References of "Zanolli, Zeila"
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See detailElectric control of the magnetization in BiFeO3/LaFeO3 superlattices
Zanolli, Zeila ULg; Wojdeł, Jacek; Iniguez, Jorge et al

in Physical Review B (2013), 88

First-principles techniques are used to investigate the behavior of BiFeO3/LaFeO3 perovskite oxide superlattices epitaxially grown on a (001)-SrTiO3 substrate. The calculations show that 1/1 superlattices ... [more ▼]

First-principles techniques are used to investigate the behavior of BiFeO3/LaFeO3 perovskite oxide superlattices epitaxially grown on a (001)-SrTiO3 substrate. The calculations show that 1/1 superlattices exhibit a Pmc21 ground state combining a trilinear coupling of one polar and two oxygen rotational lattice modes, and weak ferromagnetism. The microscopic mechanism allowing one to manipulate the magnetization with an electric field in such systems is presented and its dependence on strain and chemical substitution is discussed. BiFeO3/LaFeO3 artificial superlattices appear to be good candidates to achieve electric switching of magnetization at room temperature. [less ▲]

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See detailGas Sensing with Au-Decorated Carbon Nanotubes
Zanolli, Zeila ULg; Leghrib, Radouane; Felten, Alexandre et al

in ACS Nano (2011), 5(6), 4592-4599

The sensing properties of carbon nanotubes (CNTs) decorated with gold nanopar- ticles have been investigated by means of combined theoretical and experimental approaches. On one hand, first-principles and ... [more ▼]

The sensing properties of carbon nanotubes (CNTs) decorated with gold nanopar- ticles have been investigated by means of combined theoretical and experimental approaches. On one hand, first-principles and nonequilibrium Green's functions techniques give access to the microscopic features of the sensing mechanisms in individual nanotubes, such as electronic charge transfers and quantum conductances. On the other hand, drop coating deposition of carbon nanotubes decorated with gold nanoparticles onto sensor substrates and their characterization in the detection of pollutants such as NO2, CO, and C6H6 provide insight into the sensing ability of nanotube mats. Using the present combined approaches, the improvement in the detection of some specific gases (NO2 and CO) using Au-functionalized nanotubes is explained. However, for other gases such as C6H6, the Au nanoparticles do not seem to play a crucial role in the sensing process when compared with pristine CNTs functionalized with oxygen plasma. Indeed, these different situations can be explained by identifying the relationship between the change of resistance (macroscopic feature) and the shift of the Fermi level (microscopic feature) after gas adsorption. The understanding of the sensing ability at the atomic level opens the way to design new gas sensors and to tune their selectivity by predicting the nature of the metal that is the most appropriate to detect specific molecular species. [less ▲]

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See detailGrowth of Straight InAs-on-GaAs Nanowire Heterostructures
Messing, Maria E; Wong-Leung, Jennifer; Zanolli, Zeila ULg et al

in Nano Letters (2011), 11(9), 3899-3905

One of the main motivations for the great interest in semiconductor nanowires is the possibility of easily growing advanced heterostructures that might be difficult or even impossible to achieve in thin ... [more ▼]

One of the main motivations for the great interest in semiconductor nanowires is the possibility of easily growing advanced heterostructures that might be difficult or even impossible to achieve in thin films. For III␣V semiconductor nanowires, axial heterostructures with an interchange of the group III element typically grow straight in only one interface direction. In the case of InAs␣GaAs heterostructures, straight nanowire growth has been demonstrated for growth of GaAs on top of InAs, but so far never in the other direction. In this article, we demonstrate the growth of straight axial heterostructures of InAs on top of GaAs. The heterostructure interface is sharp and we observe a dependence on growth parameters closely related to crystal structure as well as a diameter dependence on straight nanowire growth. The results are discussed by means of accurate first principles calculations of the inter- facial energies. In addition, the role of the gold seed particle, the effect of its composition at different stages during growth, and its size are discussed in relation to the results observed. [less ▲]

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See detailSpin transport in carbon nanotubes with magnetic vacancy-defects
Zanolli, Zeila ULg; Charlier, Jean-Christophe

in Physical Review. B, Condensed Matter and Materials Physics (2010), 81(16),

The spin-polarized electron transport properties of metallic carbon nanotubes containing vacancies are investigated using first-principles and nonequilibrium Green’s function techniques. Reconstructed ... [more ▼]

The spin-polarized electron transport properties of metallic carbon nanotubes containing vacancies are investigated using first-principles and nonequilibrium Green’s function techniques. Reconstructed mono- and trivacancies, containing carbon atoms with unsaturated bonds, behave like quasilocalized magnetic impurities. However, in conventional ab initio simulations, these magnetic defects are artificially repeated periodically (supercell method) and are thus incorrectly coupled by long range interactions. Consequently, a technique based on an open system with an isolated magnetic impurity is used here to accurately describe the local magnetic properties of these defects, revealing spin-dependent conductances in tubes, which could be exploited in spintronic nanodevices. [less ▲]

