Wyniki wyszukiwania - Biblioteka Nauki

1

Reflectivity spectra of some conducting BETS salts

100%

Kaplunov M. G. , Kushch N. D. , Krasnikova S. S.

|

tom Vol. 22, No. 4

359--364

EN

We have measured the polarized reflectivity spectra of three BETS-based organic metals with the a-phase structure: a-(BETS)2NH4Hg(SCN)4 (I), a-(BETS)2TlHg(SeCN)4 (II), and a-(BETS)2Cu5I6 (III) in the range of 600-6500 cm-1. The spectra exhibit a metallic-type reflection with the plasma edge about 4000-5000 cm-1 and high reflectivity at low frequencies. The electron-vibrational bands observed in the range of 1200-1400 cm-1 are due to the interaction of the intramolecular vibrational modes of BETS with conduction electrons.

2

First-principles calculations to investigate structural, electronic and optical properties of (AlSb)m/(GaSb)n superlattices

80%

Caid M. , Rached D.

|

tom Vol. 38, No. 2

320--327

EN

The structural, electronic and optical properties of (AlSb)m/(GaSb)n (m-n: 1-1, 2-2, 1-3 and 3-1) superlattices are investigated within the density functional theory (DFT) by using the last version of the first principles full potential linear muffin tin orbital method (FP-LMTO) as implemented in LmtART 7.0 code. The exchange and correlation potential is treated by the local density approximation (LDA) for the total energy calculations. Our calculations of the band structure show that the superlattices (n ≠ 1) have a direct band gap Γ-Γ. The optical constants, including the dielectric function ϵ(w), the refractive index n(w) and the reflectivity R(w) are calculated and discussed.

3

Structural and optical properties of nanostructured bismuth oxide

80%

Ali R. S.

International Letters of Chemistry, Physics and Astronomy

|

2014

|

tom Vol. 15

64--72

EN

Thin films of bismuth oxide have been prepared utilizing vacuum evaporation. XRD anyalysis reveal that all the films were tetragonal polycrystalline structure with a preferred orientation along (002) plane. SEM images indicate that the grain size fall in the category of nanosize. AFM results assure that the nanonstructure behavior of thin films. Optical studies show that these films have a direct transition with optical energy gap equal to 2.5 eV.

4

Zinc Oxide nanoparticles synthesis by use of aqueous extracts of Muntingia calabura L.

80%

Manokari M. , Shekhawat M. S.

|

tom 22

31-40

EN

Biological synthesis of metal nanoparticles gained worldwide interest due to their rapid, non-toxic, economical, single-step technique and eco-friendly alternative. Green-chemical approach of production of Zinc Oxide (ZnO) nanoparticles (NPs) has been exploited in the field of medicine, food packaging, nano-optical and electrical devices. Muntingia calabura is a multipotent medicinal plant with astounded biological activities and phytoconstituents. The nanoparticles obtained using aqueous extracts of various parts of M. calabura were characterized with UV-VIS spectroscopy to obtain information concerning the optical properties of synthesized ZnO nanoparticles. The proposed green and economical method could be used for large scale production of nanostructures because of its advantages over other physical and chemical methods.

5

Effect of annealing temperature on the optical properties of ZnO nanoparticles

80%

Ismail R. A. , Habubi N. F. , Abid H. R.

|

tom Vol. 4

37--47

EN

In this work, ZnO films were prepared by drop casting technique. The films were deposited on quartz substrates under different annealing time (15,30,45 and 60 min.) at a constant temperature (800 °C). The optical properties were achieved by measuring the absorbance and transmittance spectra in the wavelength range (200-900) nm. It was found that the absorbance decreases while transmission increases as the annealing time increases, while the reflectance decreases as the annealing time increases. The optical measurements indicate the kind of transition which was a direct allowed with an average band gap energies lie between 3.3 eV and 3.54 eV with the change of annealing time.

