Wyniki wyszukiwania - Biblioteka Nauki

1

Structural and Optical Properties of ZnO and Co Doped ZnO Thin Films Prepared by Sol-Gel

100%

Khantoul A. , Sebais M. , Rahal B. , Boudine B. , Halimi O.

Acta Physica Polonica A

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2018

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tom 133

|

nr 1

114-117

EN

We report on ZnO films doped with different Co concentrations (0, 0.5, and 1 wt%) prepared by sol-gel technique in association with dip-coating onto glass substrates. Zinc acetate dehydrate, cobalt acetate, mono ethanolamine were used as starting materials, as well as solvent and stabilizer, respectively. Nanostructured polycrystalline ZnO thin films with different concentrations of Co doping (0, 0.5, and 1 wt%) are prepared for the first time by the sol-gel method and annealed at 500°C for 1 h. The surface morphologies of the ZnO thin films deposited on glass substrate with different concentrations were evaluated by atomic force microscopy. The optical absorption of the films showed a blue shift of the band gap. The photoluminescence signal of the thin films of undoped and Co-doped ZnO presents different bands in the visible region. The electrical conductivity of the sample with 0.5%Co was found to be 4.62 (ΩCm)¯¹.

2

Novel soluble aromatic poly(amideimide)s containing 9,9-diphenylfluorene moieties: characterization and optical properties

100%

Schab-Balcerzak E. , Grabiec E. , Jarząbek B. , Grobelny Ł. , Kurcok M. , Mazurak Z.

Open Chemistry

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2006

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tom 4

|

nr 4

604-619

EN

A series of aromatic poly(amideimide)s containing 9,9-diphenylfluorene moieties and the amide units in the main chain have been synthesized by solution polycondensation reaction of newly prepared diamidedianhydride with several aromatic diamines: 1,3-phenylenediamine, 3,3′-dimethoxy-biphenyl-4,4′-diamine, 4,4′-oxydianiline, 4,4′-(1,3-phenylenedioxy)dianiline, 4,4′-(9-fluorenylidene)dianiline and 1,5-diaminonaphthalene. Molecular structures of the polymers obtained have been characterized using 13C NMR, 1H NMR and FTIR spectroscopies. The polymers prepared are readily soluble in aprotic polar solvents, and form optically transparent films by solution casting. The resultant poly(amideimide)s have been analyzed by differential scanning calorimetry (DSC), thermogravimetry (TG) and wide-angle X-ray diffraction measurements. They exhibited high levels of thermal stability, with decomposition temperatures in the range 452–494 °C, and high glass transition temperatures (181–278 °C). The optical behavior of these polymers has been investigated in NMP solution as well as in the films. The photoluminescence (PL) spectra of the free-standing films prepared from the poly(amideimide)s exhibited maximum emission bands around 506–525 nm in the green region.

3

Optical and electrical characterization of defects in zinc oxide thin films grown by atomic layer deposition

100%

Krajewski T. A. , Łuka G. , Wachnicki Ł. , Jakieła R. , Witkowski B. , Guziewicz E. , Godlewski M. , Huby N. , Tallarida G.

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2009

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tom Vol. 39, nr 4

865-874

EN

In the present paper, we discuss the influence of point defects on electrical and optical characteristics of ZnO thin films grown by the atomic layer deposition (ALD) method. The films were grown on glass substrates at low temperature (100-200 °C). We used diethylzinc (DEZn) and deionized water as precursors. Room temperature photoluminescence (RT PL) spectra, secondary ion mass spectroscopy (SIMS), electron dispersive X-ray (EDX) analysis and Hall effect measurements were made for as-grown ZnO layers and for the annealed ones (in air at 300 and 400 °C as well as in N2 atmosphere at 400 °C). The air-annealed ZnO films reveal a substantial reduction of a carrier concentration (up to 4 orders of magnitude - from 1019 to 1015 cm-3) combined with changes in intensity of the defect-related luminescence bands. PL related to deep defects is shifted towards the lower energy range (red light emission) after annealing (in air and nitrogen-rich conditions).

4

Luminescent homo- and hetero-metallic hybrid molecular materials constructed by covalent grafting

100%

Wang F. F. , Yan B.

