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175 results on '"Franciosi, Alfonso"'

1. A Roadmap for Controlled and Efficient n-type Doping of Self-assisted GaAs Nanowires Grown by Molecular Beam Epitaxy

Author

Orrù, Marta, Repiso, Eva, Carapezzi, Stefania, Henning, Alex, Roddaro, Stefano, Franciosi, Alfonso, Rosenwaks, Yossi, Cavallini, Anna, Martelli, Faustino, and Rubini, Silvia

Subjects
Condensed Matter - Materials Science, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

N-type doping of GaAs nanowires has proven to be difficult because the amphoteric character of silicon impurities is enhanced by the nanowire growth mechanism and growth conditions. The controllable growth of n-type GaAs nanowires with carrier density as high as 1020 electron/cm3 by self-assisted molecular beam epitaxy using Te donors is demonstrated here. Carrier density and electron mobility of highly doped nanowires are extracted through a combination of transport measurement and Kelvin probe force microscopy analysis in single-wire field-effect devices. Low-temperature photoluminescence is used to characterize the Te-doped nanowires over several orders of magnitude of the impurity concentration. The combined use of those techniques allows the precise definition of the growth conditions required for effective Te incorporation.

Published
2021
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3. de Gennes-Saint-James resonant transport in Nb/GaAs/AlGaAs heterostructures

Author

Giazotto, Francesco, Pingue, Pasqualantonio, Beltram, Fabio, Lazzarino, Marco, Orani, Daniela, Rubini, Silvia, and Franciosi, Alfonso

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Resonant transport is demonstrated in a hybrid superconductor-semiconductor heterostructure junction grown by molecular beam epitaxy on GaAs. This heterostructure realizes the model system introduced by de Gennes and Saint-James in 1963 [P. G. de Gennes and D. Saint-James, Phys. Lett. {\bf 4}, 151 (1963)]. At low temperatures a single marked resonance peak is shown superimposed to the characteristic Andreev-dominated subgap conductance. The observed magnetotransport properties are successfully analyzed within the random matrix theory of quantum transport, and ballistic effects are included by directly solving the Bogoliubov-de Gennes equations., Comment: 10 pages, 5 figures, to be published in Phys. Rev. Lett

Published
2001

4. Reflectionless tunneling in planar Nb/GaAs hybrid junctions

Author

Giazotto, Francesco, Cecchini, Marco, Pingue, Pasqualantonio, Beltram, Fabio, Lazzarino, Marco, Orani, Daniela, Rubini, Silvia, and Franciosi, Alfonso

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Reflectionless-tunneling was observed in Nb/GaAs superconductor/semiconductor junctions fabricated through a two-step procedure. First, periodic $\delta$-doped layers were grown by molecular beam epitaxy near the GaAs surface, followed by an As cap layer to protect the surface during {\it ex-situ} transfer. Second, Nb was deposited by dc-magnetron sputtering onto the GaAs(001) 2 $\times$ 4 surface {\it in-situ} after thermal desorption of the cap layer. The magnetotransport behavior of the resulting hybrid junctions was successfully analyzed within the random matrix theory of phase-coherent Andreev transport. The impact of junction morphology on reflectionless tunneling and the applicability of the fabrication technique to the realization of complex superconductor/semiconductor mesoscopic systems are discussed., Comment: 10 pages, 3 figures, to be published in Appl. Phys. Lett

Published
2001
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5. 1.26 $\mu$m intersubband transitions in In$_{0.3}$Ga$_{0.7}$As/AlAs quantum wells

Author

Garcia, Cesar Pascual, De Nardis, Andrea, Pellegrini, Vittorio, Jancu, Jean Marc, Beltram, Fabio, Mueller, Bernhard H., Sorba, Lucia, and Franciosi, Alfonso

Subjects
Condensed Matter - Materials Science
Abstract

We observed room-temperature intersubband transitions at 1.26 microns in n-doped type-II In$_{0.3}$Ga$_{0.7}$As/AlAs strained quantum wells. An improved tight-binding model was used to optimize the structure parameters in order to obtain the shortest wavelength intersubband transition ever achieved in a semiconductor system. The corresponding transitions occur between the first confined electronic levels of the well following mid-infrared optical pumping of electrons from the barrier X-valley into the well ground state., Comment: To appear in Applied Physics Letters

