A5068021631- Magnetic and transport properties of perovskites and related materials
- Electronic and Structural Properties of Oxides
- Advanced Condensed Matter Physics
- Photocathodes and Microchannel Plates
- Physics of Superconductivity and Magnetism
- Electron and X-Ray Spectroscopy Techniques
- Machine Learning in Materials Science
- Advancements in Solid Oxide Fuel Cells
- Radiation Therapy and Dosimetry
- Ferroelectric and Piezoelectric Materials
- Semiconductor materials and devices
- Radiation Detection and Scintillator Technologies
- Multiferroics and related materials
- Gas Sensing Nanomaterials and Sensors
- Rare-earth and actinide compounds
- Quantum and electron transport phenomena
- Advanced Chemical Physics Studies
- Topological Materials and Phenomena
- Gyrotron and Vacuum Electronics Research
- Advancements in Battery Materials
- Atomic and Subatomic Physics Research
- Magnetic Properties of Alloys
- Dark Matter and Cosmic Phenomena
- Surface and Thin Film Phenomena
- Electrical and Thermal Properties of Materials
University of Salerno
2016-2025
Cornell University
2018-2023
University of Chicago
2022
Brookhaven National Laboratory
2022
Superconducting and other Innovative Materials and Devices Institute
2010-2019
Centre National de la Recherche Scientifique
2012-2014
École Nationale Supérieure d'Ingénieurs de Caen
2014
GREYC
2011-2014
National Research Council
2012
The properties of photoemission electron sources determine the ultimate performance a wide class accelerators and photon detectors. To date, all high-efficiency visible-light photocathode materials are either polycrystalline or exhibit intrinsic surface disorder, both which limit emitted beam brightness. In this Letter, we demonstrate synthesis epitaxial thin films Cs_{3}Sb on 3C-SiC (001) using molecular-beam epitaxy. Films as 4 nm have quantum efficiencies exceeding 2% at 532 nm. We also...
We report on epitaxial growth of Bi2Se3 topological insulator thin films by Pulsed Laser Deposition (PLD). X-ray diffraction investigation confirms that with a single (001)-orientation can be obtained several substrates in narrow (i.e., 20 °C) range deposition temperatures and at high pressure 0.1 mbar). However, only grown (001)-Al2O3 show an almost-unique in-plane orientation. In-situ spin-resolved angular resolved photoemission spectroscopy experiments, performed the NFFA-APE facility...
Abstract Quantum fluctuations in low-dimensional systems and near quantum phase transitions have significant influences on material properties. Yet, it is difficult to experimentally gauge the strength importance of fluctuations. Here we provide a resonant inelastic x-ray scattering study magnon excitations Mott insulating cuprates. From thin film SrCuO 2 , single- bi-magnon dispersions are derived. Using an effective Heisenberg Hamiltonian generated from Hubbard model, show that...
Spinel-type lithium manganese oxide (LiMn2O4) is considered one of the most promising cathode materials for rechargeable batteries due to its high operating voltage, reduced toxicity, and lower cost compared cobalt-based cathodes. However, stability LiMn2O4 a significant challenge, as it tends degrade over time, with ion segregation leading reduction in battery capacity.
Alkali antimonides are well established as high efficiency, low intrinsic emittance photocathodes for accelerators and photon detectors. However, conventionally grown alkali antimonide films polycrystalline with surface disorder roughness that can limit achievable beam brightness. Ordering the crystalline structure of has potential to deliver higher brightness electron beams by reducing enabling engineering material properties at level atomic layers. In this report, we demonstrate growth...
Understanding the intricate electrochemical processes in solid oxide fuel cell (SOFC) components, especially air electrodes, is crucial for enhancing device performance and durability. In this work, following recent results showing important improvements of SOFCs with room-temperature sputtered gadolinium-doped ceria (GDC) barrier layers, we investigate by standard Distribution Relaxation Time (DRT) analysis influence GDC thickness uniformity on cathodic reaction kinetics. The outcomes...
