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1. How orbitals and oxidation states determine apparent topographies in scanning tunneling microscopy: the case of fluorine on silver surfaces

Author

Pueyo, Adrián Gómez, Sánchez, Jazmín Aragón, Degtev, Ilya, Temperini, Maria Eleonora, Jezierski, Daniel, Hogan, Conor, Caporale, Antonio, Di Gaspare, Luciana, Persichetti, Luca, De Seta, Monica, Grochala, Wojciech, Barone, Paolo, Camilli, Luca, and Lorenzana, José

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

We use density functional theory calculations to characterize the early stages of fluorination of silver's (100) and (110) surfaces. In the Ag(100) surface, the hollow site is the most favorable for F adatoms. In the Ag(110) surface, three adsorption sites, namely hollow, long bridge, and short bridge, exhibit similar energies. These locations are also more favorable than an F adatom occupying a vacancy site irrespectively of whether the vacancy was present or not in the pristine surface. The computed energy as a function of surface coverage is used to compute the equilibrium thermodynamics phase diagram. We argue that for the typical pressure and temperature of fluorination experiments, the state of the surface is not determined by thermodynamics but by kinetics. Combining these results with scanning tunneling microscopy (STM) topographic simulations, we propose assignments to features observed experimentally. We present a minimal model of the apparent topography of adatoms in different locations in terms of hydrogenic orbitals, explaining the observed trends. The model links the STM apparent topography to structural information and the oxidation states of the Ag atoms near the adatom., Comment: 18 pages, 12 Figures

Published
2024

2. The initial stages of silver fluorination: a scanning tunneling microscopy investigation

Author

Sánchez, Jazmín Aragón, Caporale, Antonio, Degtev, Ilya, Di Gaspare, Luciana, Persichetti, Luca, Sansotera, Maurizio, Pueyo, Adrián Gómez, De Seta, Monica, Lorenzana, José, and Camilli, Luca

Subjects
Condensed Matter - Materials Science
Abstract

We use low-temperature scanning tunneling microscopy (LT-STM) to characterize the early stages of silver fluorination. On Ag(100), we observe only one adsorbate species, which shows a bias-dependent STM topography. Notably, at negative bias voltages, $V_{\rm B}<0$, the apparent shape can be described as a round protrusion surrounded by a moat-like depression (sombrero). As the voltage increases, the apparent shape changes, eventually evolving into a round depression. From the STM images, we determine the adsorption site to be the hollow position. On Ag(110) we find adsorbates with three distinct STM topographies. One type exhibits the same shape change with $V_{\rm B}$ as observed on Ag(100), that is, from a sombrero shape to a round depression as the voltage changes from negative to positive values; the other two types are observed as round depressions regardless of $V_{\rm B}$. From the STM images, we find the three adsorbates to be sitting on the short-bridge, hollow and top position on the Ag(110) surface, with a relative abundance of 60\%, 35\% and 5\%., Comment: 13 pages, 7 figures

Published
2024

3. Asymmetric-coupled Ge/SiGe quantum wells for second harmonic generation at 7.1 THz in integrated waveguides: a theoretical study

Author

Talamas Simola Enrico, Ortolani Michele, Di Gaspare Luciana, Capellini Giovanni, De Seta Monica, and Virgilio Michele

Subjects
second harmonic generation, terahertz, ge/sige quantum wells, non linear waveguide, silicon photonics, Physics, QC1-999
Abstract

We present a theoretical investigation of guided second harmonic generation at THz frequencies in SiGe waveguides embedding n-type Ge/SiGe asymmetric coupled quantum wells to engineer a giant second order nonlinear susceptibility. A characteristic of the chosen material system is the existence of large off-diagonal elements in the χ 2 tensor, coupling optical modes with different polarization. To account for this effect, we generalize the coupled-mode theory, proposing a theoretical model suitable for concurrently resolving every second harmonic generation interaction among guide-sustained modes, regardless of which χ 2 tensor elements it originates from. Furthermore, we exploit the presence of off-diagonal χ 2 elements and the peculiarity of the SiGe material system to develop a simple and novel approach to achieve perfect phase matching without requiring any fabrication process. For a realistic design of the quantum heterostructure we estimate second order nonlinear susceptibility peak values of ∼7 and ∼1.4 × 105 pm/V for diagonal and off diagonal χ 2 elements, respectively. Embedding such heterostructure in Ge-rich SiGe waveguides of thicknesses of the order of 10–15 μm leads to second harmonic generation efficiencies comprised between 0.2 and 2 %, depending on the choice of device parameters. As a case study, we focus on the technologically relevant frequency of 7.1 THz, yet the results we report may be extended to the whole 5–20 THz range.