6

Electrical and optical properties of new Pr3+-doped PbWO4 ceramics

80%

Groń T. , Piątkowska M. , Tomaszewicz E. , Sawicki B. , Urbanowicz P. , Duda H.

|

tom Vol. 36, No. 4

530--536

EN

Polycrystalline samples of new scheelite-type tungstates, Pb1−3x xPr2xWO4 with 0.0098 ⩽ x ⩽ 0.20, where denotes cationic vacancies have been successfully prepared by a high-temperature solid-state reaction method using Pr2 (WO4)3 and PbWO4 as the starting reactants. The influence of the Pr3+ substitution in the scheelite framework on the structure and optical properties of prepared new ceramic materials has been examined using powder X-ray diffraction method (XRD) and UV-Vis-NIR spectroscopy. The results of dielectric studies of Pb1−3x xPr2xWO4 samples showed both low values of dielectric constant (below 14) and loss tangent (below 0.2). The electrical conductivity and thermoelectric power measurements revealed a low conductivity (∼2 × 10−9 S/m) and the sign change of thermoelectric power around the temperature of 366 K suggesting the p-n transition. These results are discussed in the context of vacancy, acceptor and donor levels as well as the Maxwell-Wagner model.

7

Direct formation of ZnO nanorods by hydrothermal process: study on its optical properties and electron transport

80%

Mufti N. , Fuad A. , Fibriyanti A. A. , Maryam S. , Kurniawan R. , Taufiq A. , Sunaryono , Rusydi A.

|

tom Vol. 38, No. 1

91--96

EN

We report a new direct fabrication of the ZnO nanorods (NR) by hydrothermal method, in which the preparation of seed layer is eliminated. We show that the tuning of initial temperature rate during the hydrothermal process plays a key role in the structural modification of the ZnO NR. A highly oriented ZnO NR is successfully fabricated by using a low rate of initial temperature. The increase of optical absorption and electron transport was obtained by reducing the diameter and increasing distribution of the ZnO NR on the substrate. Interestingly, an additional absorption from the defects is obtained in the system, which plays an important role in expanding the optical absorption. Our system will provide a favourable characteristic for developing the high-performance optoelectronic devices with high optical absorption and high electron transport.

8

High pressure spectroscopy of Pr3+ doped KLa(MoO4)2 crystal

80%

Galanciak D. , Gryk W. , Grinberg M. , Macalik L. , Mączka M.

|

2006

|

tom Vol. 36, nr 4

s. 443--450

EN

Optical properties and electronic structure of Pr3+ ion in KLa0.75Pr0.25(MoO4)2 have been investigated. The standard spectroscopy (excitation and photoluminescence spectra) and the high pressure spectroscopy methods have been used. Hydrostatic pressure up to 100 kbar has been applied in diamond anvil cell. The luminescence related to the transitions from the 3P0 and 1D2 states have been measured at ambient temperature for different pressures. We have found that the pressure shifts of the observed emission lines are negative and equal to 2–3 cm–1/kbar. It is due to the changes in Slater and α, β, γ parameters and diminishing of the spin-orbit coupling constant ζ.

9

Under Pressure DFT Investigations on Optical and Electronic Properties of PbZrO₃

80%

Nazir G. , Tariq S. , Afaq A. , Mahmood Q. , Saad S. , Mahmood A. , Tariq S.

|

tom 133

|

nr 1

105-113

EN

In this article, density functional theory has been used to investigate the structural and optoelectronic properties of PbZrO₃ (PZO) under pressure from 0 to 350 GPa. In order to achieve ground state structural stability, generalized gradient approximations has been utilized. By studying electronic properties, indirect band-gap nature of PZO appears to change at 15 GPa to direct band-gap. Optical analysis include under pressure responses of real and imaginary parts of dielectric function, optical conductivity, optical absorption coefficient, energy loss function, refractive index, reflectivity and extinction coefficient. Most of the results have been found to be consistent with literature. Study reveals that static dielectric constant and band-gap are in accordance with the Penn model which validates our computed results. Moreover, static dielectric constant and static refractive index directly increases with pressure. Material preserves its positive value of refractive index at all pressures and therefore, it is not a negative index metamaterial. Plasma frequency increases directly with pressure that destabilize the under study material. Our results could be very useful for developing novel optoelectronic devices based on PZO suitable to work under extreme conditions.