The magnetic and electronic modifications induced at the interfaces in ${({\text{SrMnO}}_{3})}_{n}/{({\text{LaMnO}}_{3})}_{2n}$ superlattices have been investigated by linear circular dichroism $\text{Mn}\text{ }{L}_{2,3}$ x-ray absorption spectra. Together with theoretical calculations, our data demonstrate that charge redistribution across favors in-plane ferromagnetic (FM) order ${e}_{g}({x}^{2}\ensuremath{-}{y}^{2})$ orbital occupation, agreement average strain. Far from interfaces,...
We report on the role of oxygen content alone structural and transport properties La0.65Sr0.35MnO3−δ (LSMO) thin films. Identical films were deposited side-by-side during a single deposition run subsequently post-annealed separately in vacuum to systematically vary content. All remained coherently strained SrTiO3 substrate, with no broadening rocking curve widths after post-anneal. As decreases, LSMO unit cell expands while metal-insulator transition temperature TMI decreases. A linear...
We use resonant inelastic x-ray scattering to probe the propagation of plasmons in electron-doped cuprate superconductor Sr_{0.9}La_{0.1}CuO_{2}. detect a plasmon gap ∼120 meV at two-dimensional Brillouin zone center, indicating that low-energy Sr_{0.9}La_{0.1}CuO_{2} are not strictly acoustic. The dispersion, including gap, is accurately captured by layered t-J-V model calculations. A similar analysis performed on recent data from other cuprates suggests generic and its size related...
We report the design and performance of a time-resolved electron diffraction apparatus capable producing intense bunches with simultaneously single digit micrometer probe size, long coherence length, 200 fs rms time resolution. measure 5d (peak) beam brightness at sample location in micro-diffraction mode to be 7×1013 A/m2 rad2 . To generate high bunches, system employs efficiency, low emittance semiconductor photocathodes driven wavelength near photoemission threshold repetition rate up 250...
The low-temperature $(<60\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ transport properties of as-grown ${\mathrm{La}}_{0.7}{\mathrm{Sr}}_{0.3}\mathrm{Mn}{\mathrm{O}}_{3}$ ultrathin films, deposited by the molecular beam epitaxy, have been investigated as a function sample thickness (from $40\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}3.5\phantom{\rule{0.3em}{0ex}}\mathrm{nm}$) and in presence an external magnetic field. With decreasing thickness, clear resistivity minimum...
Double-exchange (DE) mechanisms in $R{E}_{1\ensuremath{-}x}A{E}_{x}{\text{MnO}}_{3}$ manganites (where $RE$ is a trivalent rare-earth ion and $AE$ divalent alkali-earth ion) relies on the strong exchange interaction between two ${\text{Mn}}^{3+}$ ${\text{Mn}}^{4+}$ ions through interfiling oxygen $2p$ states. Nevertheless, role of has ever been considered ``silent'' with respect to DE conducting mechanisms. Here we show that new path for mechanism indeed possible by partially replacing...
Electric noise measurements can give useful information on the conduction mechanisms and dynamic behaviors of charge carriers in new materials. However, it is well known that not all electronic fluctuations are originated from material itself, but some sources depend experimental procedures used for measurements. In this article, an technique to reduce “external” components, associated with bulk system, presented. The proposed method based voltage spectral density, using sequence a four-...
We report on transport properties of oxide manganite La0.7Ba0.3MnO3−δ (LBMO) thin films deposited by pulsed laser deposition (PLD) technique. Detailed analysis heavy-ion stoichiometric composition has been carried out as a function laser-pulse fluence and ambient oxygen pressure. Depositions using high-fluence (6 J/cm2) low pressure (10−2 mbar) provide the optimal ratio in LBMO samples. Deviations from stoichiometry are observed when decreasing or increasing background This behavior is...
We investigate the effects of layer thickness and uniformity in solid oxide fuel cells with Gd0.1Ce0.9O1.95-δ buffer layers deposited by room temperature sputtering followed air annealing. Buffer different (in range 200–400 nm) have been using two configurations resulting coverage thin layers. By comparing electrochemical performances at temperatures sputtered screen printed assembled same short stack, we observed improvements, particularly lower temperatures, all analysed properties...
