Journals
2016 EN
Prosenjit Ghosh · Mikhail V. Vasiliev · Parthasarathi Ghosh
+6 more
Approximately 140 million years ago, the Indian plate separated from Gondwana and migrated by almost 90° latitude to its current location, forming the Himalayan-Tibetan system. Large discrepancies exist in the rate of migration of Indian plate during Phanerozoic. Here we describe a new approach to paleo-latitudinal reconstruction based on simultaneous determination of carbonate formation temperature and δ 18 O of soil carbonates, constrained by the abundances of 13 C- 18 O bonds in palaeosol carbonates. Assuming that the palaeosol carbonates have a strong relationship with the composition of the meteoric water, δ 18 O carbonate of palaeosol can constrain paleo-latitudinal position. Weighted mean annual rainfall δ 18 O water values measured at several stations across the southern latitudes are used to derive a polynomial equation: δ 18 Ow = −0.006 × (LAT) 2 − 0.294 × (LAT) − 5.29 which is used for latitudinal reconstruction. We use this approach to show the northward migration of the Indian plate from 46.8 ± 5.8°S during the Permian (269 M.y.) to 30 ± 11°S during the Triassic (248 M.y.), 14.7 ± 8.7°S during the early Cretaceous (135 M.y.), and 28 ± 8.8°S during the late Cretaceous (68 M.y.). Soil carbonate δ 18 O provides an alternative method for tracing the latitudinal position of Indian plate in the past and the estimates are consistent with the paleo-magnetic records which document the position of Indian plate prior to 135 ± 3 M.y.
Journals
2016 EN
Dmitry V. Averyanov · Christina G. Karateeva · Igor A. Karateev
+5 more
Control and manipulation of the spin of conduction electrons in industrial semiconductors such as silicon are suggested as an operating principle for a new generation of spintronic devices. Coherent injection of spin-polarized carriers into Si is a key to this novel technology. It is contingent on our ability to engineer flawless interfaces of Si with a spin injector to prevent spin-flip scattering. The unique properties of the ferromagnetic semiconductor EuO make it a prospective spin injector into silicon. Recent advances in the epitaxial integration of EuO with Si bring the manufacturing of a direct spin contact within reach. Here we employ transmission electron microscopy to study the interface EuO/Si with atomic-scale resolution. We report techniques for interface control on a submonolayer scale through surface reconstruction. Thus we prevent formation of alien phases and imperfections detrimental to spin injection. This development opens a new avenue for semiconductor spintronics.
Journals
2016 EN
M. B. Gongalsky · Л. А. Осминкина · António B. Pereira
+8 more
Crystalline silicon (Si) nanoparticles present an extremely promising object for bioimaging based on photoluminescence (PL) in the visible and near-infrared spectral regions, but their efficient PL emission in aqueous suspension is typically observed after wet chemistry procedures leading to residual toxicity issues. Here, we introduce ultrapure laser-synthesized Si-based quantum dots (QDs), which are water-dispersible and exhibit bright exciton PL in the window of relative tissue transparency near 800 nm. Based on the laser ablation of crystalline Si targets in gaseous helium, followed by ultrasound-assisted dispersion of the deposited films in physiological saline, the proposed method avoids any toxic by-products during the synthesis. We demonstrate efficient contrast of the Si QDs in living cells by following the exciton PL. We also show that the prepared QDs do not provoke any cytoxicity effects while penetrating into the cells and efficiently accumulating near the cell membrane and in the cytoplasm. Combined with the possibility of enabling parallel therapeutic channels, ultrapure laser-synthesized Si nanostructures present unique object for cancer theranostic applications.
Journals
2016 EN
Anastasia M. Alekseeva · Oleg A. Drozhzhin · Kirill A. Dosaev
+9 more
The superconducting transition temperature ( T c ) of tetragonal Fe 1+δ Se was enhanced from 8.5 K to 44 K by chemical structure modification. While insertion of large alkaline cations like K or solvated lithium and iron cations in the interlayer space, the [Fe 2 Se 2 ] interlayer separation increases significantly from 5.5 Å in native Fe 1+δ Se to >7 Å in K x Fe 1− y Se and to >9 Å in Li 1− x Fe x (OH)Fe 1− y Se, we report on an electrochemical route to modify the superconducting properties of Fe 1+δ Se. In contrast to conventional chemical (solution) techniques, the electrochemical approach allows to insert non-solvated Li + into the Fe 1+δ Se structure which preserves the native arrangement of [Fe 2 Se 2 ] layers and their small separation. The amount of intercalated lithium is extremely small (about 0.07 Li + per f.u.), however, its incorporation results in the enhancement of T c up to ∼44 K. The quantum-mechanical calculations show that Li occupies the octahedrally coordinated position, while the [Fe 2 Se 2 ] layers remain basically unmodified. The obtained enhancement of the electronic density of states at the Fermi level clearly exceeds the effect expected on basis of rigid band behavior.