10

Luminescence properties of Eu3+-doped Al2(WO4)3

80%

Macalik L. , Hanuza J. , Hermanowicz K. , Godlewska P. , Sidorov N. V.

|

tom Vol. 22, No. 2

145--152

EN

Emission spectra of Al2(WO4)3 doped with Eu3+ were recorded at room temperature (orthorhombic phase) and at 10 K (monoclinic phase). The luminescence excitation spectra and luminescence decay profiles were recorded for both structural modifications at RT and LN2T, and the luminescence lifetimes of Eu3+ have been estimated. Two-site behaviour of the optically active ions in both phases has been revealed in the luminescence studies. However, the emission decay profiles give one lifetime of the 5D2 level, equal to 1.8 ms and 848.4 žs at room temperature and liquid nitrogen temperature, respectively. The results obtained have been explained in terms of an unusual location of Eu3+ ions inside the crystal tunnels, parallel to the c-axis.

11

Some new findings in t-phase organic conductors

80%

Papavassiliou G. C. , Mousdis G. A. , Anyfantis G. C. , Murata K. , Nakanishi T. , Li L. , Yoshino H. , Tajima H. , Inoue M. , Konoike T. , Brooks J. S. , Chor E. S. , Graf D.

|

tom Vol. 22, No. 4

365--372

EN

Some new findings concerning the structural, optical, transport, and magnetotransport properties of t-phase organic conductors, based on the donor molecules ethylenedioxy-S,S-dimethylethylenedithiotetrathiafulvalene, ethylenedioxy-R,R-dimethylethylenedithio-tetrathiafulvalene, pyrazino-S,S-dimethylethylenedithio- tetrathiafulvalene, pyrazino-R,R-dimethylethylenedithio-tetrathiafulvalene, pyrazino-r-dimethylethylenedithio- tetrathiafulvalene, pyrazino-S,S-dimethylethyledithio-diselenadithiafulvalene, pyrazino- r-methylethylenedithio-tetrathiafulvalene, and pyrazino-r-methylethylenediseleno-tetrathiafulvalene are described. Some similarities and differences in their properties are discussed.

12

Nonlinear dependence of optical gap of a-Si₁-xGex:H films on Ge content (x<0.4)

80%

Dimova-Malinovska D.

Opto-Electronics Review

|

2000

|

tom Vol. 8, No. 4

382-384

EN

The dependence of optical band gap of a-Si₁-xGex:H films on Ge content is discussed. The films are deposited by magnetron co-sputtering of c-Si target with c-Ge chips on it in Ar + H₂ atmosphere. It has been observed that concentration of the bondeh hydrogen decreases with Ge content in the films. The results of study show that variation of the optical band gap of a-Si₁-xGex:H films on Ge concentration follows the nonlinear law. This is related to the nonlinear changes of H concentration in the films.

13

Saturation in the principal (excited) channel of four-level medium as an effective two-level configuration

80%

Addasi J. S.

Optica Applicata

|

2021

|

tom Vol. 51, nr 2

235--244

EN

Saturation of complex molecules affects the nonlinear processes occurring in the medium. The medium can be described by two-, three-, and four-level configurations. The principal singlet-singlet and excited triplet-triplet channels of a four-level, N-type, configuration were used to study a nonlinear medium, which was excited by radiation with two frequencies. Under weak population of energy levels in the triplet-triplet channel (a small ratio of the total probability of spontaneous and irradiate transitions for both channels p23/p31), the principal (singlet-singlet) channel is similar to a two-level configuration. At the same time, the effective population of the energy levels in the triplet-triplet channel (the ratio p23/p31 is large and the radiation intensity in the principal channel is high) makes the excited (triplet-triplet) channel coincide with the two-level configuration. The saturation intensity of radiation in principal (excited) channel, as effective two-level configuration, and nonlinear processes in this channel can be controlled by external radiation acting on excited (principal) channel. Finally, the average excitation of molecules into the energy levels in the triplet-triplet channel (ratio p23/p31 ≈ 1) makes the four-level configuration similar to the three-level configuration with effective level as a result of combination between second singlet level S2 and first triplet level T1.

