The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Giovanni Isella - One of the best experts on this subject based on the ideXlab platform.
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Doping dependence of the electron spin diffusion length in Germanium
APL Materials, 2019Co-Authors: Carlo Zucchetti, Monica Bollani, Giovanni Isella, Maurizio Zani, Marco Finazzi, Federico BottegoniAbstract:We have investigated the electron spin diffusion length at room temperature in bulk n-Doped Germanium as a function of the doping concentration. To this purpose, we exploit a nonlocal spin injection/detection scheme where spins are optically injected at the direct gap of Ge and electrically detected by means of the inverse spin-Hall effect (ISHE). By optically generating a spin population in the conduction band of the semiconductor at different distances from the spin detector, we are able to directly determine the electron spin diffusion length Ls in the Ge substrate. We experimentally observe that Ls > 20 μm for lightly Doped samples and, by taking into account the electron diffusion coefficient, we estimate electron spin lifetime values τs larger than 50 ns. In contrast, for heavily Doped Ge substrates, the spin diffusion length decreases to a few micrometers, corresponding to τs ≈ 20 ns. These results can be exploited to refine spin transport models in Germanium and reduce the experimental uncertainties associated with the evaluation of Ls from other spin injection/detection techniques.We have investigated the electron spin diffusion length at room temperature in bulk n-Doped Germanium as a function of the doping concentration. To this purpose, we exploit a nonlocal spin injection/detection scheme where spins are optically injected at the direct gap of Ge and electrically detected by means of the inverse spin-Hall effect (ISHE). By optically generating a spin population in the conduction band of the semiconductor at different distances from the spin detector, we are able to directly determine the electron spin diffusion length Ls in the Ge substrate. We experimentally observe that Ls > 20 μm for lightly Doped samples and, by taking into account the electron diffusion coefficient, we estimate electron spin lifetime values τs larger than 50 ns. In contrast, for heavily Doped Ge substrates, the spin diffusion length decreases to a few micrometers, corresponding to τs ≈ 20 ns. These results can be exploited to refine spin transport models in Germanium and reduce the experimental uncertainti...
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imaging spin diffusion in Germanium at room temperature
Physical Review B, 2017Co-Authors: Carlo Zucchetti, Giovanni Isella, Federico Bottegoni, C Vergnaud, Franco Ciccacci, Lavinia Ghirardini, Michele Celebrano, Fabian Rortais, Alberto Ferrari, A MartyAbstract:We report on the nonlocal detection of optically oriented spins in lightly $n$-Doped Germanium at room temperature. Localized spin generation is achieved by scanning a circularly polarized laser beam ($\ensuremath{\lambda}=1550$ nm) on an array of lithographically defined Pt microstructures. The in-plane oriented spin generated at the edges of such microstructures, placed at different distances from a spin-detection element, allows for a direct imaging of spin diffusion in the semiconductor, leading to a measured spin diffusion length of about $10\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}$. Two different spin-detection blocks are employed, consisting of either a magnetic tunnel junction or a platinum stripe where the spin current is converted in an electrical signal by the inverse spin-Hall effect. The second solution represents the realization of a nonlocal spin-injection/detection scheme that is completely free from ferromagnetic functional blocks.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, Costanza Manganelli, Michele VirgilioAbstract:Heavily Doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μm wavelength range at least. In this work, we investigate the electrodynamics of heavily n-type-Doped Germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and Germanium substrates, are in situ Doped with phosphorous in the 10 17 to 10 19 cm−3 range, then screened plasma frequencies in the 100 to 1200 cm−1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of Germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n-type-Doped Germanium at room temperature.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, C L Manganelli, Michele VirgilioAbstract:Mid-infrared plasmonics has the potential to revolutionize molecular sensing technology, if integrated into optoelectronic chips. Recently,several groups working on plasmonics have substituted metals with heavily Doped semiconductors for the sake of integration, also opening up the possibility of tuning the device response via the doping level. In this work, the authors analyze the relevant case of heavily Doped Ge films by combining transport measurements with infrared spectroscopy. They demonstrate a broad tunability of the screened plasma frequency up to the mid-infrared range. The main loss channels are identified through comparison of the experimental scattering rates with quantum calculations and pump-probe measurements. Heavily Doped Ge is highlighted as a viable route for the integration of mid-infrared plasmonics into silicon optoelectronic platforms.
