Population change in Russia :

制度:新 ; 報告番号:甲2675号 ; 学位の種類:博士(人間科学) ; 授与年月日:2008/7/16 ; 早大学位記番号:新484

Luminescence of natural α-quartz crystal with aluminum, alkali and noble ions impurities

This work was supported by the Latvian Science Council Grant No lzp-2018/1–0289 .Photoluminescence and thermally stimulated luminescence of synthetic and natural (morion and smoky) α-quartz crystals doped with aluminum and alkali ions were studied. The samples were examined both untreated and subjected to substitution of alkali ions for copper or silver ions. The photoluminescence spectrum of the untreated crystals is characterized with the main blue band around 400 nm (~3.1 eV). The corresponding luminescence center is based on a defect containing aluminum and alkali as compensators in natural and synthetic quartz crystals. Photoluminescence is subjected to thermal quenching and can be detected at high temperatures above 700 K, however the main intensity decay takes place at 200 K. The thermal quenching activation energy is 0.15 ± 0.05 eV and the frequency factor is 3·107 s−1. In the samples with silver ions the main luminescence band is located at ~260 nm (~4.7 eV) with a time constant of ~37 μs at 80 K, and in the samples with copper ions the PL band is at ~ 360 nm (~3.4 eV) with a time constant ~ 50 μs at 80 K. The initial luminescence of crystals is greatly reduced after introduction of noble ions. The luminescence of noble ions quenches at 700 K without drop in intensity at 200 K. For luminescence associated with silver the energy of thermal quenching is 0.7 ± 0.1 eV with a frequency coefficient of 1 · 101 3 s−1, and for the luminescence related to copper, these parameters are 0.55 ± 0.1 eV and 1 · 101 2 s−1. The differences in intra-center luminescence properties of the same defect containing alkali ions or noble ions are based on differences in electronic transitions. In the case of alkali ions the charge transfer transitions between oxygen and alkali ions. In the case of noble ions absorption – luminescence corresponds to intra ion transitions. Radiation properties are related to trapping of an electron on one valence ion. Created atom moves out of aluminum containing defect. The hole remains on aluminum-oxygen defect. Thermally stimulated luminescence is related to release of atom, it diffusion to aluminum defect with the hole on oxygen and following radiative recombination. Optically stimulated luminescence is explained by the similar process of optical release of excited atom and movement to aluminum defect and recombination of electron with hole.Latvian Science Council Grant No lzp-2018/1–0289; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Photoelectric response of localized states in silica glass

This work was supported by the Latvian Science Council Grant No lzp-2018/1-0289.The photoelectric response of pure silica glasses excited by excimer lasers has been studied. The samples were made under various conditions. Photoelectric polarization of samples due to the Dember effect has been registered. The signal was recorded under the conditions of a space charge limited current. The space charge resulting from the capture of electrons and holes creates a static electric field that prevents diffusion of released charge carriers. The current registration in the external circuit stops, despite the continuation of photoexcitation. This effect was used as a fact of measuring the photocurrent in the sample volume instead of the parasitic current that is not associated with the sample. The screen has been chosen to prevent the influence of a spurious signal. It has been found that charge carriers are released when excited in the spectral absorption range of localized states of silica. Based on the Dember effect, the sign of the photoelectric response shows the type of charge carriers - an electron or a hole is mobile. Thus, a sample containing aluminum without alkali ions gives a negative signal, which indicates the diffusion of electrons at 290 K, since aluminum is an effective hole trap. An oxygen-deficient sample at 290 K provides a positive signal indicating the diffusion of holes, because the center of oxygen deficiency is an effective electron trap. This sample at 100 K provides a negative signal due to the effective self-trapping of holes.Latvian Science Council Grant No lzp-2018/1-0289; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Luminescence of α-quartz crystal and silica glass under excitation of excimer lasers ArF (193 nm), KrF (248 nm)

This work is supported by Latvian National Program “IMIS2”. We are indebted to I.I. Cheremisin for crystal samples.Luminescence of crystalline α-quartz and silica glass was studied under focused laser excitation. It was found that in crystalline α-quartz the luminescence of self-trapped exciton (STE) is excited in two-photon regime with ArF (193 nm) excimer laser. In the case of KrF (248 nm) laser excitation mainly luminescence related to near surface area is seen even without laser beam focusing. The near surface luminescence has an emission band similar to that of STE in bulk. Temperature quenching is also similar, therefore this luminescence is attributed to STE created in the area of surface. Luminescence decay kinetic of surface STE is longer than bulk STE decay (tens of ms compared to 1 ms at 80 K). Electron or/and hole self-trapping near the surface is assumed. Their recombination could provide longer duration of surface STE luminescence. Similar surface luminescence was not excited with ArF (193 nm) excimer laser. The nature of absorption for laser 248 nm photons at surface is not yet clear. Luminescence of silica glass of III type excited with focused beam of KrF (248 nm) laser resembles that of previously studied luminescence of STE in silica.IMIS2; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