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See detailQuantum Spin Transport in Carbon Chains
Zanolli, Zeila ULg; Onida, Giovanni; Charlier, Jean-Christophe

in ACS Nano (2010), 4(9), 5174-5180

First-principles and non-equilibrium Green’s function approaches are used to predict spin-polarized electronic transport in monatomic carbon chains covalently connected to graphene nanoribbons, as ... [more ▼]

First-principles and non-equilibrium Green’s function approaches are used to predict spin-polarized electronic transport in monatomic carbon chains covalently connected to graphene nanoribbons, as recently synthetized experimentally (Jin, C.; et al. Phys. Rev. Lett. 2009, 102, 205501−205504). Quantum electron conductances exhibit narrow resonant states resulting from the simultaneous presence of open conductance channels in the contact region and on the chain atoms. Odd-numbered chains, which acquire metallic or semiconducting character depending on the nature of the edge at the graphene contact, always display a net spin polarization. The combination of electrical and magnetic properties of chains and contacts results in nanodevices with intriguing spintronic properties such as the coexistence of magnetic and semiconducting behaviors. [less ▲]

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See detailNO2 and CO interaction with plasma treated Au-decorated MWCNTs: Detection pathways
Leghrib, R.; Llobet, E.; Felten, A. et al

in Procedia Chemistry (2009), 1(1), 931-934

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See detailCarbon nanotubes randomly decorated with gold clusters: from nano(2)hybrid atomic structures to gas sensing prototypes
Charlier, Jean-Christophe; Arnaud, L.; Avilov, I. V. et al

in Nanotechnology (2009), 20(37),

Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition ... [more ▼]

Carbon nanotube surfaces, activated and randomly decorated with metal nanoclusters, have been studied in uniquely combined theoretical and experimental approaches as prototypes for molecular recognition. The key concept is to shape metallic clusters that donate or accept a fractional charge upon adsorption of a target molecule, and modify the electron transport in the nanotube. The present work focuses on a simple system, carbon nanotubes with gold clusters. The nature of the gold–nanotube interaction is studied using first-principles techniques. The numerical simulations predict the binding and diffusion energies of gold atoms at the tube surface, including realistic atomic models for defects potentially present at the nanotube surface. The atomic structure of the gold nanoclusters and their effect on the intrinsic electronic quantum transport properties of the nanotube are also predicted. Experimentally, multi-wall CNTs are decorated with gold clusters using (1) vacuum evaporation, after activation with an RF oxygen plasma and (2) colloid solution injected into an RF atmospheric plasma; the hybrid systems are accurately characterized using XPS and TEM techniques. The response of gas sensors based on these nano2hybrids is quantified for the detection of toxic species like NO2, CO, C2H5OH and C2H4. [less ▲]

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See detailDefective carbon nanotubes for single-molecule sensing
Zanolli, Zeila ULg; Charlier, Jean-Christophe

in Physical Review. B, Condensed Matter and Materials Physics (2009), 80(15),

The sensing ability of metallic carbon nanotubes toward various gas species (NO2, NH3, CO, H2O, and CO2) is investigated via ab initio calculations and Nonequilibrium Green’s Functions technique, focusing ... [more ▼]

The sensing ability of metallic carbon nanotubes toward various gas species (NO2, NH3, CO, H2O, and CO2) is investigated via ab initio calculations and Nonequilibrium Green’s Functions technique, focusing on the salient features of the interaction between molecules and oxygenated-defective tubes. As the adsorption/desorption of molecules induces modulations on the electrical conductivity of the tube, the computation of the electron quantum conductance can be used to predict gas detection. Indeed, the analysis of the conductance curve in a small energy range around the Fermi energy reveal that oxygenated-defective nanotubes are sensitive to NO2, NH3, CO, and H2O, but not to CO2. Molecular selectivity can also be provided by the nature of the charge transfer. [less ▲]

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See detailElectronic properties and quantum transport in Graphene-based nanostructures
Dubois, Simon; Zanolli, Zeila ULg; Declerck, Xavier et al

in European Physical Journal B -- Condensed Matter (2009), 72(1), 1-24

Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) represent a novel class of low-dimensional materials. All these graphene-based nanostructures are expected to display the extraordinary electronic ... [more ▼]

