Financial support to this project was provided by National Research Programme (IMIS2). ; Strontium aluminate phosphors were synthesized by the solution combustion method using citric acid, urea or glycine as reducing agent and europium and dysprosium as dopants. The content of both dopants was in the range of 1-2 mol%. Dependence of phase composition, crystallite size and specific surface area on calcinations temperature, used reducing agents and dopants were determined. Luminescent properties of the calcinated at 1300 °C powders contained SrAl2O4 (90 %) and Sr4Al24O25 (10%) phases with crystallite size of 80 nm were determined. ; 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 CAMART²
Financial support provided by Scientific Research Project for Students and Young Researchers, Latvia Nr. SJZ/2018/7 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. 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 CAMART2. ; The development of nanoscale X-ray sensors is of crucial importance to achieve higher spatial resolution in many X-ray-based techniques playing a key role in materials science, healthcare, and security. Here, we demonstrate X-ray detection using individual CdS, SnO2, and ZnO nanowires (NWs). The NWs were produced via vapor–liquid–solid technique and characterized using X-ray diffraction, scanning, and transmission electron microscopy. Electrical measurements were performed under ambient conditions while exposing two-terminal NW-based devices to X-rays generated by a conventional tungsten anode X-ray tube. Fast and stable nanoampere-range X-ray beam induced current (XBIC) in response to X-ray illumination was observed. The high XBIC measured in the NW devices could be attributed to the efficient transport and collection of generated charge carriers due to the single-crystalline nature of NWs and the short NW length. Such fast-response and high-sensitivity nanoscale X-ray detectors can find applications in sub-micron resolution imaging and nanofocused beam shape measurements.--//--This is the preprint version of the following article: Edgars Butanovs, Aleksejs Zolotarjovs, Alexei Kuzmin, Boris Polyakov; Nanoscale X-ray detectors based on individual CdS, SnO and ZnO nanowires, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment: Volume 1014, 21 October 2021, 165736, which has been published in final form at https://www.sciencedirect.com/science/article/abs/pii/S016890022100721X. This article may be used for non-commercial purposes in accordance with Elsevier Terms and Conditions for Sharing and Self-Archiving. This work is licensed under a CC BY-NC-ND license. ; Scientific Research Project for Students and Young Researchers, Latvia Nr. SJZ/2018/7; 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 CAMART2.
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2017/1 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The authors are grateful to Liga Bikse for XRD measurements. ; In this study, we demonstrated for the first time the growth of ZnO nanowires (NWs) decorated with highly crystalline few-layer PbI2 and fabricated two-terminal single-nanowire photodetector devices to investigate the photoelectric properties of the hybrid nanostructures. We developed a novel two-step growth process for uniform crystalline PbI2 nanosheets via reactive magnetron deposition of a lead oxide film followed by subsequent iodination to PbI2 on a ZnO NW substrate, and we compared as-grown hybrid nanostructures with ones prepared via thermal evaporation method. ZnO–PbI2 NWs were characterized by scanning and transmission electron microscopy, X-ray diffraction analysis and photoluminescence measurements. By fabricating two-terminal single-nanowire photodetectors of the as-grown ZnO–PbI2 nanostructures, we showed that they exhibit reduced dark current and decreased photoresponse time in comparison to pure ZnO NWs and have responsivity up to 0.6 A/W. Ab initio calculations of the electronic structure of both PbI2 nanosheets and ZnO NWs have been performed, and show potential for photoelectrocatalytic hydrogen production. The obtained results show the benefits of combining layered van der Waals materials with semiconducting NWs to create novel nanostructures with enhanced properties for applications in optoelectronics or X-ray detectors. ; ISSP UL SJZ/2017/1; 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 CAMART²
Financial support provided by Scientific Research Project for Students and Young Researchers Nr. SJZ/2016/6 realized at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. Authors are grateful to Reinis Ignatans for XRD measurements. ; In recent years, nanowires have been shown to exhibit high photosensitivities, and, therefore are of interest in a variety of optoelectronic applications, for example, colour-sensitive photodetectors. In this study, we fabricated two-terminal PbS, In2S3, CdS and ZnSe single-nanowire photoresistor devices and tested applicability of these materials under the same conditions for colour-sensitive (405 nm, 532 nm and 660 nm) light detection. Nanowires were grown via atmospheric pressure chemical vapour transport method, their structure and morphology were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), and optical properties were investigated with photoluminescence (PL) measurements. Single-nanowire photoresistors were fabricated via in situ nanomanipulations inside SEM, using focused ion beam (FIB) cutting and electron-beam-assisted platinum welding; their current-voltage characteristics and photoresponse values were measured. Applicability of the tested nanowire materials for colour-sensitive light detection is discussed. ; ISSP UL Nr. SJZ/2016/6; 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 CAMART²
