343 research outputs found
Tc=21K in epitaxial FeSe0.5Te0.5 thin films with biaxial compressive strain
High purity epitaxial FeSe0.5Te0.5 thin films with different thickness were
grown by Pulsed Laser Ablation on different substrates. By varying the film
thickness, Tc up to 21K were observed, significantly larger than the bulk
value. Structural analyses indicated that the a axis changes significantly with
the film thickness and is linearly related to the Tc. The latter result
indicates the important role of the compressive strain in enhancing Tc. Tc is
also related to both the Fe-(Se,Te) bond length and angle, suggesting the
possibility of further enhancement
Temperature- and doping-dependent nanoscale Schottky barrier height at the Au/Nb:SrTiO3interface
We use ballistic electron emission microscopy to investigate prototypical Au/Nb-doped SrTiO3(NSTO) Schottky barrier diodes for different temperatures and doping levels. To this end, ultrathin Au overlayers are thermally evaporated onto TiO2-terminated NSTO single crystal substrates. We show that at room temperature, regardless of the nominal doping, rectification is controlled by a spatially inhomogeneous Schottky barrier height (SBH), which varies on a length scale of tens of nanometers according to a Gaussian distribution with a mean value of 1.29-1.34 eV and the standard deviation in the range of 80-100 meV. At lower temperatures, however, doping effects become relevant. In particular, junctions with a low Nb content of 0.01 and 0.05 wt. % show an 3c300 meV decrease in the mean SBH from room temperature to 80 K, which can be explained by an electrostatic analysis assuming a temperature-dependent dielectric permittivity for NSTO. In contrast, this model fails to predict the weaker temperature dependence of SBH for junctions based on 0.5 wt. % NSTO. Our nanoscale investigation demands to reassess conventional models for the NSTO polarizability in high-intensity electric fields. Furthermore, it contributes to the comprehension and prediction of transport in metal/SrTiO3junctions and devices
Microscopic analysis of the chemical reaction between Fe(Te,Se) thin films and underlying CaF
To understand the chemical reaction at the interface of materials, we
performed a transmission electron microscopy (TEM) observation in four types of
Fe(Te,Se) superconducting thin films prepared on different types of substrates:
CaF2 substrate, CaF2 substrate with a CaF2 buffer layer, CaF2 substrate with a
FeSe buffer layer, and a LaAlO3 substrate with a CaF2 buffer layer. Based on
the energy-dispersive X-ray spectrometer (EDX) analysis, we found possible
interdiffusion between fluorine and selenium that has a strong influence on the
superconductivity in Fe(Te,Se) films. The chemical interdiffusion also plays a
significant role in the variation of the lattice parameters. The lattice
parameters of the Fe(Te,Se) thin films are primarily determined by the chemical
substitution of anions, and the lattice mismatch only plays a secondary role.Comment: 30 pages, 9 figur
Highly effective and isotropic pinning in epitaxial Fe(Se,Te) thin films grown on CaF2 substrates
We report on the isotropic pinning obtained in epitaxial Fe(Se,Te) thin films
grown on CaF2 (001) substrate. High critical current density values larger than
1 MA/cm2 in self field in liquid helium are reached together with a very weak
dependence on the magnetic field and a complete isotropy. Analysis through
Transmission Electron Microscopy evidences the presence of defects looking like
lattice disorder at a very small scale, between 5 and 20 nm, which are thought
to be responsible for such isotropic behavior in contrast to what observed on
SrTiO3, where defects parallel to the c-axis enhance pinning in that directio
Ecological implications beyond the ecotoxicity of plastic debris on marine phytoplankton assemblage structure and functioning
none7noPlastic pollution is a global issue posing a threat to marine biota with ecological implications on ecosystem
functioning. Micro and nanoplastic impact on phytoplankton autotrophic species (e.g., cell growth inhibition,
decrease in chlorophyll a and photosynthetic efficiency and hetero-aggregates formation) have been largely
documented. However, the heterogeneity of data makes rather difficult a comparison based on size (i.e. micro vs
nano). In addition, knowledge gaps on the ecological impact on phytoplankton assemblage structure and
functioning are evident. A new virtual meta-analysis on cause-effect relationships of micro and nanoplastics on
phytoplankton species revealed the significant effect posed by polymer type on reducing cell density for tested
PVC, PS and PE plastics. Linked with autotrophic phytoplankton role in atmospheric CO2 fixation, a potential
impact of plastics on marine carbon pump is discussed. The understanding of the effects of microplastics and
nanoplastics on the phytoplankton functioning is fundamental to raise awareness on the overall impact on the
first level of marine food web. Interactions between micro and nanoplastics and phytoplankton assemblages have
been quite documented by in vitro examinations; but, further studies considering natural plankton assemblages
and/or large mesocosm experiments should be performed to evaluate and try predicting ecological impacts on
primary producers.openCasabianca Silvia, Bellingeri Arianna, Capellacci Samuela, Sbrana Alice, Russo Tommaso, Corsi Ilaria, Penna AntonellaCasabianca, Silvia; Bellingeri, Arianna; Capellacci, Samuela; Sbrana, Alice; Russo, Tommaso; Corsi, Ilaria; Penna, Antonell
Impact of polystyrene nanoparticles on marine diatom Skeletonema marinoi chain assemblages and consequences on their ecological role in marine ecosystems.
