Publications by Emanuele Uccelli

Tuning the response of non-allowed Raman modes in GaAs nanowires

Anna Fontcuberta i Morral, Emanuele Uccelli, Gözde Tütüncüoglu, Esther Alarcon Llado, Federico Matteini, Francesca Amaduzzi, Hubert Hautmann

We report on the use of photonic resonances in Raman spectroscopy on single nanowires for the enhancement of forbidden modes and the study of the interaction of phonons with free-carriers. This is achieved by suspending nanowire over a trench and detecting ...

Iop Publishing Ltd2016

Charge carrier generation, relaxation, and recombination in polytypic GaAs nanowires studied by photoluminescence excitation spectroscopy

Pierre Michel Corfdir, Anna Fontcuberta i Morral, Emanuele Uccelli

We report results of a study of polytypic GaAs nanowires using low-temperature photoluminescence excitation spectroscopy. The nanowire ensemble shows a strong absorption at 1.517 eV, as a result of resonant generation of heavy-hole excitons in the zinc-ble ...

American Institute of Physics2013

Three-Dimensional Magneto-Photoluminescence as a Probe of the Electronic Properties of Crystal-Phase Quantum Disks in GaAs Nanowires

Pierre Michel Corfdir, Anna Fontcuberta i Morral, Emanuele Uccelli, Sonia Conesa Boj

Crystal-phase engineering has emerged as a novel method of bandgap engineering, made feasible by the high surface-to-volume ratio of nanowires. There remains intense debate about the exact characteristics of the band structure of the novel crystal phases, ...

Amer Chemical Soc2013

Exciton localization mechanisms in wurtzite/zinc-blende GaAs nanowires

Anna Fontcuberta i Morral, Martin Heiss, Emanuele Uccelli, Sonia Conesa Boj

We investigate the emission properties of excitons in GaAs nanowires containing quantum disks formed by structural alternation between the zinc-blende and wurtzite phases, by means of temperature-dependent photoluminescence. At 10 K the emission from an en ...

American Physical Society (APS)2013

Pressure Tuning of the Optical Properties of GaAs Nanowires

Anna Fontcuberta i Morral, Emanuele Uccelli

The tuning of the optical and electronic properties of semiconductor nanowires can be achieved by crystal phase engineering. Zinc-blende and diamond semiconductors exhibit pressure-induced structural transitions as well as a strong pressure dependence of t ...

American Chemical Society2012

Suppression of three dimensional twinning for a 100% yield of vertical GaAs nanowires on silicon

Anna Fontcuberta i Morral, Lionel Michelet, Martin Heiss, Emanuele Uccelli, Eleonora Russo

Multiple seed formation by three-dimensional twinning at the initial stages of growth explains the manifold of orientations found when self-catalyzed GaAs nanowires grow on silicon. This mechanism can be tuned as a function of the growth conditions by chan ...

2012

Mobility and carrier density in p-type GaAs nanowires measured by transmission Raman spectroscopy

Anna Fontcuberta i Morral, Bernt Ketterer, Emanuele Uccelli

Mobility and carrier density in p-type GaAs nanowires measured by transmission Raman spectroscopy ...

2012

Three-Dimensional Multiple-Order Twinning of Self-Catalyzed GaAs Nanowires on Si Substrates

François Morier-Genoud, Gabriel Mugny, Anna Fontcuberta i Morral, Martin Heiss, Emanuele Uccelli, Eleonora Russo

In this paper we introduce a new paradigm for nanowire growth that explains the unwanted appearance of parasitic nonvertical nanowires. With a crystal structure polarization analysis of the initial stages of GaAs nanowire growth on Si substrates, we demons ...

American Chemical Society2011

In(Ga)As quantum dot formation on group-III assisted catalyst-free InGaAs nanowires

Anna Fontcuberta i Morral, Martin Heiss, Bernt Ketterer, Emanuele Uccelli

Growth of GaAs and InxGa1-xAs nanowires by the group-III assisted molecular beam epitaxy growth method on (001)GaAs/SiO2 substrates is studied in dependence on growth temperature, with the objective of maximizing the indium incorporation. Nanowire growth w ...