ENERGY TRANSPORT IN SiO2 CRYSTALS: LUMINESCENCE EXCITATION SPECTRA OF STISHOVITE AND α-QUARTZ

The financial support of the Latvian Science Council Grant No lzp-2021/1-0215 and the funding of the University of Latvia as the Centre of Excellence within the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2, are greatly acknowledged.The migration of elementary electronic excitations was studied in a single crystal of stishovite and compared with migration in a crystal of α-quartz and polycrystalline stishovite powder. The research method is based on comparing the transfer of absorbed energy to luminescence centers, used as detectors of quasiparticles, and the near-surface nonradiative annihilation of electronic excitations. A sign of migration is the appearance of some minima in the photoluminescence (PLE) excitation spectrum in the region of maxima in the intrinsic absorption spectrum. The PLE spectrum of stishovite contains the first minimum at 9.8 eV, indicating the migration of electronic excitations and the existence of an intrinsic absorption band in stishovite at 9.8 eV. In α-quartz, the first minimum in the PLE spectrum is located at 10.5 eV and corresponds well to the intrinsic absorption band of the exciton. © 2022 Sciendo. All rights reserved.--//-- This is an open access article Trukhin A.N. ENERGY TRANSPORT IN SiO2 CRYSTALS: LUMINESCENCE EXCITATION SPECTRA OF STISHOVITE AND α-QUARTZ (2022) Latvian Journal of Physics and Technical Sciences, 59 (4), pp. 19 - 24, DOI: 10.2478/lpts-2022-0030 published under CC BY-NC-ND 4.0 licence.Latvijas Zinātnes Padome lzp-2021/1-0215; Institute of Solid-State Physics, University of Latvia has received funding from the European Union's Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.

Luminescence of localized states in oxidized and fluorinated silica glass

This work was supported by the Latvian Science Council Grant No lzp-2018/1-0289.Photoluminescence of nominally pure oxidized and fluorinated silica glasses, which have good optical transparency in the optical gap, has been investigated under excitation by excimer lasers. The data are compared with the data for chlorinated silica glass, as well as glass containing OH. The excitation of localized states provides the release and capture of charge carriers, despite the low absorption coefficient. The holes are self-trapped. The recombination in the thermally activated or tunnel process creates luminescence of oxygen-deficient centers. It is concluded that oxidation and fluorination do not change the concentration of localized states, but they change the electronic transitions of the localized states to higher energies. In type III glass with a high OH content, luminescence is suppressed by the presence of hydrogen and appears after irradiation with 7.9 eV photons of the F2 laser. This observation suggests the existence of localized states even in these glasses.Latvian Science Council Grant No lzp-2018/1-0289; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Photoluminescence and Electron Spin Resonance of ilicon Dioxide Crystal with Rutile Structure (Stishovite)

This work was supported by ERANET MYND. Also, financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/2 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The authors express our gratitude to R.I. Mashkovtsev for help in ESR signal interpretation. The authors are appreciative to T.I. Dyuzheva, L.M. Lityagina, N.A. Bendeliani for stishovite single crystals and to K. Hubner and H.-J. Fitting for stishovite powder of Barringer Meteor Crater.An electron spin resonance (ESR) and photoluminescence signal is observed in the as grown single crystal of stishovite indicating the presence of defects in the non‐irradiated sample. The photoluminescence of the as received stishovite single crystals exhibits two main bands – a blue at 3 eV and an UV at 4.75 eV. Luminescence is excited in the range of optical transparency of stishovite (below 8.75 eV) and, therefore, is ascribed to defects. A wide range of decay kinetics under a pulsed excitation is observed. For the blue band besides the exponential decay with a time constant of about 18 μs an additional ms component is revealed. For the UV band besides the fast component with a time constant of 1–3 ns a component with a decay in tens μs is obtained. The main components (18 μs and 1–3 ns) possess a typical intra‐center transition intensity thermal quenching. The effect of the additional slow component is related to the presence of OH groups and/or carbon molecular defects modifying the luminescence center. The additional slow components exhibit wave‐like thermal dependences. Photo‐thermally stimulated creation–destruction of the complex comprising host defect and interstitial modifiers explains the slow luminescence wave‐like thermal dependences.ERANET MYND; ISSP UL Nr. SJZ/2017/2 ; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART

Comparison of Luminescence in LiGaO2, Al2 O3 -Ga and Al2 O3 -Li Crystals

We have studied luminescence of LiGaO 2 , Al 2 O 3 -Ga and Al 2 O 3 -Li crystals in order to reveal the nature of luminescence centres and mechanisms in these crystals. In Al 2 O 3 -Ga presence of Ga impurities determines occurrence of the 280 nm emission band, which demonstrates intra-centre character in photoluminescence and recombination character under X-ray irradiation. In Al 2 O 3 -Li crystal lithium induced luminescence is presented with the 326 nm band, which has a recombination character. Basing on spectral similarity of the main luminescence bands in pure LiGaO 2 crystal with the dopant-induced emission bands in Al 2 O 3 , and on peculiarities of the X-ray induced thermoluminescence, the adjustment of the previous luminescence interpretation is done. It is proposed that the donor-acceptor pairs with random separation distribution responsible for the 280 nm emission are represented with gallium Ga (plus an electron) and O (plus a hole) pairs, while the donor-acceptor pairs, producing the 330 nm emission band contain a lithium ion, presumably in the interstitial position Li i , and a neighbouring oxygen ion with a caught hole.Latvian Council of Science Grant No. lzp-2018/1-0361; Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART