Search results for "ELA"
showing 10 items of 33899 documents
Stabilization of primary mobile radiation defects in MgF2 crystals
2016
Abstract Non-radiative decay of the electronic excitations (excitons) into point defects ( F – H pairs of Frenkel defects) is main radiation damage mechanism in many ionic (halide) solids. Typical time scale of the relaxation of the electronic excitation into a primary, short-lived defect pair is about 1–50 ps with the quantum yield up to 0.2–0.8. However, only a small fraction of these primary defects are spatially separated and survive after transformation into stable, long-lived defects. The survival probability (or stable defect accumulation efficiency) can differ by orders of magnitude, dependent on the material type; e.g. ∼10% in alkali halides with f.c.c. or b.c.c. structure, 0.1% in…
Analysis of thin high-k and silicide films by means of heavy ion time-of-flight forward-scattering spectrometry
2006
The use of forward scattered heavy incident ions in combination with a time-of-flight-energy telescope provides a powerful tool for the analysis of very thin (5–30 nm) films. This is because of greater stopping powers and better detector energy resolution for heavier ions than in conventional He-RBS. Because of the forward scattering angle, the sensitivity is greatly enhanced, thus reducing the ion beam induced desorption during the analysis of very thin films. The drawback of forward scattering angle is the limited mass separation for target elements. We demonstrate the performance of the technique with the analysis of 25 nm thick NiSi films and atomic layer deposited 6 nm thick HfxSiyOz f…
Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks
2017
In this work we focus on magnetic relaxation in Mn80Ir20(12 nm)/Cu(6 nm)/Py(dF) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM) multilayers with different thickness of the ferromagnetic permalloy layer. An effective FM-AFM interaction mediated via the conduction electrons in the nonmagnetic Cu spacer – the spin-pumping effect – is detected as an increase in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of the resonant magnetic field. We further find experimentally that the spin-pumping-induced contribution to the linewidth is inversely proportional to the thickness of the Py layer. We show that this thickness dependence likely originates from the dissipative dynamics of …
Influence of Sr addition on structural, dielectric and Raman properties of Na0.5Bi0.5TiO3ceramics
2016
ABSTRACTLead free (Na0.5Bi0.5)1-xSrxTiO3 (x = 0, 0.01 and 0.02) ceramics were produced by a conventional solid-state sintering method. X-ray diffraction analysis shows that the obtained samples possess the perovskite structure with rhombohedral symmetry. The microstructure study shows a dense structure, in agreement with the relative density (above 97%). Dielectric analysis revealed the diffuse character of the electric permittivity anomalies and their shift to a lower temperature range after Sr doping of NBT. The Raman spectra are similar for all samples in agreement with the X-ray diffraction data. The possible origin of the observed effects was discussed.
Domain Walls Motions in Barium Titanate Ceramics
1996
The shear modulus and mechanical loss at low frequencies (0.01, 0.3, 1 Hz) are measured by an inverted pendulum for BaTiO 3 ceramic with large grain sizes. The permittivity and dielectric losses are also investigated for the same material at higher frequencies between 1 and 100 kHz as function of temperature. Those results show several relaxation peaks in the ferroelectric phases. The activation energy of each peak is obtained to be 0.29, 0.45, 0.68, 0.92 eV. The influences of strain amplitude and thermal treatments are studied specially for the mechanical relaxation peak located in the tetragonal phase. All the relaxation peaks could be associated to the interaction of oxygen vacancies in …
Raman spectra and anomalies of dielectric properties and thermal expansion of lead-free (1−x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.08 and 0.1) ceramics
2016
ABSTRACTThermal expansion, Raman and dielectric properties of the lead-free (1−x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.08 and 0.1) ceramic solid solutions, fabricated by the conventional solid-state reaction method, were investigated. The Sr-doping results in an increase of the dielectric permittivity, broadening of the permittivity maximum, enhancement of the relaxation near depolarization temperature, broadening of the Raman bands and shift of all anomalies toward lower temperatures. The observed effects are attributed to an increase of the degree of cationic disorder and enhancement of the relaxor-like features. Anomalies in the thermal expansion strain were observed at the temperatures corre…
Dielectric, thermal and Raman spectroscopy studies of lead-free (Na0.5Bi0.5)1−xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics
2016
ABSTRACTLead-free (Na0.5Bi0.5)1−xSrxTiO3 (x = 0, 0.04 and 0.06) ceramics with relative densities above 97% were prepared by solid-state synthesis process. Their dielectric, thermal and Raman properties were studied. X-ray diffraction analysis shows perovskite structure with rhombohedral symmetry at room temperature. Sr doping of Na0.5Bi0.5TiO3 (NBT) results in an increase of the dielectric permittivity, diffusing of the permittivity maximum and its shift toward lower temperatures. The temperature of the rhombohedral–tetragonal phase transition indicated by the differential scanning calorimetry (DSC) peak and relaxational dielectric anomaly near the depolarization temperature are also shifte…
Two-phase dielectric polar structures in 0.1NBT-0.6ST-0.3PT solid solutions
2018
Abstract In this work we address the peculiarities of the macroscopic responses in ternary 0.1Na0·5Bi0·5TiO3-0.6SrTiO3-0.3PbTiO3 (0.1NBT-0.6ST-0.3PT) solid solutions. These solid solutions exhibit a spontaneous first order relaxor to normal ferroelectric phase transition. The phase transition is accompanied by a broad dielectric relaxation which expands over 10 orders of magnitude in frequency just above the phase transition temperature. The temperature dependence of polarization shows that non-zero net polarization persists above the phase transition temperature. Below the phase transition temperature, it is not possible to describe the temperature dependence of polarization with a power l…
Structural phase transition in [(C2H5)4N][(CH3)4N]ZnCl4
2019
The hybrid crystal [(C2H5)4N][(CH3)4N]ZnCl4 was studied using several experimental methods. DSC studies revealed the first order phase transition to the high temperature phase at about 496 K. This phase transition was confirmed in dielectric studies. Optical observation revealed the domain structure appearance characteristic for that of the phase transition between tetragonal and orthorhombic phases. This phase transition shows a lowering of symmetry as in the case of bromide analogs. Additionally, the optical studies showed the appearance of a number of cracks in the sample and in some cases, the samples became milky after cooling from the high temperature to the room temperature phase.
Compact setup for spin-, time-, and angle-resolved photoemission spectroscopy.
2020
Review of scientific instruments 91(6), 063001 (2020). doi:10.1063/5.0004861