Marine diatoms have been identified among the most abundant taxa of microorganisms associated with plastic waste collected at sea. However, the impact of nano-sized plastic fragments (nanoplastics) at single cell and population level is almost unknown. We exposed the marine diatom Skeletonema marinoi to model polystyrene nanoparticles with carboxylic acid groups (PS-COOH NPs, 90 nm) for 15 days (1, 10, 50 mu g/mL). Growth, reactive oxygen species (ROS) production, and nano-bio-interactions were investigated. No effect on diatom growth was observed, however Dynamic light scattering (DLS) demonstrated the formation of large PS aggregates which were localized at the diatoms' fultoportula process (FPP), as shown by TEM images. Increase production of ROS and reduction in chain length were also observed upon PS NPs exposure (p < 0.005). The observed PS-diatom interaction could have serious consequences on diatoms ecological role on the biogeochemical cycle of carbon, by impairing the formation of fast-sinking aggregates responsible for atmospheric carbon fixation and sequestration in the ocean sea floor. S. marinoi exposure to PS NPs caused an increase of intracellular and extracellular oxidative stress, the reduction of diatom's chain length and the adhesion of PS NPs onto the algal surface
Egg yolk antibodies and nanotechnology applied to animal health and production
Nanotechnology is a rapidly developing area of science and technology, which deals with the application, production and processing of materials with sizes less than 100nm (a nanometer being one billionth of a meter). In addition, it is an interdisciplinary science comprising of various disciplines such as physics, chemistry, electronics, material science, health science, biology, and veterinaryscience, and it has impact on many industriesFil: Bellingeri, Romina Valeria. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Anatomía Animal. Laboratorio de Biotecnología Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Picco, Natalia Yanina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Anatomía Animal. Laboratorio de Biotecnología Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Alustiza, Fabrisio Eduardo. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Anatomía Animal. Laboratorio de Biotecnología Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Grosso, Maria Carolina. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Anatomía Animal. Laboratorio de Biotecnología Animal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Vivas, A.. Universidad Nacional de Río Cuarto. Facultad de Agronomía y Veterinaria. Departamento de Anatomía Animal. Laboratorio de Biotecnología Animal; Argentin
Influence of free charge carrier density on the magnetic behavior of (Zn,Co)O thin film studied by Field Effect modulation of magnetotransport
The origin of (ferro)magnetic ordering in transition metal doped ZnO is a still open question. For applications it is fundamental to establish if it arises from magnetically ordered impurity clusters embedded into the semiconducting matrix or if it originates from ordering of magnetic ions dilute into the host lattice. In this latter case, a reciprocal effect of the magnetic exchange on the charge carriers is expected, offering many possibilities for spintronics applications. In this paper we report on the relationship between magnetic properties and free charge density investigated by using Zinc oxide based field effect transistors, in which the charge carrier density is modulated by more than 4 order of magnitude, from 10(16) to 10(20) e(-)/cm(3). The magnetotransport properties are employed to probe the magnetic status of the channel both in pure and cobalt doped zinc oxide transistors. We find that it is widely possible to control the magnetic scattering rates by field effect. We believe that this finding is a consequence of the modulation of magnetization and carrier spin polarization by the electric field. The observed effects can be explained by the change in size of bound magnetic polarons that induces a percolation magnetic ordering in the sample
Thermal properties of SmFeAs(O1-xFx) as probe of the interplay between electrons and phonons
A comparative study of thermal properties of SmFeAsO, SmFeAs(O0.93F0.07) and
SmFeAs(O0.85F0.15) samples is presented. Specific heat and thermal conductivity
show clear evidences of the spin density wave (SDW) ordering below TSDW 135 K
in undoped SmFeAsO. At low level of F-doping, SmFeAs(O0.93F0.07), SDW ordering
is suppressed and superconducting features are not yet optimally developed in
both specific heat and thermal conductivity. At optimal level of F-doping
SmFeAs(O0.85F0.15) anomalies related to the superconducting transition are well
noticeable. By a compared analysis of doped and undoped samples we conclude
that, despite F-doping modifies definitely the electronic ground state, it does
not substantially alter phonon and electron parameters, like phonon modes,
Sommerfeld coefficient, electro-phonon coupling. The analysis of the thermal
conductivity curves provides an evaluation of SDW and superconducting energy
gap, showing that phonons can suitably probe features of electronic ground
state
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