Michele Virgilio - One of the best experts on this subject based on the ideXlab platform.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, Costanza Manganelli, Michele VirgilioAbstract:Heavily Doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μm wavelength range at least. In this work, we investigate the electrodynamics of heavily n-type-Doped Germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and Germanium substrates, are in situ Doped with phosphorous in the 10 17 to 10 19 cm−3 range, then screened plasma frequencies in the 100 to 1200 cm−1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of Germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n-type-Doped Germanium at room temperature.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, C L Manganelli, Michele VirgilioAbstract:Mid-infrared plasmonics has the potential to revolutionize molecular sensing technology, if integrated into optoelectronic chips. Recently,several groups working on plasmonics have substituted metals with heavily Doped semiconductors for the sake of integration, also opening up the possibility of tuning the device response via the doping level. In this work, the authors analyze the relevant case of heavily Doped Ge films by combining transport measurements with infrared spectroscopy. They demonstrate a broad tunability of the screened plasma frequency up to the mid-infrared range. The main loss channels are identified through comparison of the experimental scattering rates with quantum calculations and pump-probe measurements. Heavily Doped Ge is highlighted as a viable route for the integration of mid-infrared plasmonics into silicon optoelectronic platforms.
Monica Bollani - One of the best experts on this subject based on the ideXlab platform.
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Doping dependence of the electron spin diffusion length in Germanium
APL Materials, 2019Co-Authors: Carlo Zucchetti, Monica Bollani, Giovanni Isella, Maurizio Zani, Marco Finazzi, Federico BottegoniAbstract:We have investigated the electron spin diffusion length at room temperature in bulk n-Doped Germanium as a function of the doping concentration. To this purpose, we exploit a nonlocal spin injection/detection scheme where spins are optically injected at the direct gap of Ge and electrically detected by means of the inverse spin-Hall effect (ISHE). By optically generating a spin population in the conduction band of the semiconductor at different distances from the spin detector, we are able to directly determine the electron spin diffusion length Ls in the Ge substrate. We experimentally observe that Ls > 20 μm for lightly Doped samples and, by taking into account the electron diffusion coefficient, we estimate electron spin lifetime values τs larger than 50 ns. In contrast, for heavily Doped Ge substrates, the spin diffusion length decreases to a few micrometers, corresponding to τs ≈ 20 ns. These results can be exploited to refine spin transport models in Germanium and reduce the experimental uncertainties associated with the evaluation of Ls from other spin injection/detection techniques.We have investigated the electron spin diffusion length at room temperature in bulk n-Doped Germanium as a function of the doping concentration. To this purpose, we exploit a nonlocal spin injection/detection scheme where spins are optically injected at the direct gap of Ge and electrically detected by means of the inverse spin-Hall effect (ISHE). By optically generating a spin population in the conduction band of the semiconductor at different distances from the spin detector, we are able to directly determine the electron spin diffusion length Ls in the Ge substrate. We experimentally observe that Ls > 20 μm for lightly Doped samples and, by taking into account the electron diffusion coefficient, we estimate electron spin lifetime values τs larger than 50 ns. In contrast, for heavily Doped Ge substrates, the spin diffusion length decreases to a few micrometers, corresponding to τs ≈ 20 ns. These results can be exploited to refine spin transport models in Germanium and reduce the experimental uncertainti...
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, Costanza Manganelli, Michele VirgilioAbstract:Heavily Doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μm wavelength range at least. In this work, we investigate the electrodynamics of heavily n-type-Doped Germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and Germanium substrates, are in situ Doped with phosphorous in the 10 17 to 10 19 cm−3 range, then screened plasma frequencies in the 100 to 1200 cm−1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of Germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n-type-Doped Germanium at room temperature.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, C L Manganelli, Michele VirgilioAbstract:Mid-infrared plasmonics has the potential to revolutionize molecular sensing technology, if integrated into optoelectronic chips. Recently,several groups working on plasmonics have substituted metals with heavily Doped semiconductors for the sake of integration, also opening up the possibility of tuning the device response via the doping level. In this work, the authors analyze the relevant case of heavily Doped Ge films by combining transport measurements with infrared spectroscopy. They demonstrate a broad tunability of the screened plasma frequency up to the mid-infrared range. The main loss channels are identified through comparison of the experimental scattering rates with quantum calculations and pump-probe measurements. Heavily Doped Ge is highlighted as a viable route for the integration of mid-infrared plasmonics into silicon optoelectronic platforms.