Materials Science Poland

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2013

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tom Vol. 31, No. 1

108-114

EN

In this paper, 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPIC) was modified by ethylparaben (EPB) to produce corresponding organic-inorganic monomers (EPB-TESPIC) with two components equipped with covalent bonds, which not only can coordinate to RE ions (Tb3+ and Eu3+) but also act as a sol-gel precursor. Luminescent hybrid materials consisting of terbium-europium complex, covalently bonded to silica-based network, have been obtained in situ via a sol-gel approach. Proton nuclear magnetic resonance spectroscopy (1HNMR) and Fourier transform infrared spectroscopy (FT-IR) were applied to characterize the structure of EPB-TESPIC. UV-visible, phosphorescence, and luminescence spectra were obtained to characterize the photophysical properties of the obtained hybrid material. Through co-hydrolysis and polycondensation, Tb3+ and Eu3+ can be introduced into the same organic-inorganic hybrid monomer, forming Si-O backbones. The experimental results show that the strong luminescence of rare-earth ions substantiates the optimum energy match and effective intramolecular energy transfer between the triplet state energy of coordination complex and the emissive energy level of the rare-earth ions. The hybrid material systems are expected to have potential applications in photophysical sensors.

5

Photoluminescence of gamma-, proton- and alpha-irradiated LiF detectors

100%

Marczewska B. , Bilski P. , Mandowska E. , Mandowski A.

Open Physics

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2012

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tom 10

|

nr 4

1009-1012

EN

Lithium fluoride (LiF), one of the most pervasive alkali halides in optical device research, is routinely used in optical data storage and radiation protection. LiF crystals may contain different aggregate defects produced by several types of ionizing radiation, with the number of defects being proportional to the cumulative radiation dose. Stimulation of irradiated LiF detectors by heating or with blue light causes thermoluminescence (TL) or photoluminescence (PL), respectively. We developed a new PL reader equipped with a blue light-emitting diode for stimulation and a Hamamatsu photomultiplier for registering green emissions, dedicated to examining LiF detectors as well as more broadly investigating TL/PL emission from standard LiF detectors irradiated with gamma rays, 60 MeV protons and alpha particles. The results confirmed very high efficiency PL signal from alpha-irradiated LiF detectors corresponding to their low efficiency after gamma irradiation, and vice versa for TL readout. Combining the TL and PL readouts permits us to discriminate between how different kinds of radiation affect efficiency in LiF detectors.

6

Luminescent properties and the morphology of SrMoO4:Eu3+ powders synthesized via combining sol-gel and solid-state route

100%

Wei Q. , Chen D.

Open Physics

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2010

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tom 8

|

nr 5

766-770

EN

SrMoO4:Eu3+ red phosphors were prepared by combining sol-gel and solid-state route. Citric acid and ethylenediaminetetraacetic acid (EDTA), employed as the chelating agents, were added to the aqueous solutions of metal nitrates. X-ray diffraction (XRD) and photoluminescent spectra techniques (PL) were used to characterize the resultant powders. The results indicated the obtained SrMoO4:Eu3+ phosphors were fine powders with a particle size of 50 nm. The effects of synthesizing conditions were also investigated and optimized, which included the synthesis temperature and the activator concentration on the luminescent intensity. Compared with SrMoO4:Eu3+ phosphors prepared by Solid-state reaction SrMoO4:Eu3+ phosphors prepared by combining sol-gel and solid-state route showed appropriate particle size and a higher emission intensity.

7

Photoluminescence spectroscopy for the evaluation of band potential roughness of InGaN active layers

100%

Kazlauskas K. , Jursenas S. , Miasojedovas S. , Pobedinskas P. , Tamulaitis G. , Zukauskas A. , Ivanov V. Y. , Godlewski M.

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2006

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tom Vol. 36, nr 2-3

181-185

EN

Photoluminescence spectroscopy in combination with Monte Carlo simulation of exciton hopping is demonstrated to be a valuable tool for quantitative analysis of the band potential profile in active layers for InGaN-based light emitters. Recently proposed double-scaled potential profile model is used to reveal the scale of potential fluctuations in the individual In-rich regions as well as the dispersion of the average exciton localization energy in these regions. The influence of the different potential fluctuation scales on the stimulated emission threshold and luminescence decay time of highly excited InGaN active layers is studied.

8

Photoluminescence of bis(8-hydroxyquinoline) zinc (Znq2) and magnesium (Mgq2)

100%

Tsuboi T. , Nakai Y. , Torii Y.

Open Physics

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2012

|

tom 10

|

nr 2

524-528

EN

Absorption and photoluminescence (PL) spectra, PL quantum efficiency, and PL lifetime have been investigated on bis(8-hydroxyquinoline) zinc (Znq2) and magnesium (Mgq2) in solutions and powder. Znq2 and Mgq2 have the lowest-energy absorption band at 376 and 396 nm in acetonitrile solution, respectively, and emission band with peak at 555 and 480 nm. The PL quantum efficiency is 0.03 and 0.45 for Znq2 and Mgq2 in the solution, respectively, while 0.45 and 0.36 in powder. Unlike the case of powders, two PL lifetimes are obtained in solutions. The longer lifetime is attributed to molecule having interaction with its neighboring molecule, while the shorter one to the isolated single molecule.

