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Full-Text Articles in Engineering
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.
Low Temperature Graphene Growth, Shailesh Kumar, N Mcevoy, T. Lutz, G. Keeley, Nicholas Whiteside, Werner Blau, G. Duesberg
Low Temperature Graphene Growth, Shailesh Kumar, N Mcevoy, T. Lutz, G. Keeley, Nicholas Whiteside, Werner Blau, G. Duesberg
Faculty of Engineering and Information Sciences - Papers: Part A
We demonstrate the growth of graphene films on nickel substrates by chemical vapour deposition using acetylene at temperatures as low as 750 degrees celsius, opening a viable route for its scalable production. Raman spectroscopy was used to confirm defect-free mono and multilayer graphene at and above this temperature, and of defective graphene at lower temperatures. Atomic force microscopy and scanning electron microscopy performed directly on the films give an indication of graphene flake size, morphology and also the topography on substrate. An unexpected dependence of graphene thickness on precursor dwell time is reported. This together with low temperature growth suggests …
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.
Identification Of Multiple Oscillation States Of Carbon Nanotube Tipped Cantilevers Interacting With Surfaces In Dynamic Atomic Force Microscopy, Mark Strus, Arvind Raman
Identification Of Multiple Oscillation States Of Carbon Nanotube Tipped Cantilevers Interacting With Surfaces In Dynamic Atomic Force Microscopy, Mark Strus, Arvind Raman
Birck and NCN Publications
Carbon nanotubes (CNTs) have gained increased interest in dynamic atomic force microscopy (dAFM) as sharp, flexible, conducting, nonreactive tips for high-resolution imaging, oxidation lithography, and electrostatic force microscopy. By means of theory and experiments we lay out a map of several distinct tapping mode AFM oscillation states for CNT tipped AFM cantilevers: namely, noncontact attractive regime oscillation, intermittent contact with CNT slipping or pinning, or permanent contact with the CNT in point or line contact with the surface while the cantilever oscillates with large amplitude. Each state represents fundamentally different origins of CNT-surface interactions, CNT tip-substrate dissipation, and phase contrast …