Published
2000
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6. Andreev reflection in Si-engineered Al/InGaAs hybrid junctions

Author

De Franceschi, Silvano, Giazotto, Francesco, Beltram, Fabio, Sorba, Lucia, Lazzarino, Marco, and Franciosi, Alfonso

Subjects
Condensed Matter - Superconductivity, Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

Andreev-reflection dominated transport is demonstrated in Al/n-In0.38Ga0.62As superconductor-semiconductor junctions grown by molecular beam epitaxy on GaAs(001). High junction transparency was achieved in low-doped devices by exploiting Si interface bilayers to suppress the native Schottky barrier. It is argued that this technique is ideally suited for the fabrication of ballistic transport hybrid microstructures., Comment: 9 REVTEX pages + 3 postscript figures, to be published in APL 73, (28dec98)

Published
1998
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7. The Elettra 2.0 Beamlines.

Author

Gregoratti, Luca, Lizzit, Silvano, Karantzoulis, Emanuel, and Franciosi, Alfonso

Subjects
SPECKLE interference, SYNCHROTRON radiation, HARD X-rays, ATOMIC force microscopy techniques
Abstract

The Elettra synchrotron radiation facility in Trieste, Italy has been operating since 1994 and is currently the only facility operating at 2.0 or 2.4 GeV. Plans are underway to construct a new facility, Elettra 2.0, which will have improved capabilities and a wider range of experiments. The project was approved in 2017 and is expected to be operational in 2027, offering diverse beamlines for various energy ranges and advanced imaging and spectroscopy techniques. The construction will include 12 new beamlines and upgrades to existing ones. [Extracted from the article]

Published
2024
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8. Introduction

Author

Chelikowsky, James R., Franciosi, Alfonso, Cardona, Manuel, editor, Fulde, Peter, editor, von Klitzing, Klaus, editor, Queisser, Hans-Joachim, editor, Lotsch, Helmut K. V., editor, Chelikowsky, James R., editor, and Franciosi, Alfonso, editor

Published
1991
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10. Ga2Se3 Nanowires via Au-Assisted Heterovalent Exchange Reaction on GaAs

Author

Berto, Federico, primary, Haghighian, Niloofar, additional, Ferfolja, Katja, additional, Gardonio, Sandra, additional, Fanetti, Mattia, additional, Martelli, Faustino, additional, Mussi, Valentina, additional, Dubrovskii, Vladimir G., additional, Shtrom, Igor V., additional, Franciosi, Alfonso, additional, and Rubini, Silvia, additional

Published
2020
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11. Microstructure of ruthenium dioxide films grown on α–Al2O3 (0001), α–Al2O3 (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$1\overline 1 02$$\end{document}), and SrTiO3 (100) using reactive sputtering

Author

Wang, Q., Gilmer, Dave, Fan, Yue, Franciosi, Alfonso, Evans, D. Fennell, Gladfelter, Wayne L., and Zhang, Xiao Feng

Published
1997
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12. Transmission electron microscopy and cathodoluminescence studies of extended defects in electron-beam-pumped Zn(sub 1-x)Cd(sub x)Se/ZnSe blue green lasers

Author

Bonard, Jean-Marc, Ganiere, Jean-Daniel, Vanzetti, Lia, Paggel, Jens J., Sorba, Lucia, Franciosi, Alfonso, Herve, Denis, and Molva, Engin

Subjects
Transmission electron microscopes -- Usage, Cathodoluminescence -- Usage, Electron beams -- Research, Semiconductor lasers -- Research, Diodes, Laser -- Research, Physics
Abstract

Results of studies conducted on extended defects in electron-beam-pumped Zn(sub 1-x)Cd(sub x)Se/ZnSe blue and blue-green laser structures are presented. Thin foil samples were sequentially investigated using transmission electron microscopy (TEM) and cathodoluminescence (CL) microscopy to establish a direct correlation between the local luminescence properties and the presence of structural defects. Nonradiative defects by CL were observed with no extended defect counterparts in TEM.