Journals
2016 EN
Dmitry V. Averyanov · Andrey M. Tokmachev · Christina G. Karateeva
+7 more
Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi 2 /Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n -Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics.
Journals
2016 EN
Mikhail Vasiliev · Ramzy Alghamedi · Mohammad NurEAlam
+1 more
Transparent energy-harvesting windows are emerging as practical building-integrated photovoltaics (BIPV), capable of generating electricity while simultaneously reducing heating and cooling demands. By incorporating spectrally-selective diffraction gratings as light deflecting structures of high visible transparency into lamination interlayers and using improved spectrally-selective thin-film coatings, most of the visible solar radiation can be transmitted through the glass windows with minimum attenuation. At the same time, the ultraviolet (UV) and a part of incident solar infrared (IR) radiation energy are converted and/or deflected geometrically towards the panel edge for collection by CuInSe 2 solar cells. Experimental results show power conversion efficiencies in excess of 3.04% in 10 cm × 10 cm vertically-placed clear glass panels facing direct sunlight, and up to 2.08% in 50 cm × 50 cm installation-ready framed window systems. These results confirm the emergence of a new class of solar window system ready for industrial application.
Journals
2016 EN
S. Sheludiakov · J. Ahokas · J. Järvinen
+6 more
We report on the first ESR study of atomic hydrogen and tritium stabilized ina solid T$_{2}$ and T$_{2}$:H$_{2}$ matrices down to 70$\,$mK. Theconcentrations of T atoms in pure T$_{2}$ approached $2\times10^{20}$cm$^{-3}$and record-high concentrations of H atoms $\sim1\times10^{20}$cm$^{-3}$ werereached in T$_{2}$:H$_{2}$ solid mixtures where a fraction of T atoms becameconverted into H due to the isotopic exchange reaction T+H$_2\rightarrow$TH+H.The maximum concentrations of unpaired T and H atoms was limited by theirrecombination which becomes enforced by efficient atomic diffusion due to apresence of a large number of vacancies and phonons generated in the matricesby $\beta$-particles. Recombination also appeared in an explosive manner bothbeing stimulated and spontaneously in thick films where sample cooling wasinsufficient. We suggest that the main mechanism for H and T migration isphysical diffusion related to tunneling or hopping to vacant sites in contrastto isotopic chemical reactions which govern diffusion of H and D atoms createdin H$_{2}$ and D$_{2}$ matrices by other methods.
Royal Society of Chemistry
Journals
2016 EN
М. С. Пширков · V. V. Vasiliev · К. А. Постнов
We have searched for an extended high-energy gamma-ray emission around the nearby giant spiral Andromeda galaxy M31 using almost 7 years of Fermi LAT data at energies above 300 MeV. The presence of a diffuse gamma-ray halo with total photon flux 2:6±0:6×10−9 cm−2 s−1, corresponding to a luminosity (0.3-100 GeV) of (3:2±0:6)×1038 erg s−1 (for a distance of 780 kpc) was found at a 5.3σ confidence level. The best-fit halo template corresponds to two 6-7.5 kpc bubbles symmetrically located perpendicular to the M31 galactic disc, similar to the ‘Fermi bubbles’ found around the Milky Way centre
Journals
2016 EN
С. Н. Николаев · Anna Semisalova · V. V. Rylkov
+14 more
The results of a comprehensive study of magnetic, magneto-transport and structural properties of nonstoichiometric MnxSi1-x (x ≈ 0.51-0.52) films grown by the Pulsed Laser Deposition (PLD) technique onto Al2O3(0001) single crystal substrates at T = 340°C are present. A highlight of used PLD method is the non-conventional (“shadow”) geometry with Kr as a scattering gas during the sample growth. It is found that the films exhibit high-temperature (HT) ferromagnetism (FM) with the Curie temperature TC ∼ 370 K accompanied by positive sign anomalous Hall effect (AHE); they also reveal the polycrystalline structure with unusual distribution of grains in size and shape. It is established that HT FM order is originated from the bottom interfacial self-organizing nanocrystalline layer. The upper layer adopted columnar structure with the lateral grain size ≥50 nm, possesses low temperature (LT) type of FM order with Tc ≈ 46 K and contributes essentially to the magnetization at T ≤ 50 K. Under these conditions, AHE changes its sign from positive to negative at T ≤ 30K. We attribute observed properties to the synergy of distribution of MnxSi1-x crystallites in size and shape as well as peculiarities of defect-induced FM order in shadow geometry grown polycrystalline MnxSi1-x (x ∼ 0.5) films
American Institute of Physics
Conference Proceedings
2016 EN
PANDA Collaboration B. Singh · W. Erni · B. Krusche
+501 more
The results of simulations for future measurements of electromagnetic form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision at which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e. the $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistic and systematic uncertainties on the extracted proton form factors are evaluated using to the two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam condition and detector performances.
American Institute of Physics