14

EPR and optical properties of Li₂B₄O₇:Mn glass samples under the influence of y-irradiation and annealing

80%

Podgórska D. , Kaczmarek S. M. , Włodarski M. , Kwaśny M. , Warchoł S. , Rizak V. M. , Drozdowski W. , Berkowski M.

|

tom Vol. 54, nr 1

45-59

EN

Li₂B₄O₇ glasses doped with Mn²⁺ (0.1 mol. %), have been investigated using electron paramagnetic resonance (EPR) method at 9.4 GHz. Mn ion is found enter substantially for the Li⁺ ion as Mn²⁺ and/or Mn¹⁺, and, probably for the B³⁺ ion or interstitial as Mn³⁺. In consequence at least two types of the manganese ions arise in the EPR spectrum in the same range of magnetic field. The EPR spectrum of glass system exhibits three resonance signals, at g ≈ 2.00, g ≈ 2.68 and g ≈ 4.60 and is very similar to others reported for Mn²⁺ ions glass systems. Only 620 nm emission was observed in the photoluminescence spectrum of the "as-grown" glass, while 430 nm and 610 nm emissions in radiolu-minescence spectrum of the system. Four month after ɣ-irradiation we observed three emission peaks centered at 430, 540 and 620 nm. The 430 nm emission was excited with 225, 277 and 374 nm absorption, the 540 nm emission was excited with 225 and 411 nm absorptions, and the 620 nm emission was excited with 225, 360, 411 and 550 nm absorptions.

PL

Badano szkła Li₂B₄O₇ domieszkowane Mn (0,1 mol %) wykorzystując metodę elektronowego rezonansu paramagnetycznego dla częstotliwości 9,4 GHz. Stwierdzono, że jon Mn podstawia się w położenie jonu Li⁺ jako Mn²⁺ oraz/lub jako Mn¹⁺, a także prawdopodobnie w położenie jonu B³⁺ jako Mn³⁺. W konsekwencji, co najmniej dwa rodzaje jonów Mn reprezentowane są w widmie EPR. Widmo EPR szkła LBO domieszkowanego Mn wykazuje obecność trzech sygnałów rezonansowych, dla g ≈ 2,00, g ≈ 2,68 oraz g ≈ 4,60. W przypadku szkła LBO:Mn badanego tuż po wzroście, w widmie fotoluminescencji stwierdzono obecność emisji z maksimum dla 620 nm, zaś w widmie radioluminescencji emisji 430 nm i 610 nm. Naświetlenie tego szkła kwantami gamma przesuwa widmo emisji w stronę fal długich obniżając jego intensywność, Cztery miesiące po tym naświetleniu w widmie fotoluminescencji obserwuje się dodatkową emisję dla 540 nm wzbudzaną przez absorpcję dla 225 nm i 411 nm.

15

Optical and electrical characterization of BixSe1−x thin films

80%

Ibrahim M. M. , Fayek S. A. , Amin G. A. M. , Elnagar D. M.

Materials Science Poland

|

2016

|

tom Vol. 34, No. 2

460--469

EN

Bulk samples of the BixSe1-x system with (x = 0, 5, and 10) were prepared using conventional melt quenching technique. Thin films were then deposited by thermal evaporation technique under high vacuum conditions from the prepared bulk samples. Effect of Bi substitution on surface morphology, electrical and optical properties of BixSe1-x thin films was studied. X-ray diffraction studies showed the formation of nanocrystalline clusters at Bi concentration x = 10. Formation of these clusters resulted in a rough surface which was confirmed by AFM measurements. The film surface was smooth, with RMS roughness of 0.0124 nm for Bi5Se95. For Bi10Se90, the RMS roughness increased to 3.93 nm indicating the formation of Bi2Se3 clusters. A simple hot probe technique showed a transition from p-type to n-type due to Bi incorporation. Charge transport mechanisms were investigated by temperature dependent DC electrical conductivity measurements in the temperature range of 209 K to 313 K. Electrical activation energy (ΔE) of the films with different Bi concentrations was found to exhibit a notable change at the p to n transition. At low temperature, the conduction was in reasonable agreement with Mott’s condition of variable range hopping. Mott parameters and the density of localized states near Fermi level were evaluated and correlated with the structural changes resulting from Bi addition. In addition, a red shift of the optical absorption edge of the films under study caused by Bi-Se substitution was observed. Slight changes in the optical parameters were observed with the γ-irradiation. Addition of Bi atoms could be used to tailor the structural, electrical and optical properties of chalcogenide materials such as junctionless photovoltaic devices.