This work was supported by the UL ISSP grant for Scientific Research Projects for Students and Young Researchers SJZ/2016/15 . ; In this work we demonstrate a method where by adding Nb ions, Ln3+ ion luminescence intensity in HfO2 is increased for up to 15 times (in a sample containing 5 mol%Eu). The effect is described as niobium acting as a charge compensator and neutralizing the charge resulting from Ln3+ ion insertion in Hf4+ site and hence reducing the number of defects present. This is the second system where such an effect was observed, so it is expected that other metal oxides would show the same effect. The optical properties of HfO2: Eu3+ and HfO2: Eu3+, Nb5+, synthesized using the sol-gel method and annealed at various temperatures are studied. A conclusion that the structure of hafnia does not affect luminescence intensity directly and a larger role is played by factors such as defect presence and the size of the particles is drawn based on XRD and TSL measurements. Time-resolved luminescence measurements were also carried out and significant changes depending on dopant concentration and annealing temperatures were observed. Judd Ofelt theory was used to determine quantum efficiency and the local symmetry of Eu3+ ion sites. ; ISSP UL SJZ/2016/15; 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 CAMART²
The financial support of research grants ERA.NET RUS_ST20170-051 and SFERA II project "Transnational Access activities" (EU 7th Framework Programme Grant Agreement N312643). This work was partly supported by the Russian Foundation for Basic Research, project no. 18-52-76002. ; ZnO nanocrystals, undoped and doped with Iridium or Indium were prepared by solar irradiation in Heliotron reactor in PROMES CNRS facilities, France. The comparative analysis of the excitonic spectra of ZnO single crystal and ZnO nanocrystals (NCs) doped with In and Ir was performed. It is shown that the excitonic processes in Ir doped nanocrystals coincide well with electronic processes in undoped NC and single crystal; however, the electronic processes in In-doped nanocrystals are significantly different from those in single crystal. The radioluminescence spectra of ZnO:In was analysed and additional luminescence band at ∼3.18 eV was detected due to In-doping. The luminescence decay time depends on In concentration in nanocrystals and is significantly less in ZnO:In compared with undoped nanocrystals. The fast scintillation of ZnO:In makes this material promising for application. ; Russian Foundation for Basic Research 18-52-76002; Seventh Framework Programme N312643; 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 CAMART²
This research project was supported financially by ERDF Project No: Nr.1.1.1.1/16/A/182 . ; SrAl2O4:Eu,Dy is a very efficient long afterglow phosphor with wide range of possible applications. The luminescence properties and the possible luminescence mechanism of this material have been studied extensively, but there is almost no information available about the undoped material. Therefore, this article deals with the luminescence and thermally stimulated luminescence of an undoped SrAl2O4, revealing the possible defects that might be involved in the creation of the long afterglow in doped material. We conclude that undoped material exhibits some luminescence under X-ray irradiation in low temperature; close to room temperatures luminescence is almost fully thermally quenched in comparison to low temperatures. We can observe F and F2 center luminescence as well as trace metal luminescence in the emission spectrum. TSL glow curve yields the peaks that are close to those observed in material with Eu and Dy doping; therefore these peaks are clearly related to intrinsic defects. The peak at around 400 K, that is shifting with rare earth doping, might be due to dopant interaction with intrinsic defects. ; European Regional Development Fund Nr.1.1.1.1/16/A/182; 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 CAMART²
This research project was supported financially by ERDF Project No 1.1.1.1/16/A/182. ; ERDF Project No 1.1.1.1/16/A/182; 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 CAMART²