Ferreira A Da Silva - One of the best experts on this subject based on the ideXlab platform.
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heavily n Doped ge low temperature magnetoresistance properties on the metallic side of the metal nonmetal transition
Journal of Applied Physics, 2020Co-Authors: Ferreira A Da Silva, M Toloza A Sandoval, A Levine, E Levinson, H Boudinov, Bo E SerneliusAbstract:We report here an experimental and theoretical study on the magnetoresistance properties of heavily phosphorous Doped Germanium on the metallic side of the metal–nonmetal transition. An anomalous regime, formed by negative values of the magnetoresistance, was observed by performing low-temperature measurements and explained within the generalized Drude model, due to the many-body effects. It reveals a key mechanism behind the magnetoresistance properties at low temperatures and, therefore, constitutes a path to its manipulation in such materials of great interest in fundamental physics and technological applications.We report here an experimental and theoretical study on the magnetoresistance properties of heavily phosphorous Doped Germanium on the metallic side of the metal–nonmetal transition. An anomalous regime, formed by negative values of the magnetoresistance, was observed by performing low-temperature measurements and explained within the generalized Drude model, due to the many-body effects. It reveals a key mechanism behind the magnetoresistance properties at low temperatures and, therefore, constitutes a path to its manipulation in such materials of great interest in fundamental physics and technological applications.
Jacopo Frigerio - One of the best experts on this subject based on the ideXlab platform.
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optical properties of highly n Doped Germanium obtained by in situ doping and laser annealing
Journal of Physics D, 2017Co-Authors: Jacopo Frigerio, Andrea Ballabio, Valeria Giliberti, L Baldassarre, Kevin Gallacher, Ross W Millar, Ruggero Milazzo, Luca Maiolo, A Minotti, Federico BottegoniAbstract:High n-type doping in Germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in Germanium. An activated n-doping concentration of 8.8 × 1019 cm−3 has been achieved starting from an incorporated phosphorous concentration of 1.1 × 1020 cm−3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, Costanza Manganelli, Michele VirgilioAbstract:Heavily Doped semiconductor thin films are very promising for application in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in the 5 to 50 μm wavelength range at least. In this work, we investigate the electrodynamics of heavily n-type-Doped Germanium epilayers at infrared frequencies beyond the assumptions of the Drude model. The films are grown on silicon and Germanium substrates, are in situ Doped with phosphorous in the 10 17 to 10 19 cm−3 range, then screened plasma frequencies in the 100 to 1200 cm−1 range were observed. We employ infrared spectroscopy, pump-probe spectroscopy, and dc transport measurements to determine the tunability of the plasma frequency. Although no plasmonic structures have been realized in this work, we derive estimates of the decay time of mid-infrared plasmons and of their figures of merit for field confinement and for surface plasmon propagation. The average electron scattering rate increases almost linearly with excitation frequency, in agreement with quantum calculations based on a model of the ellipsoidal Fermi surface at the conduction band minimum of Germanium accounting for electron scattering with optical phonons and charged impurities. Instead, we found weak dependence of plasmon losses on neutral impurity density. In films where a transient plasma was generated by optical pumping, we found significant dependence of the energy relaxation times in the few-picosecond range on the static doping level of the film, confirming the key but indirect role played by charged impurities in energy relaxation. Our results indicate that underdamped mid-infrared plasma oscillations are attained in n-type-Doped Germanium at room temperature.
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tunability of the dielectric function of heavily Doped Germanium thin films for mid infrared plasmonics
Physical Review B, 2016Co-Authors: Jacopo Frigerio, Monica Bollani, Giovanni Isella, Andrea Ballabio, Emilie Sakat, Giovanni Pellegrini, Paolo Biagioni, E Napolitani, C L Manganelli, Michele VirgilioAbstract:Mid-infrared plasmonics has the potential to revolutionize molecular sensing technology, if integrated into optoelectronic chips. Recently,several groups working on plasmonics have substituted metals with heavily Doped semiconductors for the sake of integration, also opening up the possibility of tuning the device response via the doping level. In this work, the authors analyze the relevant case of heavily Doped Ge films by combining transport measurements with infrared spectroscopy. They demonstrate a broad tunability of the screened plasma frequency up to the mid-infrared range. The main loss channels are identified through comparison of the experimental scattering rates with quantum calculations and pump-probe measurements. Heavily Doped Ge is highlighted as a viable route for the integration of mid-infrared plasmonics into silicon optoelectronic platforms.