51 research outputs found
One-step preparation of N-doped strontium titanate films by pulsed laser deposition
Perovskite-type oxynitrides exhibit promising electrical and optical properties and can possibly be used in the future as functional materials for electrical, photo-, and electrochemical applications. Continuous heterovalent substitution of oxygen ions by nitrogen ions allows tuning of the desired optical and/or electronic properties to the application specifications. In the present work deposition of SrTiO3:N films by pulsed reactive crossed beam laser ablation was studied in order to examine the influence of different deposition parameters on the film crystallinity and composition. The deposited films exhibit a perovskite-type crystal structure and reveals epitaxial growth on MgO(100) substrates. The unit cell parameters of the deposited SrTiO3:N films range within , which is slightly larger than for polycrystalline SrTiO3 (a=3.905). The studied films reveal an oxygen content in the range of (2.70-2.98)±0.15. The relative N content (vs. O) can be tuned within the range of 1.0-3.0% by adjusting the deposition parameters. The N:O concentration ratio increases with increasing laser fluence and target-to-substrate distances, while the substrate temperature has a more complex influence on the nitrogen concentration. In the range of 580-650°C the [N]/[O] ratio increases while further heating results in a gradual decrease of the N conten
Pulsed laser deposition growth of heteroepitaxial YBa2Cu3O7/La0.67Ca0.33MnO3 superlattices on NdGaO3 and Sr0.7La0.3Al0.65Ta0.35O3 substrates
Heteroepitaxial superlattices of [YBa2Cu3O7(n)/ La0.67Ca0.33MnO3(m)]x, where
n and m are the number of YBCO and LCMO monolayers and x the number of bilayer
repetitions, have been grown with pulsed laser deposition on NdGaO3 (110) and
Sr0.7La0.3Al0.65Ta0.35O3 (LSAT) (001). These substrates are well lattice
matched with YBCO and LCMO and, unlike the commonly used SrTiO3, they do not
give rise to complex and uncontrolled strain effects due to structural
transitions at low temperature. The growth dynamics and the structure have been
studied in-situ with reflection high energy electron diffraction (RHEED) and
ex-situ with scanning transmission electron microscopy (STEM), x-ray
diffraction, and neutron reflectometry. The individual layers are found to be
flat and continuous over long lateral distances with sharp and coherent
interfaces and with a well-defined thickness of the individual layer. The only
visible defects are antiphase boundaries in the YBCO layers that originate from
perovskite unit cell height steps at the interfaces with the LCMO layers. We
also find that the first YBCO monolayer at the interface with LCMO has an
unusual growth dynamics and is lacking the CuO chain layer while the subsequent
YBCO layers have the regular Y-123 structure. Accordingly, the CuO2 bilayers at
both the LCMO/YBCO and the YBCO/LCMO interfaces are lacking one of their
neighboring CuO chain layers and thus half of their hole doping reservoir.
Nevertheless, from electric transport measurements on asuperlattice with n=2 we
obtain evidence that the interfacial CuO2 bilayers remain conducting and even
exhibit the onset of a superconducting transition at very low temperature.
Finally, we show from dc magnetization and neutron reflectometry measurements
that the LCMO layers are strongly ferromagnetic
RF-plasma assisted pulsed laser deposition of nitrogen-doped SrTiO3 thin films
Perovskite-type nitrogen substituted SrTiO3 thin films were deposited with a one-step process by RF-plasma assisted pulsed laser deposition from a SrTiO3 target using a N2 plasma, while deposition with a NH3 plasma yields films with almost no incorporated nitrogen. The deposited films exhibit a cubic perovskite-type crystal structure and reveal oriented growth on MgO(100) substrates. The unit cell parameters of the studied N-doped SrTiO3 films range within 3.905<a<3.918Å, which is slightly larger than for SrTiO3 (a=3.905Å). The nitrogen content in the deposited films varies from 0.2 to 0.7atom%. The amount of incorporated nitrogen in the films decreases with increasing RF-power, while the N2 flow rate does not have any pronounced influence on the N content. Nitrogen incorporation results in an increased optical absorption at 400-600nm, which is associated with N(2p) energy states that have a higher energy level than the valence band in strontium titanate. The optical band gap energies in the studied N-doped SrTiO3 films are at 3.2-3.3eV, which is very similar to that of pure strontium titanate (∼3.2eV). Films deposited with NH3 for the RF-plasma exhibit a lower degree of crystallinity and reveal almost no nitrogen incorporation into the crystal lattic
Depth profile of the ferromagnetic order in a YBaCuO / LaCaMnO superlattice on a LSAT substrate: a polarized neutron reflectometry study
Using polarized neutron reflectometry (PNR) we have investigated a
YBa2Cu3O7(10nm)/La2/3Ca1/3MnO3(9nm)]10 (YBCO/LCMO) superlattice grown by pulsed
laser deposition on a La0.3Sr0.7Al0.65Ta0.35O3 (LSAT) substrate. Due to the
high structural quality of the superlattice and the substrate, the specular
reflectivity signal extends with a high signal-to-background ratio beyond the
fourth order superlattice Bragg peak. This allows us to obtain more detailed
and reliable information about the magnetic depth profile than in previous PNR
studies on similar superlattices that were partially impeded by problems
related to the low temperature structural transitions of the SrTiO3 substrates.