9

The photoluminescent properties of CdS clusters of different size in porous glasses

100%

Rysiakiewicz-Pasek E. , Polańska J. , Gevelyuk S. A. , Doycho I. K. , Mak V. T. , Zhukov S. A.

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2008

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tom Vol. 38, nr 1

93-100

EN

CdS nanoclusters were formed in the porous glass matrix by sequential chemical deposition from liquid-vapor phase and their chemical content was investigated. The room temperature photoluminescence spectra of specimens excited with a 235 nm wavelength had typical narrow peaks at 400 nm. The peaks can be explained by quantum effects for charge carriers confined inside the small-size (radius of the order of several nanometers) clusters. At the same time the luminescence spectra of the same specimens, but excited with a xenon lamp at 77 K, had peaks at ~700 nm that approximately corresponded to the band gap of the crystalline CdS. The possibility of the crystallites existence follows from the size distribution of voids in the porous glass matrix and is confirmed by the X-ray spectra typical of the wurtzite structure. The peculiarities of the observed luminescence spectra are explained by the energetic diagram of CdS in the configurational space.

10

Luminescence based on energy transfer in xerogels doped with Tb2-xEux(WO4)3

100%

Grobelna B.

|

2008

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tom Vol. 38, nr 1

39-47

EN

A series of luminescent materials consisting of Tb2-xEux (WO4)3 entrapped in silica xerogel were successfully prepared. The parameter x in the formula changed from 0.4 to 2. Spectroscopic properties such as absorption and luminescence of optically active ions were studied at room temperature. Owing to the energy transfer from the WO42- groups (ligand-metal charge transfer, (LMCT)) the lanthanide ions show their characteristic emissions in Tb2-xEux(WO4)3 entrapped in silica xerogel, i.e., 5D0 › 7FJ (J = 0, 1, 2, 3, 4) transition for Eu3+ ion and 5D4 › 7FJ (J = 6, 5, 4, 3) transition for Tb3+ ion. The energy transfer is effective for the mixed tungstate salt Tb1.35Eu0.65(WO4)3 entrapped in silica xerogel. The Eu(III) emission intensity in the materials under study increases with an increase in the annealing temperature from 600 to 900 °C. This is due to the removal of the effective O -H quenchers from the coordination sphere of the Eu(III) ion.

11

Influence of terbium on structure and luminescence of nanocrystalline TiO2 thin films

88%

Wojcieszak D. , Kaczmarek D. , Domaradzki J. , Lukowiak A. , Strek W.

Open Physics

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2013

|

tom 11

|

nr 2

239-244

EN

In this work analysis of the structural and optical properties of TiO2 thin films doped with terbium has been described. Samples were prepared by a high energy reactive magnetron sputtering process under low pressure of oxygen plasma. X-ray diffraction results have shown that different TiO2 crystal forms have been produced, depending on the amount of Tb dopant. The undoped matrix had rutile structure with crystallites with a size of 8.7 nm, while incorporation of 0.4 at. % of Tb into the film during the sputtering process resulted in anatase structure with bigger crystallites (11.7 nm). Increasing the amount of terbium up to 2 at. % and 2.6 at. % gave rutile structure with crystallites with a size of 6.6 nm for both films. However, Raman spectroscopy has revealed that in the case of TiO2:(2 at. % Tb), except for the rutile form, the presence of fine-crystalline anatase was observed. Moreover, the lack of Raman peaks shift attests to the lack of stress in the titania lattice of all of the TiO2:Tb films. This fact indicates localization of Tb3+ ions on the surface of TiO2 nanocrystals. In the case of optical investigation, results have shown that doping with terbium has a significant influence on the properties of TiO2, but it does not decrease the high transparency of the matrix. The observed changes of the transmission characteristics were produced only due to modification of the TiO2:Tb structure. Photoluminescence measurements have shown that emission of light from TiO2:Tb films occurs when the amount of terbium is 2.6 at. %. Based on the obtained results a scheme of direct energy transfer from titanium dioxide matrix (with rutile structure) to Tb3+ ions has been proposed.

12

Influence of microwave plasma parameters on light emission from SiV color centers in nanocrystalline diamond films

88%

Himics L. , Tóth S. , Veres M. , Csíkvári P. , Koós M.

