3.7 at.% graphene doped MgB2, by a factor of 30 at 5 K and 10 T, as compared to undoped MgB2. It is found that spatial fluctuation in Tc is responsible for the flux pinning mechanism …
The Resonant Tunneling Through A Graphene Multiquantum Well System, G.J Xu, X.G Xu, B.H Wu, J.C Cao, Chao Zhang
The Resonant Tunneling Through A Graphene Multiquantum Well System, G.J Xu, X.G Xu, B.H Wu, J.C Cao, Chao Zhang
Faculty of Engineering - Papers (Archive)
The transport properties of a graphene multiquantum well system are investigated numerically using transfer-matrix method. There are transmission gaps for electrons and holes in the transmission spectra at tilted incidence. In the transmission gaps, a few resonant tunneling peaks appear, defined as transmission windows, which are related with the bound states in the quantum wells. Unlike conventional semiconductor nanostructures, the location and the width of the transmission windows are sensitive not only to the quantum well width but also the incident angle. The number of the quantum wells determines the fine structure of the transmission windows. The anisotropic property is …
Vertical Absorption Edge And Temperature Dependent Resistivity In Semihydrogenated Graphene, Lei Chen, Zhongshui Ma, Chao Zhang
Vertical Absorption Edge And Temperature Dependent Resistivity In Semihydrogenated Graphene, Lei Chen, Zhongshui Ma, Chao Zhang
Faculty of Engineering - Papers (Archive)
We show that for graphene with any finite asymmetry in the on-site energy between the two sublattices (Δ), the optical absorption edge is determined by the Δ. The universal conductance will be broken and the conductance near the band edge varies with frequency as 1/ω2. The onset conductance is σc = 2σ0 = πe2/2h, independent of the size of the band gap. The total integrated optical response is nearly conserved despite of the opening of the band gap. Moreover, near the band edge, there is a change over of …
Dynamic Conductivity Of Graphene With Electron-Lo-Phonon Interaction, Anthony Wright, Chao Zhang
Dynamic Conductivity Of Graphene With Electron-Lo-Phonon Interaction, Anthony Wright, Chao Zhang
Faculty of Engineering - Papers (Archive)
We calculate the electrical conductivity of single-layer graphene within the regime of massless Dirac fermions. We consider the electron-LO-phonon interactions as the dominant scattering mechanism. By using the Green’s-function method, we are able to obtain the quantitative contribution from the five leading diagrams in the high-frequency approximation. It is found that electron-LO-phonon interactions cause an increase to the electromagnetic absorption of single-layer graphene of as much as 20% at room temperature. The spectrum is dominated by a continuum contribution with a peak at ω=ωLO/2 and represents intraband transitions. The temperature and doping dependence of these peak corrections is …
Nonlinear Optical Conductance In A Graphene Pn Junction In The Terahertz Regime, X.G Xu, S Sultan, Chao Zhang, J.C Cao
Nonlinear Optical Conductance In A Graphene Pn Junction In The Terahertz Regime, X.G Xu, S Sultan, Chao Zhang, J.C Cao
Faculty of Engineering - Papers (Archive)
We show that the optical responses of a graphene pn junction is dominated by nonlinear intraband and interband processes. At the experimentally relevant electric field intensity, nonlinear conductance is an order of magnitude larger than the linear conductance. Furthermore, the total conductance is negative in the terahertz to far infrared regime. The negative conductance provides a unique mechanism for photon generation in graphene and could be used for developing coherent terahertz radiation sources.
Strong Nonlinear Optical Response In Graphene In Terahertz Regime, Anthony Wright, Xuguang Xu, J. C. Cao, Chao Zhang
Strong Nonlinear Optical Response In Graphene In Terahertz Regime, Anthony Wright, Xuguang Xu, J. C. Cao, Chao Zhang
Faculty of Engineering - Papers (Archive)
We demonstrate that within the model of massless Dirac fermions, graphene has a strong nonlinear optical response in the terahertz regime. It is found that the nonlinear contribution significantly alters both the single frequency and frequency tripled optical response at experimentally relevant field strengths. The optical activity of single layer graphene is significantly enhanced by nonlinear effects, and the frequency tripled response opens the gateway to photonic and optoelectronic device applications.