Carbon nanotubes (CNTs) and graphene nanoribbons (GNRs) represent a novel class of low-dimensional materials. All these graphene-based nanostructures are expected to display the extraordinary electronic, thermal and mechanical properties of graphene and are thus promising candidates for a wide range of nanoscience and nanotechnology applications. In this paper, the electronic and quantum transport properties of these carbon nanomaterials are reviewed. Although these systems share the similar graphene electronic structure, confinement effects are playing a crucial role. Indeed, the lateral confinement of charge carriers could create an energy gap near the charge neutrality point, depending on the width of the ribbon, the nanotube diameter, the stacking of the carbon layers regarding the different crystallographic orientations involved. After reviewing the transport properties of defect-free systems, doping and topological defects (including edge disorder) are also proposed as tools to taylor the quantum conductance in these materials. Their unusual electronic and transport properties promote these carbon nanomaterials as promising candidates for new building blocks in a future carbon-based nanoelectronics, thus opening alternatives to present silicon-based electronics devices. [less ▲]

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See detailExperimental and theoretical studies suggesting the possibility of metallic boron nitride edges in porous nanourchins
Terrones, M.; Charlier, Jean-Christophe; Gloter, A. et al

in Nano Letters (2008), 8(4), 1026-1032

We first describe the synthesis of novel and highly porous boron nitride (BN) nanospheres (100–400 nm o.d.) that exhibit a rough surface consisting of open BN nanocones and corrugated BN ribbons. The ... [more ▼]

We first describe the synthesis of novel and highly porous boron nitride (BN) nanospheres (100–400 nm o.d.) that exhibit a rough surface consisting of open BN nanocones and corrugated BN ribbons. The material was produced by reacting B2O3 with nanoporous carbon spheres under nitrogen at ca. 1750 °C. The BN nanospheres were characterized using scanning electron microscopy, high-resolution electron microscopy, and electron energy loss spectroscopy. The porous BN spheres show relatively large surface areas of ca. 290 m2/g and exhibit surprisingly stable field emission properties at low turn-on voltages (e.g., 1–1.3 V/µm). We attribute these outstanding electron emission properties to the presence of finite BN ribbons located at the surface of the nanospheres (exhibiting zigzag edges), which behave like metals as confirmed by first-principles calculations. In addition, our ab initio theoretical results indicate that the work function associated to these zigzag BN ribbons is 1.3 eV lower when compared with BN-bulk material. [less ▲]

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See detailSize-selected compound semiconductor quantum dots by nanoparticle conversion
Wacaser, Brent A; Dick, Kimberly A; Zanolli, Zeila ULg et al

in Nanotechnology (2007), 18(10),

We have developed a novel technology, called nanoparticle conversion, for producing compound semiconductor quantum dots (QDs) in which the dot size, surface density, position, and the materials system are ... [more ▼]

We have developed a novel technology, called nanoparticle conversion, for producing compound semiconductor quantum dots (QDs) in which the dot size, surface density, position, and the materials system are all independently controlled. Nanoparticle conversion also lends itself to spatially controlled positioning of QDs. To demonstrate this technology we report the formation of InP QDs using nanoparticle conversion. We have produced QDs on substrates of different types by converting randomly and lithographically positioned nanoparticles into compound semiconductors in a chemical vapour deposition system. Electron microscopy and atomic force microscopy measurements reveal that the morphology of these QDs is similar to that of QDs produced by other techniques. Photo- and cathodoluminescence measurements show that the converted nanoparticles exhibit properties and behaviours typical of semiconductor QDs. These include quantum confinement, free-to-bound recombination and blinking. Production of multi-component QDs like InP, GaN, and InAsP on various substrates like Si, SiO2, and sapphire show that this technology can produce a wide variety of different types of QD on different substrates with minimal need for process optimization. [less ▲]

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See detailCore-shell InP-CdS nanowires: fabrication and study
Zanolli, Zeila ULg; Wacaser, Brent A; Pistol, Mats-Erik et al

in Journal of Physics : Condensed Matter (2007), 19(29),

InP nanowires are fabricated by organo-metallic vapour phase epitaxy and studied via photoluminescence measurements performed on single nanowires, finding evidence of state filling with increasing ... [more ▼]

InP nanowires are fabricated by organo-metallic vapour phase epitaxy and studied via photoluminescence measurements performed on single nanowires, finding evidence of state filling with increasing excitation power density. To increase flexibility in fabrication technology we developed a wet chemical procedure to grow a CdS shell on these wires. In these InP–CdS wires the luminescence efficiency was decreased with respect to the bare wires. The CdS capping procedure needs further investigations to improve the emission properties of nanowires, in order to become technically useful. We suggest as possible improvements of this technique to increase the bath temperature and/or illuminate the sample with UV radiation during the capping procedure. [less ▲]