16

Structural and Optical Properties of Fe2O3 - NiO mixed Thin Films Prepared by Chemical Spray Pyrolysis

80%

Mohmmed N. J. , Habubi M. N.

|

tom Vol. 14, iss. 1

65--85

EN

Mixed Fe2O3 - NiO thin films have been prepared by chemical Spray pyrolysis technique onto glass substrate preheated to 450 °C. The thickness of thin films was found to be (400 ±20) nm. XRD measurements reveal that all the film exhibit polycrystalline hexagonal wrutzite with a preferred orientation along (104) plane for pure and 10 % and 20 % Ni, while for the rest the structure was amorphous. AFM analysis indicate a nanostructure for all the films. The optical energy gap was found to be increased from optical transitions seems to be direct and the optical energy gap seems to be increased from 2.5 to 2.69 eV as the percentage of NiO increase.

17

Controllable synthesis of ZnO nanostructures by a simple solution route

80%

Wang J. , He S. , Zhang S. , Li Z. , Yang P. , Jing X. , Zhang M. , Jiang Z.

|

tom Vol. 27, No. 2

477--484

EN

Flower-shaped ZnO nanostructures, composed of ZnO nanorods, and sphere-shaped ZnO nanoclusters, composed of ZnO nanosheets, were synthesized by reacting zinc acetate dehydrate with sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180 °C for 4 h in solution. The thickness of individual nanosheets is about 40-60 nm. The nanorods are of hexagonal shape with sharp tips, and have basic diameters of ca. 450-550 nm. The ZnO nanostructures were characterized by scanning electron microscropy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared, and Raman scattering measurements. The results demonstrated that the synthesized products are single crystalline with wurtzite hexagonal phase, the sphere-shaped ZnO grew in the [100] direction and the flower-shaped ZnO grew in the [001] direction.

18

Synthesis in aqueous phase and characterization of silver nanorods and nanowires

80%

Zhou J. , Zhou G. , Wang R. , Lu M.

|

tom Vol. 27, No. 1

73--78

EN

Silver nanorods and nanowires have been synthesized via a chemical process in aqueous phase by using ascorbic acid as a reducing agent and anionic surfactant dodecyl benzene sulfonic acid sodium (SDBS) as a capping agent. The products were characterized by X-ray diffraction (XRD) techniques and transmission electron microscopy (TEM). Experimental results indicated that the concentration of ascorbic acid played a critical role in the formation of the silver nanorods and nanowires. The optical properties were investigated. The prepared nanostructures displayed a very strong absorption band at room temperature.

19

Electronic and gas sensing properties of soluble phthalocyanines

80%

Pochekailov S. , Rais D. , Nešpůrek S. , Rakušan J. , Karásková M.

|

tom Vol. 27, No. 3

781--795

EN

Some optical and electrical properties of 3-diethylamino-1-propylsulfonamide substituted zinc and metal-free phthalocyanines are presented. These materials are sensitive to NO2 even at concentrations as low as 0.1-2.5 ppm. Electrical conductivity and photoconductivity were used as the detection methods.

20

Inherent optical properties and particulate matter distribution in summer season in waters of Hornsund and Kongsfjordenen, Spitsbergen

80%

Sagan S. , Darecki M.

Oceanologia

|

2018

|

tom No. 60 (1)

65--75

EN

Two Spitsbergen fjords, Hornsund and Kongsfjorden, are known for being under different hydrological regimes. The first is cold, separated from warm Atlantic water by East Spitsbergen Current, while Kongsfjorden is frequently penetrated by relatively warm Atlantic water. On the other hand, both are under strong influence of water discharge from glaciers and land freshwater input. During the period of observation in both fjords a dominant water mass was Surface Water, which originates mainly from glacial melt. The presence of suspended matter introduced with melt water in Surface Water is reflected by highest values of light attenuation and absorption coefficients recorded in areas close to glacier both in Hornsund and Kongsfjorden. In Hornsund the maximum light attenuation coefficient cpg(555) was 5.817 m−1 and coefficient of light absorption by particles ap(676) = 0.10 m−1. In Kongsfjorden the corresponding values were 26.5 m−1and 0.223 m−1. In Kongsfjorden suspended matter of the size class 20-200 μm dominated over fractions smaller than 20 μm while in Hornsund dominating size fraction was 2-20 μm. The results provide an evidence of considerable range of variability of the optical properties mainly due to glacial and riverine runoff. The scale of variability of particulate matter in Kongsfjorden is bigger than in Hornsund. Most of the variability in Hornsund can be attributed to glaciers discharge and a presence of particles of mineral origin, while in Kongsfjorden the organic and mineral particles contribute almost equally to defining the optical properties of water.