First-Principles Study On The Enhancement Of Lithium Storage Capacity In Boron Doped Graphene, Xianlong Wang, Zhi Zeng, Hyojun Ahn, Guoxiu Wang
First-Principles Study On The Enhancement Of Lithium Storage Capacity In Boron Doped Graphene, Xianlong Wang, Zhi Zeng, Hyojun Ahn, Guoxiu Wang
Faculty of Engineering - Papers (Archive)
The adsorption of Li ions on boron doped graphene was investigated using a first-principles method. Our results show that, as boron doping turns graphene into an electron-deficient system, more Li ions can be captured around boron doped centers than in pristine graphene. One boron atom doped into graphene (6C ring unit) can adsorb six Li ions, which indicates that boron doped graphene is an efficient Li-ion storage material for lithium batteries. Further investigations show that, under limited conditions, boron doped graphene (BC5) can form Li6BC5 compound after Li-ion adsorption, corresponding to a lithium storage capacity …
Stretching Induced Hall Current And Conductance Anisotropy In Graphene, A R Wright, Chao Zhang
Stretching Induced Hall Current And Conductance Anisotropy In Graphene, A R Wright, Chao Zhang
Faculty of Engineering - Papers (Archive)
We evaluate the effect of stretching on the optical conductance of a single layer graphene sheet. It is found that the low energy (Dirac regime) isotropy that leads to the `universal conductance' is lost. More significantly, due to the loss of C_3 symmetry, a non-zero Hall conductance emerges for stretching along chiral directions, reaching a maximum at a stretching angle of 45 degrees, and being as high a S_0 = e2/4h at van Hove singular point for bond angle changes of about 2 degrees.
Enhanced Optical Conductivity Of Bilayer Graphene Nanoribbons In The Terahertz Regime, Anthony Wright, Chao Zhang, Juncheng Cao
Enhanced Optical Conductivity Of Bilayer Graphene Nanoribbons In The Terahertz Regime, Anthony Wright, Chao Zhang, Juncheng Cao
Faculty of Engineering - Papers (Archive)
We reveal that there exists a class of graphene structures (a sub-class of bilayer graphene nanoribbons) which has an exceptionally strong optical response in the terahertz (THz) and far infrared (FIR) regime. The peak conductance of THz/FIR active bilayer ribbons is around two orders of magnitude higher than the universal conductance of $\sigma_0=e^2/4\hbar$ observed in graphene sheets. The criterion for the THz/FIR active sub-class is a bilayer graphene nanoribbon with a one-dimensional massless Dirac Fermion energy dispersion near the $\Gamma$ point. Our results overcome a significant obstacle that hinders potential application of graphene in electronics and photonics.
Orbital Magnetization Of Graphene And Graphene Nanoribbons, Junfeng Liu, Zhongshui Ma, Anthony Wright, Chao Zhang
Orbital Magnetization Of Graphene And Graphene Nanoribbons, Junfeng Liu, Zhongshui Ma, Anthony Wright, Chao Zhang
Faculty of Engineering - Papers (Archive)
We present a quantitative analysis on orbital magnetization of graphene under a magnetic field. Theenergy spectra were obtained by solving Harper equation for a honeycomb lattice. The effect of thenext-nearest-neighbor hopping(NNNH) is to increase the period of the magnetic subbands in f/f0 from 1 to 6 (where f is the magnetic flux through a unit cell and f0 is the flux quanta). The shiftsof the energy levels due to the NNNH vary with the magnetic field. The Holmholtz free energy atthe points f/f0=6n+1 is lowered as compared to that with the nearest neighbor hopping only. Forgraphene nanoribbons, the magnetic susceptibility …