Published
2024
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4. High-quality CMOS compatible n-type SiGe parabolic quantum wells for intersubband photonics at 2.5–5 THz

Author

Campagna Elena, Talamas Simola Enrico, Venanzi Tommaso, Berkmann Fritz, Corley-Wiciak Cedric, Nicotra Giuseppe, Baldassarre Leonetta, Capellini Giovanni, Di Gaspare Luciana, Virgilio Michele, Ortolani Michele, and De Seta Monica

Subjects
heterostructures, germanium, terahertz, strong coupling, parabolic potential, Physics, QC1-999
Abstract

A parabolic potential that confines charge carriers along the growth direction of quantum wells semiconductor systems is characterized by a single resonance frequency, associated to intersubband transitions. Motivated by fascinating quantum optics applications leveraging on this property, we use the technologically relevant SiGe material system to design, grow, and characterize n-type doped parabolic quantum wells realized by continuously grading Ge-rich Si1−x Gex alloys, deposited on silicon wafers. An extensive structural analysis highlights the capability of the ultra-high-vacuum chemical vapor deposition technique here used to precisely control the quadratic confining potential and the target doping profile. The absorption spectrum, measured by means of Fourier transform infrared spectroscopy, revealed a single peak with a full width at half maximum at low and room temperature of about 2 and 5 meV, respectively, associated to degenerate intersubband transitions. The energy of the absorption resonance scales with the inverse of the well width, covering the 2.5–5 THz spectral range, and is almost independent of temperature and doping, as predicted for a parabolic confining potential. On the basis of these results, we discuss the perspective observation of THz strong light–matter coupling in this silicon compatible material system, leveraging on intersubband transitions embedded in all-semiconductor microcavities.

Published
2024
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5. THz intersubband electroluminescence from n-type Ge/SiGe quantum cascade structures

Author

Stark, David, Mirza, Muhammad, Persichetti, Luca, Montanari, Michele, Markmann, Sergej, Beck, Mattias, Grange, Thomas, Birner, Stefan, Virgilio, Michele, Ciano, Chiara, Ortolani, Michele, Corley, Cedric, Capellini, Giovanni, Di Gaspare, Luciana, De Seta, Monica, Paul, Douglas J., Faist, Jérôme, and Scalari, Giacomo

Subjects
Physics - Optics, Physics - Applied Physics
Abstract

We report electroluminescence originating from L-valley transitions in n-type Ge/Si$_{0.15}$Ge$_{0.85}$ quantum cascade structures centered at 3.4 and 4.9 THz with a line broadening of $\Delta f/f \approx 0.2$. Three strain-compensated heterostructures, grown on a Si substrate by ultrahigh vacuum chemical vapor deposition, have been investigated. The design is based on a single quantum well active region employing a vertical optical transition and the observed spectral features are well described by non-equilibrium Green's function calculations. The presence of two peaks highlights a suboptimal injection in the upper state of the radiative transition. Comparison of the electroluminescence spectra with similar GaAs/AlGaAs structure yields one order of magnitude lower emission efficiency.

Published
2021
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6. Tuning the doping of epitaxial graphene on a conventional semiconductor via substrate surface reconstruction

Author

Galbiati, Miriam, Persichetti, Luca, Gori, Paola, Pulci, Olivia, Bianchi, Marco, Di Gaspare, Luciana, Tersoff, Jerry, Coletti, Camilla, Hofmann, Philip, De Seta, Monica, and Camilli, Luca

Subjects
Condensed Matter - Materials Science
Abstract

Combining scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we demonstrate how to tune the doping of epitaxial graphene from p to n by exploiting the structural changes that occur spontaneously on the Ge surface upon thermal annealing. Furthermore, using first principle calculations we build a model that successfully reproduces the experimental observations. Since the ability to modify graphene electronic properties is of fundamental importance when it comes to applications, our results provide an important contribution towards the integration of graphene with conventional semiconductors.

