107 research outputs found
Continuous wave OSL in bulk AlN single crystals
The kinetics of recombination luminescence of β-irradiated AlN single crystals has been studied with continuous wave optically stimulated luminescence (CW-OSL) method. It is shown that the OSL process is characterized by two exponential components with a decay time τ = 32 and 212 s. Photoionization cross-sections σ = 4.8·10-19 and 7.3·10-20 cm2 have been evaluated, assuming each component is related to electron traps based on VN- and/or ON-centers at various charged states. It is established that dose dependences of the OSL response of the bulk crystals under study are linear with taking into correct accounting for the radiation induced afterglow and hence can be used for quantitative estimates in solid state dosimetry. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Dosimetric application of green luminescence in irradiated TLD-500 detectors
The spectral and kinetic characteristics of thermoluminescence (TL) for anion-defective α-Al2O3 single crystals in the 4.4-2.2 eV range at 300-600 K were studied. Three-dimensional (3D) plots of the luminescence under research for a sample before and after UV irradiation at 623 K for 30 min were analyzed. The increase in the emission response in the 2.4 and 3.7 eV bands for the sample after the photothermal treatment was observed. The dominant contribution of a thermally stimulated process with first-order kinetics in the regularities of the 2.4 eV luminescence was shown. The linearity of the dose dependences for the 2.4 eV TL response in different samples at 10-5-1 Gy was demonstrated. The advantage of using the green thermoluminescence in the TLD-500 for solid state dosimetry was discussed. © 2013 Elsevier B.V. All rights reserved
Nanostructural features of anodic zirconia synthesized using different temperature modes
Nanotubular and nanoporous structures of ZrO 2 were synthesized by potentiostatic anodization with varying the temperatures of anode in the range of T A = 0 - 90 °C and electrolyte in the range of T El = 20 - 50 °C. It was shown that difference between T A and T El had significant influence on growth rate and morphology type of zirconia nanostructures. Optimal parameters of thermal modes for nanotubular ZrO 2 synthesis were discussed. © 2018 Institute of Physics Publishing. All rights reserved.Act 211 Government of the Russian Federation, contract № 02.A03.21.0006, supported the study. R.V.K. thanks RFBR research project № 18-33-01072 for support. A.S.V. and I.A.W. thank Minobrnauki initiative research project № 16.5186.2017/8.9 for support
Temperature dependence of self-trapped exciton luminescence in nanostructured hafnia powder
The intrinsic optical properties and peculiarities of the energy structure of
hafnium dioxide largely determine the prospects for applying the latter in new
generation devices of optoelectronics and nanoelectronics. In this work, we
have studied the diffuse reflectance spectra at room temperature for a
nominally pure nanostructured powder with a monoclinic crystal
structure and, as well its photoluminescence in the temperature range of 40 -
300 K. We have also estimated the bandgap under the assumption made for
indirect (5.31 eV) and direct (5.61 eV) allowed transitions. We have detected
emission with a 4.2 eV maximum at T < 200 K and conducted an analysis of the
experimental dependencies to evaluate the activation energies of thermal
quenching (140 meV) and enhancement (3 meV) processes. Accounting for both the
temperature behavior of the spectral characteristics and the estimation of the
Huang-Rhys factor S >> 1 has shown that radiative decay of self-trapped
excitons forms the mechanism of the indicated emission. In this case, the
localization is mainly due to the interaction of holes with active vibrational
modes of oxygen atoms in non-equivalent ( and ) crystal
positions. Thorough study of the discussed excitonic effects can advance
development of hafnia-based structures with a controlled optical response.Comment: 21 pages, 7 figures, 2 tables, 56 references. Keywords: hafnium
dioxide, self-trapped exciton, F-center, thermal quenching of luminescence,
luminescence enhacement, Huang-Rhys factor, effective phonon energy, bandgap
widt
Luminescent and dosimetric properties of nanostructured ceramics based on aluminum oxide
The main features of thermoluminescence (TL) of nanostructured ceramics based on anion-defective aluminum oxide have been investigated. The kinetic parameters of the TL dosimetric peak at 475 K have been determined. The possibility of using nanostructured ceramics for beta-radiation dosimetry of high doses (up to 1 kGy) with thermoluminescence of deep traps has been justified. It has been found that the light sum of the dosimetric peak decreases with an increase in the heating rate due to the temperature quenching of the luminescence. The obtained results have confirmed that the mechanism of TL quenching in anion-defective aluminum oxide is associated with the temperature dependence of the probability of the capture in deep traps, which can be caused by thermal ionization of excited states of F-centers. © 2013 Pleiades Publishing, Ltd
Spectrally resolved thermoluminescence in UV excited hexagonal boron nitride nanopowder
Thermally stimulated luminescence (TSL) excitation and emission processes in h-BN nanopowders after UV irradiation were studied. TSL showed the highest response within the 5.4 eV band. 3.0 and 3.9 eV bands, resulting from the radiative donor-acceptor recombination between the electron (1B-H O N -centers) and the hole traps (CN-center), were found. TSL curves quantitative analysis in the context of general order kinetics was made. It was shown that 1B-centers had 0.850.05 eV activation energy and were responsible for the TSL peak at 35010 K. Band structure for TSL excitation and emission mechanisms in h-BN nanopowder was suggested. © Published under licence by IOP Publishing Ltd
Spectral and kinetic features of thermoluminescence in hexagonal boron nitride powder after UV-irradiation
Thermally stimulated luminescence (TL) from UV-irradiated h-BN powder synthesized using carbamide technique was studied. Three TL peaks at T max = 380, 500 and 600 K during linear heating with 2 K/s rate in RT - 773 K temperature range were observed. It was found that the 2.90 and 3.25 eV emission bands, which were related with recombination centers on the basis of VN and BO--complexes, dominate in TL spectra of h-BN. Experimental TL glow curves were analyzed in terms of general order kinetics and energy parameters of responsible capture levels were estimated. It was shown, considering the independent data on the luminescent properties of hexagonal boron nitride in different structural states, that TL peaks at 380 K and 600 K were due to traps based on the one-boron and the three-boron centers with thermal depth EA = 0.7 and 1.0 eV, respectively. The possible origin of the trap with EA = 1.6 eV, responsible for the TL peak at 500 K, is discussed. © 2013 Elsevier B.V. All rights reserved
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