Luca Andena | Politecnico di Milano (original) (raw)

Papers by Luca Andena

Proceedings of the ... International Symposium on Microelectronics, Mar 7, 2024

Advanced Optical Materials, Nov 16, 2022

Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to... more Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to display high carrier concentrations due to their defect-heavy structures, independent of the preparation method. Such high doping enables these materials to display plasmonic resonances, tunable by varying their stoichiometry, as shown previously for Cu2-xS, Cu2-xSe, and Cu2-xTe, with 0<x<1. Here, we study plasmonic dynamics in drop-cast Cu9S5 (digenite) nanocrystals (NCs) film using ultrafast pump-probe spectroscopy. The NCs were synthesized by thermal annealing of copper foil using chemical vapor deposition (CVD), followed by sonication and drop-casting of the isolated few-layered flakes on different substrates. The samples displayed a broad localized surface plasmon resonance (LSPR) in the near-infrared (NIR), peaking at 2100 nm. The free carrier response is further confirmed by fitting the linear absorption with a Drude-Lorentz effective medium approximation model. Investigation of the ultrafast dynamics of free carriers in the film was performed by exciting the material with 50-fs-long pulses centered at 1800 nm and probing both in the NIR (1200-1750 nm) and visible (530-730 nm) spectral ranges. The high temporal resolution allowed us to measure the relaxation dynamics of the photo-excited holes, which are dominated by a fast decay (τ1 = 360 ± 20 fs) and correspond to hole-phonon scattering processes, followed by a long-lived (τ2 > 1 ns) signal associated with phonon-phonon scattering relaxation. These results confirm the possibility of fabricating Cu9S5 films retaining the plasmonic properties of individual NCs, anticipating integrating these films into heterojunctions with suitable hole acceptor materials to build hot-hole-transfer-based optoelectronic devices.

Zenodo (CERN European Organization for Nuclear Research), Oct 17, 2022

Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to... more Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to display high carrier concentrations due to their defect-heavy structures, independent of the preparation method. Such high doping enables these materials to display plasmonic resonances, tunable by varying their stoichiometry, as shown previously for Cu2-xS, Cu2-xSe, and Cu2-xTe, with 0<x<1. Here, we study plasmonic dynamics in drop-cast Cu9S5 (digenite) nanocrystals (NCs) film using ultrafast pump-probe spectroscopy. The NCs were synthesized by thermal annealing of copper foil using chemical vapor deposition (CVD), followed by sonication and drop-casting of the isolated few-layered flakes on different substrates. The samples displayed a broad localized surface plasmon resonance (LSPR) in the near-infrared (NIR), peaking at 2100 nm. The free carrier response is further confirmed by fitting the linear absorption with a Drude-Lorentz effective medium approximation model. Investigation of the ultrafast dynamics of free carriers in the film was performed by exciting the material with 50-fs-long pulses centered at 1800 nm and probing both in the NIR (1200-1750 nm) and visible (530-730 nm) spectral ranges. The high temporal resolution allowed us to measure the relaxation dynamics of the photo-excited holes, which are dominated by a fast decay (τ1 = 360 ± 20 fs) and correspond to hole-phonon scattering processes, followed by a long-lived (τ2 > 1 ns) signal associated with phonon-phonon scattering relaxation. These results confirm the possibility of fabricating Cu9S5 films retaining the plasmonic properties of individual NCs, anticipating integrating these films into heterojunctions with suitable hole acceptor materials to build hot-hole-transfer-based optoelectronic devices.

2023 24th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)

CRC Press eBooks, Nov 28, 2022

In this work, a visco-hyperelastic numerical model is proposed, based on the decoupling of the st... more In this work, a visco-hyperelastic numerical model is proposed, based on the decoupling of the strain and time dependent contributions. Four different rubber blends, used for the production of athletics tracks, have been experimentally characterized in compression under varying loading histories. A robust identification procedure provided reliable constitutive parameters to be implemented in the numerical simulations. Model predictions have been validated against the outcome of impact tests per formed on the different materials using an Artificial Athlete. Results demonstrate that the presence of a viscoelastic component grants a more accurate description of the energy return characteristics of rub bers under dynamic conditions.