Published
2020
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7. Intersubband transition engineering in the conduction band of asymmetric coupled Ge/SiGe quantum wells

Author

Persichetti, Luca, Montanari, Michele, Ciano, Chiara, Di Gaspare, Luciana, Ortolani, Michele, Baldassarre, Leonetta, Zoellner, Marvin H., Mukherjee, Samik, Moutanabbir, Oussama, Capellini, Giovanni, Virgilio, Michele, and De Seta, Monica

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

: n-type Ge/SiGe asymmetric-coupled quantum wells represent the building block of a variety of nanoscale quantum devices, including recently proposed designs for a silicon-based THz quantum cascade laser. In this paper, we combine structural and spectroscopic experiments on 20-module superstructures, each featuring two Ge wells coupled through a Ge-rich tunnel barrier, as a function of the geometry parameters of the design and the P dopant concentration. Through the comparison of THz spectroscopic data with numerical calculations of intersubband optical absorption resonances, we demonstrated that it is possible to tune by design the energy and the spatial overlap of quantum confined subbands in the conduction band of the heterostructures. The high structural/interface quality of the samples and the control achieved on subband hybridization are the promising starting point towards a working electrically pumped light-emitting device.

Published
2020
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11. Electronic and morphological properties of the graphene/Ge(110) interface as a function of temperature

Author

Caporale, Antonio, Persichetti, Luca, Galbiati, Miriam, Di Gaspare, Luciana, Pis, Igor, Bondino, Federica, Veigang-Radulescu, V.-P., Babenko, V., Hofmann, S., Gori, P., Pulci, O., Bianchi, M., Hofmann, P., Tersoff, J., De Seta, M., Gunnella, R., and Camilli, Luca

Abstract

accepted for oral presentation to ECOSS36 (https://www.ecoss36.uni.lodz.pl/) &nbsp

Published
2023
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12. Subnanometer Control of the Heteroepitaxial Growth of Multimicrometer-Thick Ge /( Si , Ge ) Quantum Cascade Structures

Author

Talamas Simola, Enrico, primary, Montanari, Michele, additional, Corley-Wiciak, Cedric, additional, Di Gaspare, Luciana, additional, Persichetti, Luca, additional, Zöllner, Marvin H., additional, Schubert, Markus A., additional, Venanzi, Tommaso, additional, Trouche, Marina Cagnon, additional, Ortolani, Michele, additional, Mattioli, Francesco, additional, Sfuncia, Gianfranco, additional, Nicotra, Giuseppe, additional, Capellini, Giovanni, additional, Virgilio, Michele, additional, and De Seta, Monica, additional

Published
2023
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13. THz silicon photonics: an intersubband emitter

Author

Stark, David, primary, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Markmann, Sergej, additional, Beck, Mattias, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, Ciano, Chiara, additional, Ortolani, Michele, additional, Corley-Wiciak, Cedric, additional, Capellini, Giovanni, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Paul, Douglas J., additional, Faist, Jérôme, additional, and Scalari, Giacomo, additional

Published
2022
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14. THz electroluminescence from n-type Ge/SiGe quantum cascade structures

Author

Scalari, Giacomo, primary, Stark, David, additional, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, Ciano, Chiara, additional, Ortolani, Michele, additional, Corley, Cedric, additional, Capellini, Giovanni, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Paul, Douglas J., additional, and Faist, Jerome, additional

Published
2022
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15. Tracking Interfacial Changes of Graphene/Ge(110) During In-Vacuum Annealing

Author

Camilli, Luca, primary, Galbiati, Miriam, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Píš, Igor, additional, Bondino, Federica, additional, Caporale, Antonio, additional, Veigang-Radulescu, Vlad-Petru, additional, Hofmann, Stephan, additional, Sodo, Armida, additional, Gunnella, Roberto, additional, and Persichetti, Luca, additional

Published
2022
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16. THz Intersubband Emitter based on Silicon

Author

Stark, David, primary, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Markmann, Sergej, additional, Beck, Mattias, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, Ciano, Chiara, additional, Ortolani, Michele, additional, Corley, Cedric, additional, Capellini, Giovanni, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Paul, Douglas J., additional, Faist, Jerome, additional, and Scalari, Giacomo, additional

Published
2021
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17. Terahertz intersubband electroluminescence from n-type germanium quantum wells

Author

Stark, David, primary, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Markmann, Sergej, additional, Beck, Mattias, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, Ciano, Chiara, additional, Ortolani, Michele, additional, Corley, Cedric, additional, Capellini, Giovanni, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Paul, Douglas J., additional, Faist, Jerome, additional, and Scalari, Giacomo, additional