The work was supported by the ERDF funding in Estonia granted to the Center of Excellence TK141 "Advanced materials and high-technology devices for sustainable energetics, sensorics and nanoelec-tronics" (project No. 2014-2020.4.01.15-0011). Partial support of the projects from the Ministry of Education, Youth and Sports of the Czech Republic no. LO1409, LM2015088 and CZ.02.1.01/0.0/0.0/16 013/ 0001406 is also gratefully acknowledged. ; Temperature dependences of the photoluminescence and X-ray excited luminescence intensity and thermally stimulated luminescence glow curves are measured in the 4.2–300 K temperature range for the undoped and Ce3+ - doped Gd3(Ga,Al)5O12 crystals. The conclusion is made that no low-temperature quenching of the Ce3+ - related photoluminescence takes place. In both the undoped and the Ce3+ - doped crystals, temperature dependences of the X-ray excited recombination luminescence intensity correlate with the position and shape of thermally stimulated luminescence glow curve peaks of the hole origin. Low-temperature quenching of the X-ray excited luminescence in these crystals is explained by the fact that at low temperatures, free holes are trapped at oxygen ions while electrons are trapped at various intrinsic defects. In Ce3+ - doped Gd3(Ga,Al)5O12 crystals, thermally stimulated release of the trapped holes and electrons and their subsequent recombination at Ce3+ ions result in the enhancement of the Ce3+ - related electron recombination luminescence with the increasing temperature in the 10–180 K range. ; ERDF TK141 No. 2014-2020.4.01.15-0011; Ministry of Education, Youth and Sports of the Czech Republic no. LO1409, LM2015088 and CZ.02.1.01/0.0/0.0/16 013/ 0001406; 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 CAMART²
The research has been supported by the Project ERANET RUS_ST#2017-051(Latvia) and #18-52-76002 (Russia). The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework, Program H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2. ; Indium (0.038 at.%) and gallium (0.042 at.%) doped ZnO ceramics were prepared by hot pressing. Ceramics were investigated to determine their structural and mechanical characteristics for the prospective use in scintillators. Based on results of nanoindentation, atom force and scanning electron microscopy as well as energy dispersive X-ray spectra measurements, loca-tions of gallium within grain, indium at grain boundaries (GBs) and their different effect on the mechanical properties of ZnO ceramics were detected. Doping of gallium led to the increased modulus of elasticity in grain, decreased hardness near GBs, stabilization of micropores and brittle intercrystalline fracture mode. ZnO:In ceramic has modulus of elasticity and hardness values close to ZnO characteristics, the increased fracture toughness and some plasticity near GBs. Differences in the micromechanical properties of the ceramics correlate with the location of dopants. Results demonstrate that the ZnO:In ceramic has a greater stress relaxation potential than the ZnO:Ga. ---//---This work is licensed under a CC BY 4.0 license. ; Project ERANET RUS_ST#2017-051(Latvia) and #18-52-76002 (Russia); The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework, Program H2020-WIDESPREAD-01-2016-2017-Teaming Phase 2 under grant agreement No. 739508, project CAMART2.
The authors greatly acknowledge the technical and experimental support of O. Leys, M. H. H. Kolb, and R. Knitter (Karlsruhe Institute of Technology, Germany). The work is performed in the frames of the University of Latvia financed project No. Y9-B044-ZF-N-300, "Nano, Quantum Technologies, and Innovative Materials for Economics". ; Modified lithium orthosilicate (Li4SiO4) pebbles with additions of titanium dioxide (TiO2) are designed as a possible tritium breeder ceramic for the helium cooled pebble bed (HCPB) test blanket module. Additions of TiO2 were chosen to enhance mechanical properties of the tritium breeder pebbles. The formation of radiation defects (RD) in the modified Li4SiO4 pebbles with a different content of TiO2 was studied by X-ray induced luminescence (XRL) technique. After XRL measurements the accumulated RD were also analyzed by thermally stimulated luminescence (TSL) and electron spin resonance (ESR) spectrometry. XRL spectra consist of several bands with maxima at around 430, 490, 690, 700 and 800 nm. The XRL band with a peak at 490 nm could be associated with intrinsic defects in Li4SiO4 matrix whereas all the other maxima at lower photon energies are the result of the addition of TiO2. ; 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 CAMART²
The work was supported by the Institutional Research Funding IUT02-26 of the Estonian Ministry of Education and Research and the project 16-15569S of the Czech Science Foundation. ; Luminescence characteristics of Ce3+ - doped Gd3GaxAl5-xO12 single crystals with different Ga contents (x = 1, 2, 3, 4, 5) are studied in the 9–500 K temperature range. The spectra of the afterglow, photoluminescence, radioluminescence, and thermally stimulated luminescence (TSL) of each crystal coincide. The increase of the Ga content results in the high-energy shift of the spectra while the radioluminescence intensity at 9 K remains practically constant up to x = 4. No Ce3+ emission is observed in case of x = 5. The total TSL intensity drastically increases, reaches the maximum value around x = 2–3, and then decreases due to the thermal quenching of the Ce3+ emission. The TSL glow curve maxima are gradually shifting to lower temperatures, and the dependence of the maxima positions and the corresponding trap depths on the Ga content is close to linear. However, the activation energy of the TSL peaks creation under irradiation of the crystals in the 4f – 5d1 absorption band of Ce3+ decreases drastically with the increasing Ga content (especially in the range of x = 1–2), and this dependence is found to be strongly nonlinear. Possible reasons of the nonlinearity are discussed. ; Estonian Ministry of Education and Research IUT02-26; Czech Science Foundation 16-15569S; 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 CAMART²