We report on structural, magnetic, and transport properties of LaxMnO3−δ (LMO) thin films, epitaxially grown SrTiO3 substrates by molecular beam epitaxy. Transport were investigated as a function the La/Mn stoichiometry oxygen content. Optimal oxygenated LMO films (with ratio La/Mn=0.88) show metal-insulator transitions temperature TMI∼387 K magnetotransport similar to those found in strontium-doped La1−xSrxMnO3 manganites compounds. Also presence slight unbalance (namely, x=0.98), very high...
Oxygen $1s\ensuremath{\rightarrow}2p$ (K-edge) x-ray absorption spectra mimic the density of metalliclike states transition metal oxides, thus shedding light on electronic band structure near Fermi energies these compounds. We take here advantage linear dichroism measurements at O K edge different (SrMnO${}_{3}$)${}_{n}$(LaMnO${}_{3}$)${}_{2n}$ superlattices, SrMnO${}_{3}$ and LaMnO${}_{3}$ thin films. X-ray dichroism, in pre-edge region spectra, provides evidence about specific symmetry Mn...
GaAs-based photocathodes are the state-of-the-art in production of highly spin-polarized electron beams for accelerator and microscopy applications. While various novel structures GaAs have been shown to increase degree polarization quantum efficiency, all require activation negative affinity (NEA) operate at photon energies where highest spin is achieved. In this work, we report on NEA bulk performed using Sb-Cs-O. We show layer be more robust with respect traditional Cs O terms charge...
Alkali antimonide photocathodes are capable of generating high brightness electron beams given their quantum efficiency and low mean transverse energy (MTE). Increasing the photoemitted beyond current state art requires surface control photocathode at atomic scale, since beam cathode is degraded by a rough, inhomogeneous surface. In this work, we grow cesium on single crystal substrates (Al2O3, TiO2, 3C–SiC, sample Si) study resulting morphology with scanning tunneling microscopy (STM). We...
The transport and noise properties of ${\text{Pr}}_{0.7}{\text{Ca}}_{0.3}{\text{MnO}}_{3}$ epitaxial thin films in the temperature range from room to 160 K are reported. It is shown that both broadband $1/f$ dependence resistance on electric field consistent with idea a collective electrical transport, as classical model sliding charge density waves. On other hand, observations cannot be reconciled standard models ordering melting. Methodologically, it proposed consider noise-spectra...
Superconducting Sr1–xLaxCuO2 thin films have been grown on GdScO3 substrates by reflection high-energy electron diffraction calibrated layer-by-layer molecular-beam epitaxy. X-ray analysis has confirmed the infinite layer structure after an in situ vacuum annealing step. In photoemission spectroscopy indicates that step employed immediately film growth to achieve superconducting results oxygen loss from films. The critical temperature depends La content x, with highest value obtained for...
La${}_{0.65}$Sr${}_{0.35}$MnO${}_{\text{3-}\ensuremath{\delta}}$ (LSMO) films ($\ensuremath{\delta}\ensuremath{\approx}$ 0, 0.07, 0.12) were studied by hard x-ray photoelectron spectroscopy. It is found that the Mn $3d$ valence band states shift to higher binding energies for oxygen-deficient samples, while their overall width decreases as a result of reduced density charge carriers. The concurrent disappearance well-screened state at $2p$ level indicates decrease in hybridization and...
The transport properties of manganite thin films characterized by a weak-localization transition have been studied. Detailed voltage noise measurements show specific $1/f$ spectrum below the temperature. A theoretical interpretation in terms universal conductance fluctuations explains nature unconventional electric noise, suggesting direct connection between phenomenon and fluctuations. mechanism allows its detection different systems under regime.
Abstract Two-dimensional materials, such as graphene, topological insulators, and two-dimensional electron gases, represent a technological playground to develop coherent electronics. In these systems, quantum interference effects in particular weak localization, are likely occur. These coherence usually characterized by well-defined features dc electrical transport, resistivity increase negative magnetoresistance below crossover temperature. Recently, it has been shown that magnetic...