Open Chemistry

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2015

|

tom 13

|

nr 1

EN

Zero phonon line (ZPL) shape, position and integral intensity of SiV defect center in diamond is presented for nanocrystalline diamond (NCD) films grown at different conditions, NCD films of average grain sizes from ~50 nm up to ~180 nm have been deposited onto c-Si wafer at substrate temperature of 700 and 850oC from mixture with different CH4 and H2 ratios using MWCVD process. Light emission of SiV defect center and Raman scattering properties of NCD samples were measured on a Renishaw micro-Raman spectrometer with 488 nm excitation. Scanning electron microscopy images were used for monitoring surface morphology and for the analysis of the average grain sizes. Sample thickness was determined by in situ laser reflection interferometry. Characteristics of SiV ZPL are discussed in light of the morphology, bonding structure and average grain size of NCD films.

13

Afterglow and thermoluminescence of ZrO2 nanopowders

88%

Puust L. , Kiisk V. , Utt K. , Mändar H. , Sildos I.

Open Physics

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2014

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tom 12

|

nr 6

415-420

EN

A careful study of the phosphorescence afterglow and the thermoluminescence (TL) of sol-gel-prepared m-ZrO2 nanocrystalline powders in an extended temperature range −100 to 300 °C was carried out. Wavelength-resolved TL proved the existence of a single active luminescence centre in this temperature range. A TL method based on various heating rates was used to derive more reliable trap depths of 0.75, 0.95, 1.25, 1.46 and 1.66 eV whereas deconvolution methods provided somewhat lower values. The most intense room-temperature afterglows (that were easily observable beyond 1000 s) were obtained from samples annealed at 1250 and 1500 °C, and were attributed mainly to depopulation of the 1.25 eV traps.

14

White and Saturated Blue Phosphorescent OLED based on the Non-Emissive Homoleptic Complex Ir(ppz)3as single active material

88%

Lepeltier M. , Dumur F. , Wantz G. , Bertin D. , Gigmes D. , Mayer C. R.

Optical Data Processing and Storage

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2014

|

tom 1

|

nr 1

EN

The well-known homoleptic iridium (III) complex Ir(ppz)3 which is only emissive in solution at low temperature has been investigated as dopant in a p − i stacked OLED architecture. Interestingly, while using this phosphor as a single emitter, awhite OLED was obtained. Emission colour was determined as being concentration and thickness-dependent.

15

Spectroscopic properties of the Pr3+ ion in TeO2-WO3-PbO-La2O3 and TeO2-WO3-PbO-Lu2O3 glasses

88%

Burtan B. , Sitarz M. , Lisiecki R. , Ryba-Romanowski W. , Jeleń P. , Cisowski J. , Reben M.

Open Physics

|

2014

|

tom 12

|

nr 1

57-62

EN

The goal of this work was to investigate the spectroscopic properties of Pr3+ ions, embedded in two different tellurite glass matrices, TeO2-WO3-PbO-La2O3 and TeO2-WO3-PbO-Lu2O3. The absorption and fluorescence spectra have been recorded and analyzed in terms of the Judd-Ofelt theory along with the luminescence decay of the 3P0 and 1D2 levels of the Pr3+ ion. The spectroscopic studies were completed with ellipsometric measurements providing the dispersion relation of the refractive index of the investigated glasses.

16

Influence of the second shell layer (TOPO, HDA) on the optical properties of CdSe/ZnS nanocrystal powder

88%

Zatryb G. , Podhorodecki A. , Misiewicz J. , Nauka K.

|

2007

|

tom Vol. 37, nr 4

459-464

EN

CdSe/ZnS nanocrystal powder covered with an additional cap layer (II-shell) of hexadecylamine (HDA) or tri-n-octylphosphine oxide (TOPO) has been investigated by using photoluminescence (PL) and total photoluminescence excitation (TPLE) spectroscopy. Depending on II-shell composition, different emission properties of the system have been observed. Strong emission bands at 2.00 eV and 1.95 eV related to nanocrystalline CdSe core recombination have been observed for TOPO and HDA-CdSe/ZnS nanocrystals, respectively. In both cases, weak emission bands centered at 3.5 and 2.8 eV have also been found. Moreover, in the case of TOPO II-shell, emission band at 1.65 eV related to defect state recombination has been observed. In both cases, similar absorption properties have been found, indicating that II-shell composition does not change nanocrystal absorption properties in an efficient way.

17

The birefringence spectroscopic studies on ferroelectric glycine phosphite (GPI) single crystals

88%

Bhoopathi G. , Jayaramakrishnan V. , Ravikumar K. , Prasanyaa T. , Karthikeyan S.