In agreement with the previous reports, our PNR data reveal a strong magnetic
proximity effect showing that the depth profile of the magnetic potential
differs significantly from the one of the nuclear potential that is given by
the YBCO and LCMO layer thickness. We present fits of the PNR data using
different simple block-like models for which either a ferromagnetic moment is
induced on the YBCO side of the interfaces or the ferromagnetic order is
suppressed on the LCMO side. We show that a good agreement with the PNR data
and with the average magnetization as obtained from dc magnetization data can
only be obtained with the latter model where a so-called depleted layer with a
strongly suppressed ferromagnetic moment develops on the LCMO side of the
interfaces. The models with an induced ferromagnetic moment on the YBCO side
fail to reproduce the details of the higher order superlattice Bragg peaks and
yield a wrong magnitude of the average magnetization. We also show that the PNR
data are still consistent with the small, ferromagnetic Cu moment of 0.25muB
that was previously identified with x-ray magnetic circular dichroism and x-ray
resonant magnetic reflectometry measurements on the same superlattice.Comment: 11 pages, 7 figure
Оценка эффекта от внедрения информационных технологий белорусским бизнесом
The main purpose of the article is to analyze the effect of the information technologies (IT) usage by Belarusian SMEs based on a sample survey of CEOs from 424 entities. The study showed that, in general, business processes automation brings positive effects; in particular, IT can improve interaction with suppliers, contractors and banks, as well as, in general, increases the enterprise competitiveness. The correlation results demonstrate how organizational factors are associated with the management's assessment of the IT impact both on general performance and on specific business processes. In the conclusion, the policy implications on stimulating the IT usage by Belarusian enterprises are presented.. Основной целью статьи является анализ эффекта от использования информационных технологий (далее - ИТ) белорусскими малыми и средними предприятиями (далее - МСП) на основе выборочного опроса руководителей 424 субъектов. Исследование показало, что в основном эффект от внедрения информационных технологий для автоматизации бизнес-процессов оценивается положительно, в частности, ИТ позволяют улучшить взаимодействие с поставщиками, подрядчиками и банками, а также в целом повысить конкурентоспособность предприятия. Результаты корреляционного анализа демонстрируют, как организационные факторы связаны с оценкой руководством влияния ИТ на показатели деятельности предприятия, а также на отдельные бизнес-процессы. В заключении представлены рекомендации государственным органам по стимулированию внедрения и использования ИТ белорусскими предприятиями
Magnetic Proximity Effect in YBa₂Cu₃O₇/La<sub>2/3</sub>Ca<sub>1/3</sub>MnO₃ and YBa₂Cu₃O₇/LaMnO₃₊ Superlattices
Using neutron reflectometry and resonant x-ray techniques we studied the magnetic proximity effect (MPE) in superlattices composed of superconducting YBa₂Cu₃O₇ and ferromagnetic-metallic La0.67Ca0.33MnO₃ or ferromagnetic-insulating LaMnO₃₊. We find that the MPE strongly depends on the electronic state of the manganite layers, being pronounced for the ferromagnetic-metallic La0.67Ca0.33MnO₃ and almost absent for ferromagnetic-insulating LaMnO₃₊. We also detail the change of the magnetic depth profile due to the MPE and provide evidence for its intrinsic nature
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