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Anna Fontcuberta i Morral

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Related publications (286)

Synthesis parameter space of bismuth catalyzed germanium nanowires

The synthesis parameter space of bismuth catalyzed germanium nanowires by chemical vapor deposition is determined. The process window for high aspect ratio nanowires is found to be extremely narrow. The optimal conditions are found to be 300 degrees C and ...

American Institute of Physics2009

Gallium arsenide p-i-n radial structures for photovoltaic applications

Michael Graetzel, Anna Fontcuberta i Morral, Carlo Colombo, Martin Heiss

Gallium arsenide p-i-n radial junctions were fabricated by molecular beam epitaxy. The current-voltage characteristics of single nanowires were measured in the dark and under various illumination conditions including 1.5 AM. The total efficiency was 4.5%. ...

American Institute of Physics2009

Single crystalline and core-shell indium-catalyzed germanium nanowires-a systematic thermal CVD growth study

Anna Fontcuberta i Morral, Martin Heiss, Sonia Conesa Boj

Germanium nanowires were synthesized using thermal chemical vapor deposition (CVD) and indium as a catalyst. The process parameter space for successful growth was studied. By optimizing the growth temperature and gas pressure, high aspect ratio germanium n ...

Institute of Physics2009

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

Photocurrent and photoconductance properties of a GaAs nanowire

Anna Fontcuberta i Morral

We report on photocurrent and photoconductance processes in a freely suspended p-doped single GaAs nanowire. The nanowires are grown by molecular beam epitaxy, and they are electrically contacted by a focused ion beam deposition technique. The observed pho ...

American Institute of Physics2009

A micron‐sized nanoporous multifunction sensing device

Anna Fontcuberta i Morral

In this work, a capacitive sensor based on Anodic Aluminium Oxide (AAO) porous structures has been developed. In some cases, the pores have been also conformally coated with a high chemical pure SiO2 by means of Atomic Layer Deposition (ALD). Temperature m ...

Wiley2009

(S)TEM tomography of AlAs-GaAs coaxial Nanowires

Anna Fontcuberta i Morral

(S) TEM tomography is used as a complementary tool to characterize AlAs-GaAs coaxial nanowires. These nanostructures have been grown on two different GaAs substrate orientations using molecular-beam epitaxy (MBE). The results show that quantum wells synthe ...

IEEE2009

Long range epitaxial growth of prismatic heterostructures on the facets of catalyst-free GaAs nanowires

Anna Fontcuberta i Morral, Sonia Conesa Boj

Molecular beam epitaxy is used for the synthesis of catalyst-free GaAs nanowires and related quantum heterostructures. After growth of the nanowire GaAs core, the conditions are changed in situ towards standard MBE planar growth in order to obtain quantum ...

Royal Society of Chemistry2009

Gallium assisted plasma enhanced chemical vapor deposition of silicon nanowires

Anna Fontcuberta i Morral, Libo Yu, Sonia Conesa Boj, Père Roca i Cabarrocas

Silicon nanowires have been grown with gallium as catalyst by plasma enhanced chemical vapor deposition. The morphology and crystalline structure has been studied by electron microscopy and Raman spectroscopy as a function of growth temperature and catalys ...

Institute of Physics2009

Catalyst-free nanowires with axial InxGa1-xAs/GaAs heterostructures

Anna Fontcuberta i Morral, Martin Heiss, Sonia Conesa Boj

Self-catalyzed growth of axial InxGa1-xAs/GaAs heterostructures has been realized by molecular beam epitaxy. The growth of the wires is achieved from gallium/indium alloy droplets that are nucleated in situ. By variation of the In/Ga beam flux during the g ...

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

De Haas-van Alphen effect and energy gaps of a correlated two-dimensional electron system in an AlAs two-valley pseudospin system

Anna Fontcuberta i Morral, Dirk Grundler

We report highly sensitive de Haas-van Alphen (dHvA) effect measurements on a high-mobility two-dimensional electron system in an AlAs quantum well. Here two valleys are occupied forming a pseudospin system. At 400 mK, the dHvA effect shows pronounced osci ...

2009

General theoretical considerations on nanowire solar cell designs

Anna Fontcuberta i Morral

We propose two novel solar cell designs, tapping the advantages of semiconductor nanowires. A silicon (Si) tandem cell can be achieved by growing sub-5 nm p-n junction in the radial direction of the Si nanowires on a planar crystalline Si cell. For series ...

Wiley2009

Imaging of GaAs Nanowire Using Combined Aberration-corrected TEM/STEM and Exit Wave Restoration

Cécile Hébert, Anna Fontcuberta i Morral

2009

Shadow modulated two-dimensional heterostructures using vertical pillars

Anna Fontcuberta i Morral

A vertical pillar shadow epitaxy technique is introduced for fabricating coplanar striped or cross-hatched GaAsAlAs two-dimensional heterostructures, where the pattern area of each individual layer can be varied in situ. An array of vertical pillars is mou ...

2008

Influence of the (111) twinning on the formation of diamond cubic/diamond hexagonal heterostructures in Cu-catalyzed Si nanowires

Anna Fontcuberta i Morral, Père Roca i Cabarrocas

The occurrence of heterostructures of cubic silicon/hexagonal silicon as disks defined along the nanowire < 111 > growth direction is reviewed in detail for Si nanowires obtained using Cu as catalyst. Detailed measurements on the structural properties of b ...

American Institute of Physics2008

Size and environment dependence of surface phonon modes of gallium arsenide nanowires as measured by Raman spectroscopy

Anna Fontcuberta i Morral

Gallium arsenide nanowires were synthesized by gallium-assisted molecular beam epitaxy. By varying the growth time, nanowires with diameters ranging from 30 to 160 nm were obtained. Raman spectra of the nanowire ensembles were measured. The small linewidth ...

2008

Microstructured Horizontal Alumina Pore Arrays as Growth Templates for Large Area Few and Single Nanowire Devices

Anna Fontcuberta i Morral

We demonstrate the fabrication of horizontally aligned and well-defined nanopore structures by anodic oxidation of aluminum thin films and micro stripes on a Si substrate. We are able to control both, the pore diameters and interpore distances from 10 rim ...

WILEY-V C H VERLAG GMBH2008

Prismatic quantum heterostructures synthesized on molecular-beam epitaxy GaAs nanowires

Anna Fontcuberta i Morral

Wiley-Blackwell2008

Nucleation mechanism of gallium-assisted molecular beam epitaxy growth of gallium arsenide nanowires

Anna Fontcuberta i Morral, Carlo Colombo

Molecular beam epitaxy Ga-assisted synthesis of GaAs nanowires is demonstrated. The nucleation and growth are seen to be related to the presence of a SiO2 layer previously deposited on the GaAs wafer. The interaction of the reactive gallium with the SiO2 p ...

American Institute of Physics2008

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