Institute of Physics2011

Direct correlation of crystal structure and optical properties in wurtzite/zinc-blende GaAs nanowire heterostructures

Anna Fontcuberta i Morral, Martin Heiss, Emanuele Uccelli, Efthimios Kaxiras, Jun Ren, Sonia Conesa Boj

A method for the direct correlation at the nanoscale of structural and optical properties of single GaAs nanowires is reported. Nanowires consisting of 100% wurtzite and nanowires presenting zinc-blende/wurtzite polytypism are investigated by photoluminesc ...

2011

Untangling the Electronic Band Structure of Wurtzite GaAs Nanowires by Resonant Raman Spectroscopy

Anna Fontcuberta i Morral, Martin Heiss, Bernt Ketterer, Emanuele Uccelli

In semiconductor nanowires, the coexistence of wurtzite and zinc-blende phases enables the engineering of the electronic structure within a single material. This presupposes an exact knowledge of the band structure in the wurtzite phase. We demonstrate tha ...

American Chemical Society2011

Supercooling of nanoscale Ga drops with controlled impurity levels

Anna Fontcuberta i Morral, Emanuele Uccelli

We use in situ observations by variable temperature transmission electron microscopy on Ga drops at the tips of GaAs nanowires to investigate the phase behavior of nanoscale Ga. Experiments on pure Ga drops are compared with drops containing well-defined l ...

2011

InAs Quantum Dot Arrays Decorating the Facets of GaAs Nanowires

Anna Fontcuberta i Morral, Emanuele Uccelli

InAs quantum dot arrays are obtained on GaAs nanowire facets by molecular beam epitaxy. The GaAs nanowires are first grown by the gallium-assisted catalyst-free method. Decoration of the nanowire facets with InAs quantum dots is achieved only when the face ...

American Chemical Society2010

Compensation mechanism in silicon-doped gallium arsenide nanowires

Anna Fontcuberta i Morral, Bernt Ketterer, Emanuele Uccelli

P-type gallium arsenide nanowires were grown with different silicon doping concentrations. The incorporation is monitored by Raman spectroscopy of the local vibrational modes. For Si-concentrations up to 1.4 x 10(18) cm(-3), silicon incorporates mainly in ...

American Institute of Physics2010

Optical Properties of InAs Quantum Dot Array Ensembles with Predetermined Lateral Sizes from 20 to 40 nm

Anna Fontcuberta i Morral, Laura Waller, Emanuele Uccelli

Cleaved edge overgrowth and selective area epitaxy were combined for the synthesis of InAs quantum dot (QD) arrays with lateral sizes from 20 to 40 nm. The optical properties were locally assessed by confocal photoluminescence spectroscopy experiments at l ...

2010

Thermal conductivity of GaAs nanowires studied by micro-Raman spectroscopy combined with laser heating

Anna Fontcuberta i Morral, Emanuele Uccelli

The thermal properties of freely suspended GaAs nanowires are investigated by applying a method which relies on laser heating and the determination of the local temperature by Raman spectroscopy. In order to determine the values for the thermal conductivit ...

American Institute of Physics2010

P-Doping Mechanisms in Catalyst-Free Gallium Arsenide Nanowires

Anna Fontcuberta i Morral, Carlo Colombo, Tonko Garma, Bernt Ketterer, Emanuele Uccelli, Marco Nicotra

Doped catalyst-free GaAs nanowires have been grown by molecular beam epitaxy with the gallium-assisted method. The spatial dependence of the dopant concentration and resistivity have been measured by Raman spectroscopy and four point electrical measurement ...

American Chemical Society2010

A level set simulation for ordering of quantum dots via cleaved-edge overgrowth

Anna Fontcuberta i Morral, Emanuele Uccelli

Cleaved-edge overgrowth (CEO) is a promising technique to obtain ordered arrays of quantum dots, where the size and position of the dots can be controlled very well. We present level set simulations for CEO. Our simulations illustrate how the quality of th ...

American Institute of Physics2009

Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

Anna Fontcuberta i Morral, Emanuele Uccelli

A contacting scheme to measure the transport properties into self-assembled InAs Quantum Wires (QWRs) or Quantum Dots (QDs) is presented. The nanostructures are formed on the (110) cleaved edge of a AlAs/AlGaAs heterostructure substrate by means of the Cle ...

Wiley2009