Published
1998

16. Assessing the Projects on the ESFRI Roadmap

Author

Calvia Goetz, A., Franciosi, Alfonso, Larsen, S., Marks, J., Tichmann, K., Wade, R., Zic Fuchs, M., Calvia Goetz, A., Franciosi, Alfonso, Larsen, S., Marks, J., Tichmann, K., Wade, R., and Zic Fuchs, M.

Subjects
Research Infrastructures
Abstract

The implementation of the European facilities on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) is critical for the EU to remain at the forefront of science and technology and be competitive in a global knowledge-based economy. That is why the EU has set itself the target of implementing at least 60% of the ESFRI roadmap by 2015 through its Innovation Union flagship initiative. This process should be accompanied by sound assessment of the progress that projects have made since they were put on the ESFRI roadmap. A high level expert group conducted an in-depth analysis of all the non-scientific aspects of the projects. The report identifies open issues and bottlenecks that are currently delaying the implementation of the ESFRI roadmap projects and assess whether the facilities are likely to be implemented by 2015. The report also offers detailed recommendations on how to overcome obstacles and difficulties. A lot of work still remains to be done by the projects, the stakeholders, the Member States and the European Commission to ensure that the European infrastructures are operational.

Published
2014

17. Ga2Se3Nanowires via Au-Assisted Heterovalent Exchange Reaction on GaAs

Author

Berto, Federico, Haghighian, Niloofar, Ferfolja, Katja, Gardonio, Sandra, Fanetti, Mattia, Martelli, Faustino, Mussi, Valentina, Dubrovskii, Vladimir G., Shtrom, Igor V., Franciosi, Alfonso, and Rubini, Silvia

Abstract

Out-of-plane Ga2Se3nanowires are grown by molecular beam epitaxy via Au-assisted heterovalent exchange reaction on GaAs substrates in the absence of Ga deposition. It is shown that at a suitable temperature around 560 °C the Au-decorated GaAs substrate releases Ga atoms, which react with the incoming Se and feed the nanowire growth. The nanowire composition, crystal structure, and morphology are characterized by Raman spectroscopy and electron microscopy. The growth mechanism is investigated by X-ray photoelectron spectroscopy. We explore the growth parameter window and find an interesting effect of shortening of the nanowires after a certain maximum length. The nanowire growth is described within a diffusion transport model, which explains the nonmonotonic behavior of the nanowire length versus the growth parameters. Nanowire shortening is explained by the blocking of Ga supply from the GaAs substrate by thick, in-plane worm-like Ga2Se3structures, which grow concomitantly with the nanowires, followed by backward diffusion of Ga atoms from the nanowires down to the substrate surface.

Published
2020
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18. Combined transmission electron microscopy and cathodoluminescence studies of degradation in...

Author

Bonard, Jean-Marc, Ganiere, Jean-Daniel, Vanzetti, Lia, Paggel, Jens J., Sorba, Lucia, Franciosi, Alfonso, Herve, Denis, and Molva, Engin

Subjects
PHYSICS experiments, CATHODOLUMINESCENCE, LASERS
Abstract

Presents information on a study conducted which investigated the combination of cathodoluminescence measurements in a scanning electron microscope with transmission electron microscopy, in the degradation of electron-beam-pumped Zn1-xCdxSe/ZnSe laser structures. Development of a method to explain the formation and propagation of the degradation defects; Development of incoherent and coherent light emitters based on II-VI semiconductors.

Published
1998
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19. Band offsets in Zn1-xCdxSe/ZnSe multiple quantum wells.

Author

Pellegrini, Vittorio, Tredicucci, Alessandro, Beltram, Fabio, Vanzetti, Lia, Lazzarino, Marco, and Franciosi, Alfonso

Subjects
CONDUCTION bands, QUANTUM wells, MOLECULAR beam epitaxy
Abstract

Presents a study that evaluated the conduction-band discontinuity in Zn[sub1-x]Cd[subx]Se/ZnSe multiple-quantum-well structures grown by molecular-beam epitaxy and pseudomorphically strained to ZnSe. Sketch of the conduction-band diagram in the case of predominant tunnel contribution (Low temperature and high applied bias) to the observed current; Thermionic analysis and intesubband absorption; Sample description and experiment.