Published
2021
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18. Controlling the relaxation mechanism of low strain Si1−xGex/Si(001) layers and reducing the threading dislocation density by providing a preexisting dislocation source

Author

Becker, Lucas, Storck, Peter, Schulz, Tobias, Zoellner, Marvin H., Di Gaspare, Luciana, Rovaris, Fabrizio, Marzegalli, Anna, Montalenti, Francesco, Capellini, Giovanni, Schwalb, Georg, Schroeder, Thomas, and Albrecht, Martin

Subjects
Silicon, Germanium, Dislocations, Epitaxy
Abstract

Strain relaxedSi1−𝑥Ge𝑥 buffer layers on Si(001) can be used as virtual substrates for the growth of both strained Si and strained SiGe, which are suitable materials for sub-7 nm CMOS devices due to their enhanced carrier mobility. For industrial applications, the threading dislocation density (TDD) has to be as low as possible. However, a reduction of the TDD is limited by the balance between dislocation glide and nucleation as well as dislocation blocking. The relaxation mechanism of low strainSi0.98Ge0.02 layers on commercial substrates is compared to substrates with a predeposited SiGe backside layer, which provides threading dislocations at the edge of the wafer. It is shown that by the exploitation of this reservoir, the critical thickness for plastic relaxation is reduced and the formation of misfit dislocation bundles can be prevented. Instead, upon reaching the critical thickness, these preexisting dislocations simultaneously glide unhindered from the edge of the wafer toward the center. The resulting dislocation network is free of thick dislocation bundles that cause pileups, and the TDD can be reduced by one order of magnitude.

Published
2020

19. Design and simulation of losses in Ge/SiGe terahertz quantum cascade laser waveguides

Author

Gallacher, Kevin, Ortolani, Michele, Ciano, Chiara, Baldassarre, Leonetta, Virgilio, Michele, Scalari, Giacomo, Faist, Jérôme, Di Gaspare, Luciana, De Seta, Monica, Capellini, Giovanni, Grange, Thomas, Birner, Stefan, and Paul, Douglas J.

Abstract

The waveguide losses from a range of surface plasmon and double metal waveguides for Ge/Si1−xGex THz quantum cascade laser gain media are investigated at 4.79 THz (62.6 μm wavelength). Double metal waveguides demonstrate lower losses than surface plasmonic guiding with minimum losses for a 10 μm thick active gain region with silver metal of 21 cm−1 at 300 K reducing to 14.5 cm−1 at 10 K. Losses for silicon foundry compatible metals including Al and Cu are also provided for comparison and to provide a guide for gain requirements to enable lasers to be fabricated in commercial silicon foundries. To allow these losses to be calculated for a range of designs, the complex refractive index of a range of nominally undoped Si1−xGex with x = 0.7, 0.8 and 0.9 and doped Ge heterolayers were extracted from Fourier transform infrared spectroscopy measurements between 0.1 and 10 THz and from 300 K down to 10 K. The results demonstrate losses comparable to similar designs of GaAs/AlGaAs quantum cascade laser plasmon waveguides indicating that a gain threshold of 15.1 cm−1 and 23.8 cm−1 are required to produce a 4.79 THz Ge/SiGe THz laser at 10 K and 300 K, respectively, for 2 mm long double metal waveguide quantum cascade lasers with facet coatings., Optics Express, 28 (4), ISSN:1094-4087

Published
2020

20. Tuning the Doping of Epitaxial Graphene on a Conventional Semiconductor via Substrate Surface Reconstruction

Author

Galbiati, Miriam, Persichetti, Luca, Gori, Paola, Pulci, Olivia, Bianchi, Marco, Di Gaspare, Luciana, Tersoff, Jerry, Coletti, Camilla, Hofmann, Philip, De Seta, Monica, Camilli, Luca, Galbiati, Miriam, Persichetti, Luca, Gori, Paola, Pulci, Olivia, Bianchi, Marco, Di Gaspare, Luciana, Tersoff, Jerry, Coletti, Camilla, Hofmann, Philip, De Seta, Monica, and Camilli, Luca

Abstract

Combining scanning tunneling microscopy and angle-resolved photoemission spectroscopy, we demonstrate how to tune the doping of epitaxial graphene from p to n by exploiting the structural changes that occur spontaneously on the Ge surface upon thermal annealing. Furthermore, using first-principle calculations, we build a model that successfully reproduces the experimental observations. Since the ability to modify graphene electronic properties is of fundamental importance when it comes to applications, our results provide an important contribution toward the integration of graphene with conventional semiconductors.

