A5066334907- Semiconductor Quantum Structures and Devices
- Photonic and Optical Devices
- Semiconductor materials and devices
- Spectroscopy and Laser Applications
- Advancements in Semiconductor Devices and Circuit Design
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Silicon Nanostructures and Photoluminescence
- Semiconductor materials and interfaces
- Graphene research and applications
- Semiconductor Lasers and Optical Devices
- Nanowire Synthesis and Applications
- Electronic and Structural Properties of Oxides
- Terahertz technology and applications
- Thin-Film Transistor Technologies
- Electron and X-Ray Spectroscopy Techniques
- Optical Coatings and Gratings
- Silicon and Solar Cell Technologies
- Strong Light-Matter Interactions
- Atmospheric Ozone and Climate
- Superconducting and THz Device Technology
- Force Microscopy Techniques and Applications
- Advanced Semiconductor Detectors and Materials
- Physics of Superconductivity and Magnetism
- Diamond and Carbon-based Materials Research
Roma Tre University
2016-2025
University of Glasgow
2019-2021
Sapienza University of Rome
1995-2021
University of Pisa
2021
ETH Zurich
2019
Istituto Nazionale per la Fisica della Materia
1996-2000
University of Rome Tor Vergata
1999
Istituto Nazionale di Fisica Nucleare, Sezione di Roma I
1996-1998
Fondazione "Ugo Bordoni"
1991
Due to the ever growing use of optical fibers in communications, for both long distances and local area networks, there is an increasing effort toward realization high speed efficiency detectors, operating low-absorption regions (1.3-1.55µm) silica fibers. Although III-V semiconductors provide detection range interest, incorporating them well-established Si-based very large scale integration technology difficult expensive[ 1 ]. Ge-on-Si structures represents a viable alternative solution...
Exploiting Ge K-edge x-ray absorption spectroscopy we provide direct evidence of Si–Ge intermixing in self-organized strained and unstrained quantum dots on Si, a quantitative measurement the average composition. For Ge/Si(001) with equivalent thickness range 5.8–38 nm morphology ranging from that typical coherently to associated relaxed find Si composition is approximately 30%. Ge/Si(111), wetting layer has near 50%. We discuss these results terms energetics dot formation argue...
Germanium is emerging as the substrate of choice for growth graphene in CMOS-compatible processes. For future application next generation devices accurate control over properties high-quality synthesized on Ge surfaces, such number layers and domain size, paramount importance. Here we investigate role process gas flows CVD Ge(100). The quality morphology deposited material assessed by using μ-Raman spectroscopy, X-ray photoemission scanning electron microscopy, atomic force microscopy. We...
Abstract We use low-temperature scanning tunnelling 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, VB < 0, apparent shape can be described as round protrusion surrounded by moat-like depression (sombrero). As voltage increases, changes, eventually evolving into depression. From images, determine adsorption site hollow position....
We present a new experimental method for determining band lineups at the semiconductor heterojunctions and apply it to $c\ensuremath{-}\mathrm{S}\mathrm{i}\left(100\right)/a\ensuremath{-}\mathrm{S}\mathrm{i}:\mathrm{H}$ heterostructure. This uses modern version of an old spectroscopy: photoelectric yield spectroscopy excited with photons in near UV range. It is shown that both substrate overlayer valence-band tops can be identified spectrum due high escape depth dynamical range technique,...
In this letter, we present an atomic-force-microscopy investigation of the Stranski–Krastanov growth Ge on Si(100). Upon increasing base width islands, two morphology transitions are found. The first transition occurs at a ∼50–60 nm and marks evolution from few-monolayer-thick terraces to square-base pyramidal islands. second transition, which takes place when exceeds ∼300 nm, island shape changes square pyramids tetragonal truncated pyramids. Both brought about by need for system minimize...
We develop a generalized theory for the scattering process produced by interface roughness on charge carriers and which is suitable any semiconductor heterostructure. By exploiting our experimental insights into three-dimensional atomic landscape obtained Ge/GeSi heterointerfaces atom probe tomography, we have been able to define full set of parameters relevant potential, including both in-plane axial correlation inside real diffuse interfaces. Our findings indicate partial coherence along...