Published
1996
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21. Silicon interface layers at GaAs/AIGaAs heterojunctions

Author

De Franceschi, Silvano, Altomare, Fabio, Beltram, Fabio, Lazzarino, Marco, Sorba, Lucia, and Franciosi, Alfonso

Subjects
Silicon -- Research, Physics -- Research, Physics
Abstract

The applicability of the Si interface layer (IL) method to band-offset tuning has been explored. Transport measurements were performed as a function of temperature on GaAs/AIGaAs/GaAs test structures. Fabrication of Si ILs is found not to be a suitable option to control the band offset of GaAs/AIGaAs heterojunctions for low growth temperatures below 500 degrees C. Si diffusion and segregation were prominent despite the relatively low growth temperatures used.

Published
1998

24. Interaction between conduction band edge and nitrogen states probed by carrier effective-mass measurements in GaAs(1-x)N(x)

Author

Masia, F, Pettinari, G, Polimeni, A, Felici, M, Miriametro, A, Capizzi, M, Lindsay, A, Healy, S. B., O'Reilly, E. P., Cristofoli, A, Bais, G, Piccin, M, Rubini, S, Martelli, F, Franciosi, Alfonso, Klar, P. J, Volz, K, Stolz, W., Masia, F, Pettinari, G, Polimeni, A, Felici, M, Miriametro, A, Capizzi, M, Lindsay, A, HEALY S., B, O'REILLY E., P, Cristofoli, A, Bais, G, Piccin, M, Rubini, S, Martelli, F, Franciosi, Alfonso, Klar, P. J, Volz, K, and Stolz, W.

Subjects
semiconductors, impuritie, semiconductor, impurities, Nitrides
Abstract

The electron effective mass, me, has been determined by magnetophotoluminescence in as-grown and hydrogenated Ga As1-x Nx samples for a wide range of nitrogen concentrations (from x

Published
2006

25. Influence of N-cluster states on the gyromagnetic factor of electrons in GaAs(1-x)N(x)

Author

PETTINARI G, MASIA F, POLIMENI A, FELICI M, FROVA A, CAPIZZI M, LINDSAY A, O'REILLY E. P, KLAR P. J, STOLZ W, BAIS G, PICCIN M, RUBINI S, MARTELLI F, FRANCIOSI, ALFONSO, Pettinari, G, Masia, F, Polimeni, A, Felici, M, Frova, A, Capizzi, M, Lindsay, A, O'REILLY E., P, KLAR P., J, Stolz, W, Bais, G, Piccin, M, Rubini, S, Martelli, F, and Franciosi, Alfonso

Subjects
nitrides, semiconductors, impurities, impuritie, semiconductor
Abstract

The effective gyromagnetic factor of electrons, ge*, has been determined by Zeeman splitting measurements in a large number of Ga As1-x Nx GaAs (x

Published
2006

26. Site of Mn delta-doped GaAs: x-ray absorption spectroscopy

Author

D'ACAPITO F, SMOLENTSEV G, BOSCHERINI F, PICCIN M, BAIS G, RUBINI S, MARTELLI F, FRANCIOSI, ALFONSO, D'Acapito, F, Smolentsev, G, Boscherini, F, Piccin, M, Bais, G, Rubini, S, Martelli, F, and Franciosi, Alfonso

Published
2006

34. Tunable Schottky Barrier Contacts to In1-xGaxAs

Author

Marinelli, C., Sorba, L., Lazzarino, M., Kumar, D., Pelucchi, E., Mller, B. H., Orani, D., Rubini, S., Franciosi, Alfonso, DE FRANCESCHI, S., Beltram, F., Marinelli, C., Sorba, L., Lazzarino, M., Kumar, D., Pelucchi, E., Mller, B. H., Orani, D., Rubini, S., Franciosi, Alfonso, DE FRANCESCHI, S., and Beltram, F.