Published
2021

21. THz intersubband absorption in n-type Si1−xGex parabolic quantum wells

Author

Montanari, Michele, primary, Ciano, Chiara, additional, Persichetti, Luca, additional, Corley, Cedric, additional, Baldassarre, Leonetta, additional, Ortolani, Michele, additional, Di Gaspare, Luciana, additional, Capellini, Giovanni, additional, Stark, David, additional, Scalari, Giacomo, additional, Virgilio, Michele, additional, and De Seta, Monica, additional

Published
2021
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22. THz intersubband electroluminescence from n-type Ge/SiGe quantum cascade structures

Author

Stark, David, primary, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Markmann, Sergej, additional, Beck, Mattias, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, Ciano, Chiara, additional, Ortolani, Michele, additional, Corley, Cedric, additional, Capellini, Giovanni, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Paul, Douglas J., additional, Faist, Jérôme, additional, and Scalari, Giacomo, additional

Published
2021
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23. THz emission from n-type Ge/SiGe quantum cascade structures

Author

Stark, David, primary, Mirza, Muhammad, additional, Persichetti, Luca, additional, Montanari, Michele, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Virgilio, Michele, additional, Ortolani, Michele, additional, Capellini, Giovanni, additional, Grange, Thomas, additional, Birner, Stefan, additional, Paul, Douglas J., additional, Faist, Jérôme, additional, and Scalari, Giacomo, additional

Published
2021
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26. N-Type Ge/SiGe Multi-Quantum Wells for THz Light Emission: High Quality Growth and Material Parameter Calibration

Author

Persichetti, Luca, primary, Ciano, Chiara, additional, Montanari, Michele, additional, Baldassarre, Leonetta, additional, Di Gaspare, Luciana, additional, Pashkin, Alexej, additional, Helm, Manfred, additional, Skibitzki, Oliver, additional, Zöllner, Marvin, additional, Capellini, Giovanni, additional, Ortolani, Michele, additional, Virgilio, Michele, additional, and De Seta, Monica, additional

Published
2020
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27. Reduction of threading dislocation density beyond the saturation limit by optimized reverse grading

Author

Skibitzki, Oliver, primary, Zoellner, Marvin H., additional, Rovaris, Fabrizio, additional, Schubert, Markus Andreas, additional, Yamamoto, Yuji, additional, Persichetti, Luca, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Gatti, Riccardo, additional, Montalenti, Francesco, additional, and Capellini, Giovanni, additional

Published
2020
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29. Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

Author

Persichetti, Luca, primary, Montanari, Michele, additional, Ciano, Chiara, additional, Di Gaspare, Luciana, additional, Ortolani, Michele, additional, Baldassarre, Leonetta, additional, Zoellner, Marvin, additional, Mukherjee, Samik, additional, Moutanabbir, Oussama, additional, Capellini, Giovanni, additional, Virgilio, Michele, additional, and De Seta, Monica, additional

Published
2020
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30. Terahertz absorption-saturation and emission from electron-doped germanium quantum wells

Author

Ciano, Chiara, primary, Virgilio, Michele, additional, Bagolini, Luigi, additional, Baldassarre, Leonetta, additional, Pashkin, Alexej, additional, Helm, Manfred, additional, Montanari, Michele, additional, Persichetti, Luca, additional, Di Gaspare, Luciana, additional, Capellini, Giovanni, additional, Paul, Douglas J., additional, Scalari, Giacomo, additional, Faist, Jèrome, additional, De Seta, Monica, additional, and Ortolani, Michele, additional

Published
2020
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31. Control of Electron State Coupling in Asymmetric Ge/GeSi Quantum Wells

Author

Ciano, Chiara, Virgilio, Michele, Montanari, Michele, Persichetti, Luca, Di Gaspare, Luciana, Ortolani, Michele, Baldassarre, Leonetta, Zoellner, Marvin H., Skibitzki, Oliver, Scalari, Giacomo, Faist, Jerome, Paul, Douglas J., Scuderi, Mario, Nicotra, Giuseppe, Grange, Thomas, Birner, Stefan, Capellini, Giovanni, and De Seta, Monica

