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Comment: 8 pages, 4 figures; Nano Letters, Publication Date (Web): Oct. 25 2011, http://pubs.acs.org/doi/abs/10.1021/nl202725w
Comment: 7 pages, 5 figures; v2. added results for noncompact gauge action; v3. added results for stout smearing, corrected rescaling of coupling, published version
The quasiparticle band gaps of semiconducting carbon nanotubes (CNTs) supported on a weakly-interacting hexagonal boron nitride (h-BN) substrate are computed using density functional theory and the GW Approximation. We find that the direct band gaps of the (7,0), (8,0) and (10,0) carbon nanotubes are renormalized to smaller values in the presence of the dielectric h-BN substrate. The decrease in the band gap is the result of a polarization-induced screening effect, which alters the correlation energy of the frontier CNT orbitals and stabilizes valence band maximum and conduction band minimum. The value of the band gap renormalization is on the order of 0.25 to 0.5 eV in each case. Accounting for polarization-induced band gap changes is crucial in comparing computed values with experiment, since nanotubes are almost always grown on subs...
Accurate modeling of the ␣-bands of armchair graphene nanoribbons (AGNRs) requires correctly reproducing asymmetries in the bulk graphene bands as well as providing a realistic model for hydrogen passivation of the edge atoms. The commonly used single-pz orbital approach fails on both these counts. To overcome these failures we introduce a nearest-neighbor, three orbital per atom p/d tight-binding model for graphene. The parameters of the model are fit to first-principles density-functional theory (DFT) – based calculations as well as to those based on the many-body Green’s function and screened-exchange (GW) formalism, giving excellent agreement with the ab initio AGNR bands. We employ this model to calculate the current-voltage characteristics of an AGNR MOSFET and the conductance of rough-edge AGNRs, finding significant differences ...
We demonstrate a novel chemical-free water-based technique to synthesize various forms of cuprous oxide nanostructures at room temperature. The self-assemblies of these nanostructures are formed by the anodic oxidation of Cu in deionized (DI) water. Direct growth of these nanostructures on SiO2/Si (100) substrate has been successfully achieved by tuning the bias voltage and the growth duration. A variety of nanostructures from one-dimensional nanowires to different complex two- and three-dimensional structures are successfully grown by this method. We show that the morphological evolution in the self-assembly of the structures strongly depends on the spatial electric field distribution on the substrate. Furthermore, the electrical devices made from these nanowire networks exhibit promising photon sensing characteristics under white lig...
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