Published
2000

37. 1.26 $��$m intersubband transitions in In$_{0.3}$Ga$_{0.7}$As/AlAs quantum wells

Author

C. PASCUAL GARCIA, A. DE NARDIS, V. PELLEGRINI, JANCU J. M., BELTRAM F., MLLER B. H., SORBA L., FRANCIOSI, ALFONSO, C., PASCUAL GARCIA, A., DE NARDIS, V., Pellegrini, Jancu, J. M., Beltram, F., Mller, B. H., Sorba, L., and Franciosi, Alfonso

Subjects
Condensed Matter::Materials Science, Condensed Matter::Other, Materials Science (cond-mat.mtrl-sci), FOS: Physical sciences, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

We observed room-temperature intersubband transitions at 1.26 microns in n-doped type-II In$_{0.3}$Ga$_{0.7}$As/AlAs strained quantum wells. An improved tight-binding model was used to optimize the structure parameters in order to obtain the shortest wavelength intersubband transition ever achieved in a semiconductor system. The corresponding transitions occur between the first confined electronic levels of the well following mid-infrared optical pumping of electrons from the barrier X-valley into the well ground state., To appear in Applied Physics Letters

Published
2000
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40. Zn0.85Cd0.15Se Active Layers on Graded-composition InxGa1-xAs Buffer Layer

Author

Mueller, B. H., Lantier, R., Sorba, L., Heun, S., Rubini, S., Lazzarino, M., Franciosi, Alfonso, Napolitani, E., Romanato, F., Drigo, A., Lazzarini, L., Salviati, G., Mueller, B. H., Lantier, R., Sorba, L., Heun, S., Rubini, S., Lazzarino, M., Franciosi, Alfonso, Napolitani, E., Romanato, F., Drigo, A., Lazzarini, L., and Salviati, G.

Published
1999

43. Formation and dissolution of D-N complexes in dilute nitrides

Author

Berti, Marina, primary, Bisognin, Gabriele, additional, De Salvador, Davide, additional, Napolitani, Enrico, additional, Vangelista, Silvia, additional, Polimeni, Antonio, additional, Capizzi, Mario, additional, Boscherini, Federico, additional, Ciatto, Gianluca, additional, Rubini, Silvia, additional, Martelli, Faustino, additional, and Franciosi, Alfonso, additional

Published
2007
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44. Manganese-Induced Growth of GaAs Nanowires

Author

Martelli, Faustino, primary, Rubini, Silvia, additional, Piccin, Matteo, additional, Bais, Giorgio, additional, Jabeen, Fauzia, additional, De Franceschi, Silvano, additional, Grillo, Vincenzo, additional, Carlino, Elvio, additional, D'Acapito, Francesco, additional, Boscherini, Federico, additional, Cabrini, Stefano, additional, Lazzarino, Marco, additional, Businaro, Luca, additional, Romanato, Filippo, additional, and Franciosi, Alfonso, additional

Published
2006
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45. Semiconductor Heterojunction Engineering

Author

MINNESOTA UNIV MINNEAPOLIS, Franciosi, Alfonso, MINNESOTA UNIV MINNEAPOLIS, and Franciosi, Alfonso

Abstract

Semiconductor interfaces such heterojunctions and metal/semiconductor contacts are crucial components of modern solid state electronic devices ranging from MOSFETs and MODFETs to LEDs and lasers. The possibility of tuning the interface potential barrier to a given device application and optimizing carrier injection or confinement would offer an important new degree of freedom in device design. The focus of our work was the characterization and control of the band alignment in a number of interfaces of current interest for the development of a viable blue optoelectronic technology. These included wide gap II-VI and III-V semiconductor materials fabricated by molecular beam epitaxy (MBE) on GaAs wafers. We have exploited the MBE growth parameter to vary the interface composition and morphology, and examined the resulting variations in the structural and electronic properties of the junctions. Among the major successes of our program was the fabrication of local interface dipoles in the interface region of II-VI/III-V heterojunctions to independently tune band offsets and structural properties, the implementation of metal/ZnSe contacts with unprecedentedly low resistivity, and the development of new substrates lattice-matched to the active layer for the fabrication of II-VI based blue-green lasers.

Published
1997

50. Polaronic excitons inZnxCd1−xSe/ZnSequantum wells

Author

De Nardis, Andrea, primary, Pellegrini, Vittorio, additional, Colombelli, Raffaele, additional, Beltram, Fabio, additional, Vanzetti, Lia, additional, Franciosi, Alfonso, additional, Krivorotov, I. N., additional, and Bajaj, K. K., additional

Published
2000
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