CRC Press eBooks, Nov 28, 2022

5th CellMAT 2018 - Cellular Materials, 2018

Journal of Applied Polymer Science

Scratch and mar visibility is measured through a purposely designed black box. The present method... more Scratch and mar visibility is measured through a purposely designed black box. The present method for the quantification of the scratch visibility agrees with human eye evaluation. The color of the material has a crucial effect on the scratch visibility. Experimental procedure to measure the scratch visibility is shown in the graphical abstract: a) the scratched sample is located into the black box setup; b) the images taken in the step "a" are analyzed to quantify the onset of visibility; c) the results are quantitatively compared to the human eye perception of the scratch.

Wear

In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, r... more In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, rubber-toughened polybutylene terephthalate, linear low-density polyethylene) were characterized in terms of their bulk (modulus and yield stress) and surface (scratch hardness) mechanical properties. The intrinsic time-dependence of the materials was addressed by performing DMA and compression tests at varying testing speed/frequency, exploiting timetemperature superposition and Eyring's model to obtain data at strain rates compatible with scratch experiments. The latter were performed by applying different loading histories (constant depth or load) and indenters. Scratch hardness was determined using Pelletier's model; it was demonstrated that such a parameter provides a reliable and almost intrinsic (i.e. loading history independent) evaluation of scratch resistance, seen as the resistance the material opposes to indenter penetration. Its relation with other aspects of the scratch phenomenon (in particular deformation recovery) was also explored, accounting for the specific deformation regime imposed by the indenter (transitioning from elastic to predominantly plastic).

Materials

The fatigue behavior of a filled non-crystallizing elastomer was investigated on axisymmetric dum... more The fatigue behavior of a filled non-crystallizing elastomer was investigated on axisymmetric dumbbell specimens. By plotting relevant Wöhler curves, a power law behavior was found. In addition, temperature increases due to heat build-up were monitored. In order to distinguish between initiation and crack growth regimes, hysteresis curves, secant and dynamic moduli, dissipated and stored energies, and normalized minimum and maximum forces were analyzed. Even though indications related to material damaging were observed, a clear trend to recognize the initiation was not evident. Further details were revealed by considering a fracture mechanics. The analysis of the fracture surfaces evidenced the presence of three regions, associated to initiation, fatigue striation, and catastrophic failure. Additional fatigue tests were performed with samples in which a radial notch was introduced. This resulted in a reduction in lifetime by four orders of magnitude; nevertheless, the fracture surfa...

2° CONVEGNO NAZIONALE ASSOCOMPOSITI, 2012

Composites Part B: Engineering, 2022

Lubricants

Innovative nanostructured materials offer the possibility of enhancing the tribological performan... more Innovative nanostructured materials offer the possibility of enhancing the tribological performance of traditional materials like graphite and molybdenum disulfide (MoS2). In this study, the scratch resistance of two different copper powders, dendritic and spherical, and their composites with traditional MoS2, nanometric MoS2, and graphene nanoplatelets was investigated. Metal powder metallurgy was employed to produce composite materials with 5 wt% and 10 wt% of each solid lubricant. A ball milling step was employed to grind and mix the matrix copper powder with the lubricants. The use of a cold press combined with the sintering in inert atmosphere at 550 °C limited the oxidation of the copper and the degradation of the solid lubricants. The so-produced materials were characterized through a variety of techniques such as micro-indentation hardness, electrical resistivity, contact angle wettability, X-ray diffraction, Raman scattering, and scanning electron microscopy. Moreover, micr...

Pavement and Asset Management

Peridynamics (Silling, "Reformulation of elasticity theory for discontinuities and long-ran... more Peridynamics (Silling, "Reformulation of elasticity theory for discontinuities and long-range forces." J. Mech. Phys. Solids, 2000 (48): 175-209) is a recently developed non-local continuum theory for solid materials that is particularly suited to handle discontinuities in the displacement field, such as those arising during fracture phenomena. Peridynamics prescribes that each material point interacts with all the neighbours contained in a sphere of given radius, called the horizon; this assumption introduces a characteristic length scale in the continuum description. In a nutshell, the interactions between material points depend on their relative distance; in the peridynamics framework, which heavily borrows concepts from molecular dynamics, this distance is called the “bond length”. The equations of motion holding at each material point, rather than linking the accelerations with the divergence of the stress tensor, link the material point acceleration to the integra...