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See detailQuantum-confinement effects in InAs-InP core-shell nanowires
Zanolli, Zeila ULg; Pistol, Mats-Eric; Froberg, Linus E et al

in Journal of Physics : Condensed Matter (2007), 19(29),

We report the detection of quantum confinement in single InAs–InP core–shell nanowires. The wires, having an InAs core with ~25 nm diameter, are characterized by emission spectra in which two peaks are ... [more ▼]

We report the detection of quantum confinement in single InAs–InP core–shell nanowires. The wires, having an InAs core with ~25 nm diameter, are characterized by emission spectra in which two peaks are identified under high excitation intensity conditions. The peaks are caused by emission from the ground and excited quantized levels, due to quantum confinement in the plane perpendicular to the nanowire axis. We have identified different energy contributions in the emission spectra, related to the wurtzite structure of the wires, the strain between the wurtzite core and the shell, and the confinement energy of the InAs core. Calculations based on six-band strain-dependent theory allow the theoretical estimation of the confined energy states in such materials, and we found these results to be in good agreement with those from the photoluminescence studies. [less ▲]

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See detailModel GW band structure of InAs and GaAs in the wurtzite phase
Zanolli, Zeila ULg; Fuchs, F.; Furthmueller, J. et al

in Physical Review. B, Condensed Matter and Materials Physics (2007), 75(24),

We report quasiparticle calculations of the newly observed wurtzite polymorph of InAs and GaAs. The calculations are performed in the GW approximation (based on a model dielectric function) using plane ... [more ▼]

We report quasiparticle calculations of the newly observed wurtzite polymorph of InAs and GaAs. The calculations are performed in the GW approximation (based on a model dielectric function) using plane waves and pseudopotentials. For comparison we also report the study of the zinc-blende phase within the same approximations. In the InAs compound the In 4d electrons play a very important role: whether they are frozen in the core or not leads either to a correct or a wrong band ordering (negative gap) within the local-density appproximation (LDA). We have calculated the GW band structure in both cases. In the first approach, we have estimated the correction to the pd repulsion calculated within the LDA and included this effect in the calculation of the GW corrections to the LDA spectrum. In the second case, we circumvent the negative gap problem by first using the screened exchange approximation and then calculating the GW corrections starting from the so obtained eigenvalues and eigenfunctions. This approach, that can be thought of as a step towards self-consistency, leads to a more realistic band structure and was also used for GaAs. For both InAs and GaAs in the wurtzite phase we predict an increase of the quasiparticle gap with respect to the zinc-blende polytype. [less ▲]

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See detailInAs with wurtzite crystal structure: full-potential and psedopotential ab-initio calculations
Zanolli, Zeila ULg; von Barth, Ulf

in Luitz, Joachim; Hebert, Cecile; Weinmeier, Kerstin (Eds.) et al DFTEM2006 - bringing together two communities (2006)

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See detailFabrication, optical characterization and modeling of strained core-shell nanowires
Zanolli, Zeila ULg; Froberg, Linus E; Bjork, M. T. et al

in Thin Solid Films (2006), 515(2), 793-796

Strained nanowires with varying InAs/InP core/shell thicknesses were grown using Chemical Beam Epitaxy. Microphotoluminescence spectroscopy, performed at low temperature, was then used to study the ... [more ▼]

Strained nanowires with varying InAs/InP core/shell thicknesses were grown using Chemical Beam Epitaxy. Microphotoluminescence spectroscopy, performed at low temperature, was then used to study the optical properties of single wires. Emission from the InAs core was observed and its dependence on the shell thickness / core diameter ratio was investigated. We found that it is possible to tune the emission energy towards 0.8 eV by controlling this ratio. We have compared the measured energies with calculated energies. Our findings are consistent with the wires having a hexagonal crystal structure. [less ▲]

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See detailState of the art of InP and GaAs quantum cascade lasers
Scamarcio, Gaetano; Spagnolo, Vincenzo; Troccoli, Mariano et al

in IEEE International Conference on Indium Phosphide & Related Materials (IPRM) (2002)

The key physical phenomena associated with long-wavelength infrared emission and laser action in quantum cascade lasers based on InP/GaInAs/AlInAs and GaAs/AlGaAs heterostructures are reviewed. The effect ... [more ▼]

The key physical phenomena associated with long-wavelength infrared emission and laser action in quantum cascade lasers based on InP/GaInAs/AlInAs and GaAs/AlGaAs heterostructures are reviewed. The effect of different tunnel injection schemes on the hot-electron energy distributions is compared. High-power superlattice lasers with improved high-energy injection schemes are described. The local temperature distribution, the thermal resistance and the hot-phonon effects are monitored in operating devices by micro-probe Raman and luminescence measurements. [less ▲]

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See detailGaAs-based Quantum Cascade Lasers: design, fabrication and perspective.
Zanolli, Zeila ULg; Scamarcio, Gaetano; Rizzi, Francesco et al

(2002)

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