Subjects
Condensed Matter::Mesoscopic Systems and Quantum Hall Effect
Abstract

Theoretical predictions indicate that the n-type Ge/SiGe multi quantum-well system is the most promising material for the realization of a Si-compatible THz quantum cascade laser operating at room temperature. To advance in this direction, we study both experimentally and theoretically asymmetric coupled multi quantum-well samples based on this material system, that can be considered as the basic building block of a cascade architecture. Extensive structural characterization shows the high material quality of strain-symmetrized structures grown by chemical vapor deposition, down to the ultrathin barrier limit. Moreover, THz absorption spectroscopy measurements supported by theoretical modeling unambiguously demonstrate inter-well coupling and wavefunction tunneling. The agreement between experimental data and simulations allowed us to characterize the tunneling barrier parameters and, in turn, achieve a highly-controlled engineering of the electronic structure in forthcoming unipolar cascade systems based on n-type Ge/SiGe multi quantum-wells.

Published
2018
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32. Electron Population Dynamics in Optically Pumped Asymmetric Coupled Ge/SiGe Quantum Wells: Experiment and Models

Author

Ciano, Chiara, primary, Virgilio, Michele, additional, Bagolini, Luigi, additional, Baldassarre, Leonetta, additional, Rossetti, Andrea, additional, Pashkin, Alexej, additional, Helm, Manfred, additional, Montanari, Michele, additional, Persichetti, Luca, additional, Di Gaspare, Luciana, additional, Capellini, Giovanni, additional, Paul, Douglas J., additional, Scalari, Giacomo, additional, Faist, Jèrome, additional, De Seta, Monica, additional, and Ortolani, Michele, additional

Published
2019
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33. n-type Ge/SiGe Multi Quantum-Wells for a THz Quantum Cascade Laser

Author

Ciano, Chiara, primary, Di Gaspare, Luciana, additional, Montanari, Michele, additional, Persichetti, Luca, additional, Baldassarre, Leonetta, additional, Ortolani, Michele, additional, Capellini, Giovanni, additional, Skibitzki, Oliver, additional, Zöllner, Marvin, additional, Faist, Jerome, additional, Scalari, Giacomo, additional, Stark, David, additional, Paul, Douglas J, additional, Rew, Kirsty, additional, Moutanabbir, Oussama, additional, Mukherjee, Samik, additional, Grange, Thomas, additional, Birner, Stefan, additional, Virgilio, Michele, additional, and De Seta, Monica, additional

Published
2019
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35. Electron state coupling in asymmetric Ge/SiGe quantum wells (Conference Presentation)

Author

Persichetti, Luca, primary, Ciano, Chiara, additional, Virgilio, Michele, additional, Montanari, Michele, additional, Di Gaspare, Luciana, additional, Ortolani, Michele, additional, Baldassarre, Leonetta, additional, Zoellner, Marvin, additional, Skibitzki, Oliver, additional, Stark, David, additional, Scalari, Giacomo, additional, Faist, Jérôme, additional, Rew, Kirsty, additional, Paul, Douglas J., additional, Mukherjee, Samik, additional, Moutanabbir, Oussama, additional, Scuderi, Mario, additional, Nicotra, Giuseppe, additional, Grange, Thomas, additional, Birner, Stefan, additional, Capellini, Giovanni, additional, and De Seta, Monica, additional

Published
2019
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37. Dynamics of crosshatch patterns in heteroepitaxy

Author

Rovaris, Fabrizio, primary, Zoellner, Marvin H., additional, Zaumseil, Peter, additional, Marzegalli, Anna, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Schroeder, Thomas, additional, Storck, Peter, additional, Schwalb, Georg, additional, Capellini, Giovanni, additional, and Montalenti, Francesco, additional

Published
2019
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38. Room temperature operation of n-type Ge/SiGe terahertz quantum cascade lasers predicted by non-equilibrium Green's functions

Author

Grange, Thomas, primary, Stark, David, additional, Scalari, Giacomo, additional, Faist, Jérôme, additional, Persichetti, Luca, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Ortolani, Michele, additional, Paul, Douglas J., additional, Capellini, Giovanni, additional, Birner, Stefan, additional, and Virgilio, Michele, additional

Published
2019
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39. Dynamics of crosshatch patterns in heteroepitaxy