The threading dislocation density (TDD) in plastically relaxed Ge/Si(001) heteroepitaxial films is commonly observed to decrease progressively with their thickness due mutual annihilation. However, there exists a saturation limit, known as the geometrical beyond which further of TDD Ge film hindered. Here, we show that such limit can be overcome SiGe/Ge/Si heterostructures thanks beneficial role second interface. Indeed, ${\mathrm{Si}}_{0.06}{\mathrm{Ge}}_{0.94}/\mathrm{Ge}/\mathrm{Si}(001)$...
Thick Ge/(Si,Ge) multiple-quantum-well heterostructures are interesting for silicon-integrated optoelectronic devices operating in the midinfrared and terahertz spectral regions. The epitaxy of such structures becomes increasingly challenging as their thickness increases, due to accumulation strain defects. This study proves that ultrahigh-vacuum chemical vapor deposition allows subnanometer control compositional profile throughout micrometer-thick strain-compensated multilayered with very...
Highly efficient and transparent multicomponent catalysts for Dye Solar Cells (DSCs) were obtained by simultaneous electrodeposition of platinum cobalt-sulfide (Pt:CoS) on conducting glass substrates from a mixture solution both precursors. At equal charge transfer resistances (RCT), the superior transparency electrodeposited (ED) Pt:CoS compared to ED Pt-only CoS-only was attributed synergic combination very thin CoS layer fine dispersion Pt nanoparticles. The highly catalytic properties...
Quantum cascade lasers are finicky, in terms of the structural quality active region, especially for strain-mismatched heterostructures like Ge/Si-Ge quantum wells. Accurate control electron-state coupling between well and barriers laser's different stages is crucial. This study shows how to produce high-quality asymmetric coupled $n$-type multiple wells carefully resonant tunneling through thicknesses, thus interwell wave-function hybridization. The set robust material parameters provided...
n-type Ge/SiGe terahertz quantum cascade lasers are investigated using non-equilibrium Green's functions calculations. We compare the temperature dependence of gain properties with an equivalent GaAs/AlGaAs laser design. In case, is found to be much more robust increase, enabling operation up room temperature. The better robustness respect III–V attributed weaker interaction optical phonons. effect lower interface quality and can partly overcome by engineering smoother confinement.
In this letter we present an atomic force microscopy and photoluminescence investigation of two- three-dimensional Ge structures deposited on Si(100) substrates. The spectra demonstrated the presence quantum confinement effects in flat uncapped layers islands even for relatively large size structures. Moreover, a correlation between sample morphology features is demonstrated.
We analyze the linewidth of intersubband absorption features observed in $n$-type $s\text{\ensuremath{-}}\mathrm{Ge}/{\mathrm{Ge}}_{0.82}{\mathrm{Si}}_{0.18}$ multiquantum wells grown on Si(001) substrates. Supported by a thorough theoretical modeling, we discuss role line broadening electron scattering due to interface roughness, spatial distribution and density ionized donors, phonons, alloy disorder, extended defects. To this aim, spectra set samples featuring different well widths doping...
Interfaces play an essential role in the performance of ever-shrinking semiconductor devices, making comprehensive determination their three-dimensional (3D) structural properties increasingly important. This becomes even more relevant compositional interfaces, as is case for Ge/GeSi heterostructures, where chemical intermixing pronounced addition to morphology. We use electron tomography method reconstruct buried interfaces and layers asymmetric coupled Ge/Ge0.8Si0.2 multiquantum wells,...
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 fascinating optics applications leveraging on this property, we use technologically relevant SiGe material system design, grow, and characterize n-type doped realized continuously grading Ge-rich Si
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 giant order nonlinear susceptibility. A characteristic the chosen material system is existence large off-diagonal elements
We have investigated the weak antilocalization effect in a high-density two-dimensional electron gas (2DEG) an AlGaN/GaN heterostructure. The data were analyzed using most representative theories on (WAL) correction to magnetoconductivity. spin-orbit interaction (SOI) strength and phase-coherence time extracted from fitting experimental data. found that use of WAL peak analysis appears be reliable way investigating SOI dependence charge concentration revealed by as reported literature can...
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 Si substrate by ultrahigh vacuum chemical vapor deposition, have been investigated. The design is based single well active region employing vertical optical transition the observed spectral features are described non-equilibrium...