Financial support provided by Scientific Research "Luminescence Mechanisms and Dosimeter Properties in Prospective Nitrides and Oxides Using TL and OSL Methods" LZP FLPP No. LZP-2018/1-0361 implemented at the Institute of Solid State Physics, University of Latvia is greatly acknowledged. The Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART². ; Many medical examinations involve ionizing radiation. Although the range of available dosimeters is rather wide, their linearity and chemical stability are limited. Recently, there has been a growing interest in new, improved dosimetric materials for emerging applications in medicine and other fields, such as sterilisation of consumer goods and medical instruments, irradiation of seeds, chemical agents and others.One of the classical dosimeters is carbon-doped alumina (Al2O3:C) – a well-established and widely used material for personal and industrial dosimeter with a range of great properties, such as high sensitivity, wide linearity range and relative ease of production and handling. However, the demand for reliable dosimeters in a high-dose range is still only partially fulfilled, and alumina doped with chromium ions (Al2O3:Cr) can be a promising candidate.In this study, we explored alumina doped with chromium porous microparticles synthesized with a sol-gel method as a possible high dose dosimeter and evaluated its thermostimulated luminescence signal, dose response with two irradiation sources and measured long-time fading. It was found that although the TSL signal was quite complex (consisting of two main peaks above room temperature) and the long-term fading was significant (around 50 % in the span of 30 days), with sufficient optimisation the material could be used as a high-dose dosimeter for X-ray and beta irradiation. Wide high dose linearity range, physical and chemical characteristics, as well as low production costs and ease of synthesis make chromium (III) doped alumina a compelling candidate for applicability in various medical and industry field. ---//---This work is licensed under a CC BY 4.0 license. ; LZP FLPP No. LZP-2018/1-0361; the Institute of Solid State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART².
In this study, a new approach for producing phosphorescent aluminum coatings was studied. Using the plasma electrolytic oxidation (PEO) process, a porous oxide coating was produced on the Al6082 aluminum alloy substrate. Afterwards, activated strontium aluminate (SrAl2O4: Eu2+, Dy3+) powder was filled into the cavities and pores of the PEO coating, which resulted in a surface that exhibits long-lasting luminescence. The structural and optical properties were studied using XRD, SEM, and photoluminescence measurements. It was found that the treatment time affects the morphology of the coating, which influences the amount of strontium aluminate powder that can be incorporated into the coating and the resulting afterglow intensity. ; This research project was supported financially by ERDF Project No: Nr.1.1.1.1/16/A/182; 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 CAMART²
T. G. acknowledges the ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001). K. S. and K. L. acknowledge the Latvian National Research Program IMIS2. The authors from Vinča Institute of Nuclear Sciences acknowledge the financial support of the Ministry of Education, Science and Technological Development of the Republic of Serbia (Project No: 45020 and 172056 ). ; Nanoparticles (5 nm) and nanorods (2 nm × 15 nm and 4 nm × 20 nm) of monoclinic monazite LaPO4:Eu3+ were prepared by reverse micelle and co-precipitation techniques. Effects of the particle size and surface defects on the intensity of luminescence and the emission spectrum shapes were analyzed by high resolution spectroscopy under laser (266 nm) and X-rays excitation. All synthesized LaPO4:Eu3+ samples showed similar spectral features with characteristic Eu3+ ions emission bands: 5D0→7F0 centered at 578.4 nm, magnetic-dipole transition 5D0→7F1 at 588–595 nm, electric-dipole transition 5D0→7F2 at 611.5–620.5 nm, 5D0→7F3 at (648–652 nm) and 5D0→7F4 at (684–702.5 nm), with the most dominant electric-dipole 5D0→7F2 transition. Additionally, the thermally stimulated luminescence was studied for the most dominant peak at 611.5 nm. It was shown that the Eu3+ doping creates traps in all samples. Two prominent and well resolved glow peaks at 58.7 K and 172.3 K were detected for 5 nm nanoparticles, while low-intensity glow-peaks at 212.1 K and 212.2 K were observed in the X-rays irradiated nanorods. Displayed glows could be attributed to free and bound electrons and holes or to the recombination of electrons of ionized oxygen vacancies with photogenerated holes. To obtain information about the processes and specific defect type it is necessary to carry out additional analysis for all synthesized samples. The glow curves were analyzed and trap parameters were estimated and discussed throughout the paper. ; ERDF PostDoc project No. 1.1.1.2/VIAA/1/16/215 (1.1.1.2/16/I/001); IMIS2; Ministry of Education, Science and Technological Development of the Republic of Serbia (Project No: 45020 and 172056 ); 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 CAMART²