Proceedings of the ... International Symposium on Microelectronics, Mar 7, 2024

Advanced Optical Materials, Nov 16, 2022

Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to... more Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to display high carrier concentrations due to their defect-heavy structures, independent of the preparation method. Such high doping enables these materials to display plasmonic resonances, tunable by varying their stoichiometry, as shown previously for Cu2-xS, Cu2-xSe, and Cu2-xTe, with 0<x<1. Here, we study plasmonic dynamics in drop-cast Cu9S5 (digenite) nanocrystals (NCs) film using ultrafast pump-probe spectroscopy. The NCs were synthesized by thermal annealing of copper foil using chemical vapor deposition (CVD), followed by sonication and drop-casting of the isolated few-layered flakes on different substrates. The samples displayed a broad localized surface plasmon resonance (LSPR) in the near-infrared (NIR), peaking at 2100 nm. The free carrier response is further confirmed by fitting the linear absorption with a Drude-Lorentz effective medium approximation model. Investigation of the ultrafast dynamics of free carriers in the film was performed by exciting the material with 50-fs-long pulses centered at 1800 nm and probing both in the NIR (1200-1750 nm) and visible (530-730 nm) spectral ranges. The high temporal resolution allowed us to measure the relaxation dynamics of the photo-excited holes, which are dominated by a fast decay (τ1 = 360 ± 20 fs) and correspond to hole-phonon scattering processes, followed by a long-lived (τ2 > 1 ns) signal associated with phonon-phonon scattering relaxation. These results confirm the possibility of fabricating Cu9S5 films retaining the plasmonic properties of individual NCs, anticipating integrating these films into heterojunctions with suitable hole acceptor materials to build hot-hole-transfer-based optoelectronic devices.

Zenodo (CERN European Organization for Nuclear Research), Oct 17, 2022

Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to... more Copper chalcogenides are materials characterized by intrinsic doping properties, allowing them to display high carrier concentrations due to their defect-heavy structures, independent of the preparation method. Such high doping enables these materials to display plasmonic resonances, tunable by varying their stoichiometry, as shown previously for Cu2-xS, Cu2-xSe, and Cu2-xTe, with 0<x<1. Here, we study plasmonic dynamics in drop-cast Cu9S5 (digenite) nanocrystals (NCs) film using ultrafast pump-probe spectroscopy. The NCs were synthesized by thermal annealing of copper foil using chemical vapor deposition (CVD), followed by sonication and drop-casting of the isolated few-layered flakes on different substrates. The samples displayed a broad localized surface plasmon resonance (LSPR) in the near-infrared (NIR), peaking at 2100 nm. The free carrier response is further confirmed by fitting the linear absorption with a Drude-Lorentz effective medium approximation model. Investigation of the ultrafast dynamics of free carriers in the film was performed by exciting the material with 50-fs-long pulses centered at 1800 nm and probing both in the NIR (1200-1750 nm) and visible (530-730 nm) spectral ranges. The high temporal resolution allowed us to measure the relaxation dynamics of the photo-excited holes, which are dominated by a fast decay (τ1 = 360 ± 20 fs) and correspond to hole-phonon scattering processes, followed by a long-lived (τ2 > 1 ns) signal associated with phonon-phonon scattering relaxation. These results confirm the possibility of fabricating Cu9S5 films retaining the plasmonic properties of individual NCs, anticipating integrating these films into heterojunctions with suitable hole acceptor materials to build hot-hole-transfer-based optoelectronic devices.

2023 24th International Conference on Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)

CRC Press eBooks, Nov 28, 2022

In this work, a visco-hyperelastic numerical model is proposed, based on the decoupling of the st... more In this work, a visco-hyperelastic numerical model is proposed, based on the decoupling of the strain and time dependent contributions. Four different rubber blends, used for the production of athletics tracks, have been experimentally characterized in compression under varying loading histories. A robust identification procedure provided reliable constitutive parameters to be implemented in the numerical simulations. Model predictions have been validated against the outcome of impact tests per formed on the different materials using an Artificial Athlete. Results demonstrate that the presence of a viscoelastic component grants a more accurate description of the energy return characteristics of rub bers under dynamic conditions.