Author

Rovaris, F, Zoellner, M, Zaumseil, P, Marzegalli, A, Di Gaspare, L, De Seta, M, Schroeder, T, Storck, P, Schwalb, G, Capellini, G, Montalenti, F, Rovaris, Fabrizio, Zoellner, Marvin H., Zaumseil, Peter, Marzegalli, Anna, Di Gaspare, Luciana, De Seta, Monica, Schroeder, Thomas, Storck, Peter, Schwalb, Georg, Capellini, Giovanni, Montalenti, Francesco, Rovaris, F, Zoellner, M, Zaumseil, P, Marzegalli, A, Di Gaspare, L, De Seta, M, Schroeder, T, Storck, P, Schwalb, G, Capellini, G, Montalenti, F, Rovaris, Fabrizio, Zoellner, Marvin H., Zaumseil, Peter, Marzegalli, Anna, Di Gaspare, Luciana, De Seta, Monica, Schroeder, Thomas, Storck, Peter, Schwalb, Georg, Capellini, Giovanni, and Montalenti, Francesco

Abstract

Regular surface undulations, called cross-hatch patterns, appearing at the free surface of lattice-mismatched heteroepitaxial films are a key signature of plastic relaxation. Here we show that the dynamics of cross-hatch formation is accurately described by a continuum model based on strain-mediated surface diffusion, provided that a realistic distribution of dislocations is considered. We demonstrate quantitative agreement between our time-dependent simulations and dedicated atomic force microscopy experiments on Si0.92Ge0.08 films grown on Si(001) at various thicknesses, finally shedding light on the origin and on the dynamical behavior of a widely investigated pattern, first observed more than half a century ago.

Published
2019

40. Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back

Author

Rovaris, Fabrizio, primary, Zoellner, Marvin H., additional, Zaumseil, Peter, additional, Schubert, Markus A., additional, Marzegalli, Anna, additional, Di Gaspare, Luciana, additional, De Seta, Monica, additional, Schroeder, Thomas, additional, Storck, Peter, additional, Schwalb, Georg, additional, Richter, Carsten, additional, Schülli, Tobias U., additional, Capellini, Giovanni, additional, and Montalenti, Francesco, additional

Published
2018
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41. Photoluminescence from GeSn nano-heterostructures

Author

Schlykow, Viktoria, primary, Zaumseil, Peter, additional, Schubert, Markus Andreas, additional, Skibitzki, Oliver, additional, Yamamoto, Yuji, additional, Klesse, Wolfgang Matthias, additional, Hou, Yaonan, additional, Virgilio, Michele, additional, De Seta, Monica, additional, Di Gaspare, Luciana, additional, Schroeder, Thomas, additional, and Capellini, Giovanni, additional

Published
2018
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42. Misfit-Dislocation Distributions in Heteroepitaxy: From Mesoscale Measurements to Individual Defects and Back

Author

Rovaris, F, Zoellner, M, Zaumseil, P, Schubert, M, Marzegalli, A, Di Gaspare, L, De Seta, M, Schroeder, T, Storck, P, Schwalb, G, Richter, C, Schülli, T, Capellini, G, Montalenti, F, Rovaris, Fabrizio, Zoellner, Marvin H., Zaumseil, Peter, Schubert, Markus A., Marzegalli, Anna, Di Gaspare, Luciana, De Seta, Monica, Schroeder, Thomas, Storck, Peter, Schwalb, Georg, Richter, Carsten, Schülli, Tobias U., Capellini, Giovanni, Montalenti, Francesco, Rovaris, F, Zoellner, M, Zaumseil, P, Schubert, M, Marzegalli, A, Di Gaspare, L, De Seta, M, Schroeder, T, Storck, P, Schwalb, G, Richter, C, Schülli, T, Capellini, G, Montalenti, F, Rovaris, Fabrizio, Zoellner, Marvin H., Zaumseil, Peter, Schubert, Markus A., Marzegalli, Anna, Di Gaspare, Luciana, De Seta, Monica, Schroeder, Thomas, Storck, Peter, Schwalb, Georg, Richter, Carsten, Schülli, Tobias U., Capellini, Giovanni, and Montalenti, Francesco

Abstract

We provide an in-depth characterization of the dislocation distribution in partially relaxed Si0.92Ge0.08/Si(001) films. This is achieved by an innovative and general method, combining two state-of-the-art characterization techniques through suitable modeling. After having inferred the dislocation positions from transmission-electron-microscopy images, we theoretically reproduce scanning-x-ray-diffraction-microscopy tilt maps measured on the very same region of the sample. We obtain a nearly perfect match between model predictions and experimental data. As a result, we claim that it is possible to establish a local, direct correlation between the dislocations revealed by the transmission-electron-microscopy analysis and the measured lattice tilt distribution.

