Abstract: Density-functional theory in combination with the nonequilibrium Green's function formalism is used to study the effect of substitutional doping on the electronic transport properties of hydrogen passivated zig-zag graphene nanoribbon devices. B, N and Si atoms are used to substitute carbon atoms located at the center or at the edge of the sample. We found that Si -doping results in better electronic transport as compared to the other substitutions. The transmission spectrum also depends on the location of the substitutional dopants: for single atom doping the largest transmission is obtained for edge substitutions, whereas substitutions in the middle of the sample give larger transmission for double carbon substitutions. The obtained results are explained in terms of electron localization in the system due to the presence of impurities. (C) 2016 Elsevier B.V. All rights reserved.

Abstract: The effects due to intersubband coupling and screening on the ionized impurity scattering are studied for a quasi-two-dimensional electron system in delta-doped semiconductors. We found that intersubband coupling plays an essential role in describing the screening properties and the effect of ionized impurity scattering on the mobility in a multisubband system. At the onset of the occupation of a higher subband, the screening due to the intersubband coupling leads to a reduction of the small angle scattering rate in the lower subband. We showed that such an effect is significant in a delta-doped quantum well and results in a pronounced increase of the quantum mobility at the onset of the occupation of a higher subband. (C) 1996 American Institute of Physics.

Abstract: The electronic structure of the conduction and valence bands of a quantum ring containing a layer inside the ring opening is modeled This structure (nanocup) consists of a GaAs nanodisk (the cup s bottom) and a GaAs nanoring (the cup s rim) which encircles the disk The whole system is embedded in an (Al Ga)As matrix and its shape resembles realistic ring structures grown by the droplet epitaxy technique The conduction-band states in the structure are modeled by the single-band effective-mass theory while the 4-band Luttinger-Kohn model is adopted to compute the valence-band states We analyze how the electronic structure of the nanocup evolves from the one of a quantum ring when the size of either the nanodisk or the nanoring is changed For that purpose (1) the width of the ring (2) the disk radius and (3) the disk height are separately varied For dimensions typical for experimentally realized structures we find that the electron wavefunctions are mainly localized inside the ring even when the thickness of the Inner layer is 90% of the ring thickness These calculations indicate that topological phenomena like the excitonic Aharonov-Bohm effect are negligibly affected by the presence of the layer inside the ring (C) 2010 Elsevier Ltd All rights reserved

Abstract: We report on magnetisation of individual superconducting particles with size down to 0.1 micron. The non-invasive access to properties of such small objects has become possible using submicron Hall probes which detect a local magnetic field and work effectively as micro-fluxmeters similar to, e.g., SQUIDs but with an effective detection loop of only about a square micron. We have found that the spatial confinement of superconductivity in a small volume gives rise to dramatic changes in thermodynamic properties of mesoscopic superconductors. (C) 1998 Academic Press Limited.

Abstract: We investigate the effects of the finite confining potential V0 on the absorption and emission scattering rates of electrons interacting with LO phonons for a cylindrical GaAs quantum wire. The emission rates are qualitatively similar to those of the 2D case. The absorption rates on the other hand exhibit two different regimes: 1) for a wire radius smaller than a certain value (80 Å in the case where V0 = 190 meV) the behavior is similar to the 2D and 3D analogues, but 2) for larger radius the absorption rates initially increase with increasing energy, reach a maximum value and then decrease monotonicaly. A complete study is made as a function of wire radius, and electron energy.