CRC Press eBooks, Nov 28, 2022

5th CellMAT 2018 - Cellular Materials, 2018

Journal of Applied Polymer Science

Scratch and mar visibility is measured through a purposely designed black box. The present method... more Scratch and mar visibility is measured through a purposely designed black box. The present method for the quantification of the scratch visibility agrees with human eye evaluation. The color of the material has a crucial effect on the scratch visibility. Experimental procedure to measure the scratch visibility is shown in the graphical abstract: a) the scratched sample is located into the black box setup; b) the images taken in the step "a" are analyzed to quantify the onset of visibility; c) the results are quantitatively compared to the human eye perception of the scratch.

Wear

In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, r... more In this work four different polymers (acrylonitrile-butadiene-styrene, high-impact polystyrene, rubber-toughened polybutylene terephthalate, linear low-density polyethylene) were characterized in terms of their bulk (modulus and yield stress) and surface (scratch hardness) mechanical properties. The intrinsic time-dependence of the materials was addressed by performing DMA and compression tests at varying testing speed/frequency, exploiting timetemperature superposition and Eyring's model to obtain data at strain rates compatible with scratch experiments. The latter were performed by applying different loading histories (constant depth or load) and indenters. Scratch hardness was determined using Pelletier's model; it was demonstrated that such a parameter provides a reliable and almost intrinsic (i.e. loading history independent) evaluation of scratch resistance, seen as the resistance the material opposes to indenter penetration. Its relation with other aspects of the scratch phenomenon (in particular deformation recovery) was also explored, accounting for the specific deformation regime imposed by the indenter (transitioning from elastic to predominantly plastic).

Materials

The fatigue behavior of a filled non-crystallizing elastomer was investigated on axisymmetric dum... more The fatigue behavior of a filled non-crystallizing elastomer was investigated on axisymmetric dumbbell specimens. By plotting relevant Wöhler curves, a power law behavior was found. In addition, temperature increases due to heat build-up were monitored. In order to distinguish between initiation and crack growth regimes, hysteresis curves, secant and dynamic moduli, dissipated and stored energies, and normalized minimum and maximum forces were analyzed. Even though indications related to material damaging were observed, a clear trend to recognize the initiation was not evident. Further details were revealed by considering a fracture mechanics. The analysis of the fracture surfaces evidenced the presence of three regions, associated to initiation, fatigue striation, and catastrophic failure. Additional fatigue tests were performed with samples in which a radial notch was introduced. This resulted in a reduction in lifetime by four orders of magnitude; nevertheless, the fracture surfa...

2° CONVEGNO NAZIONALE ASSOCOMPOSITI, 2012

Composites Part B: Engineering, 2022

Lubricants

Innovative nanostructured materials offer the possibility of enhancing the tribological performan... more Innovative nanostructured materials offer the possibility of enhancing the tribological performance of traditional materials like graphite and molybdenum disulfide (MoS2). In this study, the scratch resistance of two different copper powders, dendritic and spherical, and their composites with traditional MoS2, nanometric MoS2, and graphene nanoplatelets was investigated. Metal powder metallurgy was employed to produce composite materials with 5 wt% and 10 wt% of each solid lubricant. A ball milling step was employed to grind and mix the matrix copper powder with the lubricants. The use of a cold press combined with the sintering in inert atmosphere at 550 °C limited the oxidation of the copper and the degradation of the solid lubricants. The so-produced materials were characterized through a variety of techniques such as micro-indentation hardness, electrical resistivity, contact angle wettability, X-ray diffraction, Raman scattering, and scanning electron microscopy. Moreover, micr...

Pavement and Asset Management

Peridynamics (Silling, "Reformulation of elasticity theory for discontinuities and long-ran... more Peridynamics (Silling, "Reformulation of elasticity theory for discontinuities and long-range forces." J. Mech. Phys. Solids, 2000 (48): 175-209) is a recently developed non-local continuum theory for solid materials that is particularly suited to handle discontinuities in the displacement field, such as those arising during fracture phenomena. Peridynamics prescribes that each material point interacts with all the neighbours contained in a sphere of given radius, called the horizon; this assumption introduces a characteristic length scale in the continuum description. In a nutshell, the interactions between material points depend on their relative distance; in the peridynamics framework, which heavily borrows concepts from molecular dynamics, this distance is called the “bond length”. The equations of motion holding at each material point, rather than linking the accelerations with the divergence of the stress tensor, link the material point acceleration to the integra...