Materials Science Poland

|

2013

|

tom Vol. 31, No. 1

1-5

EN

The ferroelectric glycine phosphite single crystals have been grown from aqueous solution by both conventional and Sankaranarayanan-Ramasamy methods. The modified channelled spectrum method has been adopted for spectral dependence of optical birefringence studies over the wavelength range of 480-620 nm, which show that both the crystals exhibit relatively high birefringence values. The photoluminescence excitation studies were carried out for the grown crystals in a wide wavelength range between 300 nm and 600 nm at 224 K. The crystals were also subjected to scanning electron microscopy analysis in order to determine the ferroelectric domain pattern configuration.

18

Growth, optical and EPR properties of Li1.72Na0.28Ge4O9 single crystals pure and slightly doped with Cr

88%

Jasik A. , Berkowski M. , Kaczmarek S. , Suchocki A. , Kaminska A. , Leniec G. , Nowakowski P. , Domukhovski V.

Open Physics

|

2012

|

tom 10

|

nr 2

506-513

EN

Single crystals of lithium-sodium-tetragermanate, a member of the solid solution series Li2−xNaxGe4O9 with x=0.28, pure and slightly doped with Cr3+ ions (0.03 mol.% and 0.1 mol.%), were grown in ambient atmosphere by the Czochralski technique from stoichiometric melt. The crystals with dimensions up to 20 mm in diameter and 50 mm in length were obtained. The crystal structure has been determined by means of X-ray diffraction. Phase analysis and structural refinement of the Li1.72Na0.28Ge4O9 crystals were performed by X-ray powder diffraction using Ni-filtered Cu Kα radiation with a Siemens D5000 diffractometer. The absorption, excitation and photoluminescence spectra of the crystals were measured in the UV-VIS and IR range at low temperatures. EPR investigations were performed using a conventional X-band Bruker ELEXSYS E 500 CW-spectrometer operating at 9.5 GHz with 100 kHz magnetic field modulation. Temperature and angular dependences of the EPR spectra of the crystal samples were recorded in the 3–300 K temperature range.

19

Influence of Polarization Processes on the Morphology and Photoluminescence Properties of PP/TiO₂ Polymer Nanocomposites

88%

Ramazanov M. , Hajiyeva F. , Maharramov A. , Hasanova U. , Ahmadova A. , Rahimli A. , Shirinova H.

Acta Physica Polonica A

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2017

|

tom 131

|

nr 6

1540-1543

EN

The paper reports of synthesis and investigation of polymeric nanocomposites based on isotactic polypropylene and titanium dioxide nanoparticles PP+TiO₂ (PPT). The structure of the PPT nanocomposites was studied by scanning electron and atomic force microscopy. There was also studied the influence of the polarization process by corona discharge on the structure and photoluminescence properties of PPT nanocomposites. It was found that intensity of the photoluminescence after the polarization increases, and this depends on the concentration of titan dioxide nanoparticles in the polymer matrix. It was shown that rms roughness for non-polarized sample compositions is 60-100 nm, whereas for polarized samples after the corona discharge polarization, makes 20-40 nm, i.e. there takes place grinding of the structural elements. It is supposed that, in the composite there forms sufficiently high internal local field, due to the boundary charges, so under the influence of this field there were excited additional luminescent centers, and as a result, after the polarization there was observed the increase of luminescence intensity.

20

Optical and microstructural properties of self-assembled InAs quantum structures in silicon

88%

Prucnal S. , Turek M. , Drozdziel A. , Pyszniak K. , Wójtowicz A. , Zhou S.-Q. , Kanjilal A. , Shalimov A. , Skorupa W. , Zuk J.

Open Physics

|

2011

|

tom 9

|

nr 2

338-343

EN

The InAs quantum structures were formed in silicon by sequential ion implantation and subsequent thermal annealing. Two kinds of crystalline InAs nanostructures were successfully synthesized: nanodots (NDs) and nanopyramids (NPs). The peaks at 215 and 235 cm−1, corresponding to the transverse optical (TO) and longitudinal optical (LO) InAs single-phonon modes, respectively, are clearly visible in the Raman spectra. Moreover, the PL band at around 1.3 µm, due to light emission from InAs NDs with an average diameter 7±2 nm, was observed. The InAs NPs were found only in samples annealed for 20 ms at temperatures ranging from 1000 up to 1200°C. The crystallinity and pyramidal shape of InAs quantum structures were confirmed by HRTEM and XRD techniques. The average size of the NPs is 50 nm base and 50 nm height, and they are oriented parallel to the Si (001) planes. The lattice parameter of the NPs increases from 6.051 to 6.055 Å with the annealing temperature increasing from 1100 to 1200°C, due to lattice relaxation. Energy dispersive spectroscopy (EDS) shows almost stoichiometric composition of the InAs NPs.