Published
2018

43. Epi-cleaning of Ge/GeSn heterostructures

Author

DI GASPARE, LUCIANA, Sabbagh D, De Seta M, SODO, ARMIDA, Wirths S, Buca D, Zaumseil P, 3, Schroeder T, CAPELLINI, GIOVANNI, DI GASPARE, Luciana, Sabbagh, D, De Seta, M, Sodo, Armida, Wirths, S, Buca, D, Zaumseil, P, Schroeder, T, and Capellini, Giovanni

Subjects
X-ray spectroscopy, Materials science, Hydrogen, Photoemission spectroscopy, Cleaning, Analytical chemistry, General Physics and Astronomy, chemistry.chemical_element, Germanium, Tungsten, Electron spectroscopy, Condensed Matter::Materials Science, chemistry, X-ray photoelectron spectroscopy, Germanium Tin, Physics::Atomic Physics, Spectroscopy, Epitaxy
Abstract

We demonstrate a very-low temperature cleaning technique based on atomic hydrogen irradiation for highly (1 %) tensile strained Ge epilayers grown on metastable, partially strain relaxed GeSn buffer layers. Atomic hydrogen is obtained by catalytic cracking of hydrogen gas on a hot tungsten filament in an ultra-high vacuum chamber. X-ray photoemission spectroscopy, reflection high energy electron spectroscopy, atomic force microscopy, secondary ion mass spectroscopy, and micro-Raman showed that an O- and C-free Ge surface was achieved, while maintaining the same roughness and strain condition of the as-deposited sample and without any Sn segregation, at a process temperature in the 100-300 °C range.

Published
2015

47. Low field magnetotransport in strained Si/SiGe cavities RID C-7045-2008

Author

Scappucci G, DI GASPARE, LUCIANA, Evangelisti F, Giovine E, Notargiacomo A, Leoni R, Piazza V, Pingue P, Beltram F., Scappucci, G, DI GASPARE, Luciana, Evangelisti, F, Giovine, E, Notargiacomo, A, Leoni, R, Piazza, V, Pingue, P, and Beltram, F.

Subjects
Condensed Matter::Materials Science, Condensed Matter::Strongly Correlated Electrons, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Computer Science::Other
Abstract

Low field magnetotransport revealing signatures of ballistic transport effects in strained Si/SiGe cavities is investigated. We fabricated strained Si/SiGe cavities by confining a high mobility Si/SiGe two-dimensional electron gas in a bended nanowire geometry defined by electron-beam lithography and reactive ion etching. The main features observed in the low temperature magnetoresistance curves are the presence of a zero-field magnetoresistance peak and of an oscillatory structure at low fields. By adopting a simple geometrical model we explain the oscillatory structure in terms of electron magnetic focusing. A detailed examination of the zero-field peak line shape clearly shows deviations from the predictions of ballistic weak localization theory.

Published
2005

48. Doped silicon and NIS junctions for bolometer applications RID F-6186-2010

Author

Leoni R, Buonomo B, Castellano G, Mattioli F, Torrioli G, Evangelisti F., DI GASPARE, LUCIANA, Leoni, R, Buonomo, B, Castellano, G, Mattioli, F, Torrioli, G, DI GASPARE, Luciana, and Evangelisti, F.

Subjects
Condensed Matter::Superconductivity, Condensed Matter::Strongly Correlated Electrons
Abstract

We discuss the performance, of a normal metal hot electron bolometer (NHEB) that we have measured at 0.3 K. We found that the noise equivalent power was limited by the amplifier noise. To improve the NHEB power response and to make it more robust and reliable we propose to substitute the normal metal with heavily doped silicon. The heavily doped silicon behaves like a metal with lower carrier concentration and has a smaller electron-phonon thermal coupling. We have fabricated superconductor-doped silicon-superconductor contacts (S-Sm-S) and we have used them as thermometers and coolers. (C) 2003 Elsevier B.V. All rights reserved.

Published
2004

50. A single electron transistor based on Si/SiGe wires

Author

A. NOTARGIACOMO, G. SCAPPUCCI, G. MARIOTTINI, F. EVANGELISTI, E. GIOVINE AND R. LEONI, DI GASPARE, LUCIANA, A., Notargiacomo, DI GASPARE, Luciana, G., Scappucci, G., Mariottini, F., Evangelisti, and E. GIOVINE AND R., Leoni

Published
2003

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