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Abstract

Properties of excitons confined to potential fluctuations due to indium distribution in the wetting layer which accompany self-assembled InAs/GaAs quantum dots are reviewed. Spectroscopic studies are summarized including time-resolved photoluminescence and corresponding single-photon emission correlation measurements. The identification of charge states of excitons is presented which is based on results of a theoretical analysis of interactions between the involved carriers. The effect of the dots’ environment on their optical spectra is also shown.

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Authors and Affiliations

A. Babiński
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Abstract

This study offers a new method to synthesize facilely willemite (Zn2SiO4) based phosphor at the temperature of 800 °C. The ZnO-SiO2 nanocomposite was calcined at different temperatures between 500 and 1000 °C. The structural, morphological and optical properties of the nanocomposite obtained at various calcination temperatures were studied using different techniques. The FT-IR, XRD and the UV-vis result confirmed the formation of willemite phase. The precursor was confirmed to be amorphous by XRD at room temperature, but upon calcination temperature at 500 °C, it was transformed into a crystalline structure. The crystallinity and the particle size of the nanocomposite increase as the calcination temperature were increased as revealed by XRD and TEM measurement. The sample exhibits a spherical morphology from 500 to 800 °C and dumbbell-like morphology above 800 °C as shown by the FESEM images. The absorption spectrum suffers intense in lower temperature and tends to shift to lower wavelength in the UV region as the calcination temperature increases. The band gap values were found to be increasing from 3.228-5.550 eV obtained between 500 to 1000 °C, and all the results confirm the formation of willemite phase at 800 °C.
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Authors and Affiliations

Ibrahim Mustapha Alibe
Khamirul Amin Matori
Haj Abdul Aziz Sidek
Yakoob Yazid
Elias Saion
Ali Mustapha Alibe
Mohd Hafiz Mohd Zaid
Ali Engku Abd Ghapur Engku
Tasiu Zangina
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Abstract

The S-7 borehole log from the Sumina area (USCB Poland) revealed the presence of three basaltic veins

originating from a basalt dyke. Coal interlayers in the rocks surrounding the basaltic veins have been coked to

form natural coke. Photometric measurements revealed that the optical properties of the studied natural coke

samples are characteristic of semi-graphite (Rmax > 9%). The natural coke matrix of all of the analyzed samples

has a biaxial negative optical character. Vitrinite in the examined natural coke samples is characterized by a

lower optical anisotropy than that of the natural matrix and it has a biaxial positive optical character. Vitrinite

in almost all samples taken at locations more distant from the intrusion has a biaxial positive optical character.

A reversal of the changes of the true maximum vitrinite reflectance and bireflectance with changing distance

from the second basaltic vein has been observed. The temperature regime that acted upon the dispersed organic

matter located in the immediate vicinity of the intrusion, estimated on the basis of the selected experimental

data, is suggested to be higher than 750 °C.

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Authors and Affiliations

Zdzisław Adamczyk
Magdalena Kokowska-Pawłowska
Joanna Komorek
Agnieszka Klupa
Małgorzata Lewandowska
Jacek Nowak
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Abstract

The growing interest in one-dimensional tin oxide-based nanomaterials boosts research on both high-quality nanomaterials as well as production methods. This is due to the fact that they present unique electrical and optical properties that enable their application in various (opto)electronic devices. Thus, the aim of the paper was to produce ceramic SnO₂ nanowires using electrospinning with the calcination method, and to investigate the influence of the calcination temperature on the morphology, structure and optical properties of the obtained material. A scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) were used to examine the morphology and chemical structure of obtained nanomaterials. The optical properties of manufactured one-dimensional nanostructures were investigated using UV-Vis spectroscopy. Moreover, based on the UV-Vis spectra, the energy band gap of the prepared nanowires was determined. The analysis of the morphology of the obtained nanowires showed that both the concentration of the precursor in the spinning solution and the calcination temperature have a significant impact on the diameter of the nanowires and, consequently, on their optical properties.
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Authors and Affiliations

Tomasz Tański
1
ORCID: ORCID
Weronika Smok
1
ORCID: ORCID
Wiktor Matysiak
1

  1. Department of Engineering Material and Biomaterials, Silesian University of Technology, ul. Konarskiego 18A, 44-100 Gliwice, Poland
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Abstract

Crystals of PbTiO3 and 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 were obtained by the flux growth method whereas crystals of (Na0.5Bi0.5)TiO3 were growth by the Czochralski method. Raman spectroscopy and polarized light microscopy were performed at room temperature. The Raman spectra of 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 shown significant changes comparing to the base materials PbTiO3 and (Na0.5Bi0.5)TiO3. A domain structure was investigated by use polarized light microscopy. Dielectric permittivity measurements were carried out in the temperature range from 20°C to 550°C and a frequency from 1 kHz to 1 MHz. These showed higher dielectric permittivity for the crystals 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 than the source materials PbTiO3 and (Na0.5Bi0.5)TiO3.

The high value of dielectric constant makes it possible to applied 0.9PbTiO3-0.1(Na0.5Bi0.5)TiO3 as efficient dielectric medium in a capacitors. The small size of the domain structure with the easy possibility of switching by application of an external electric field, give opportunities to apply these materials to FRAM memory applications. Moreover, the high sensitivity of these materials to the surrounding gases e.g. ammonia, chlorine, hydrogen, etc., allows the construction of sensor devices.

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Authors and Affiliations

P. Czaja
ORCID: ORCID
M. Piasecki
M.B. Zapart
J. Suchanicz
K. Konieczny
J. Michniowski
D. Sitko
G. Stachowski
K. Kluczewska-Chmielarz
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Abstract

The aim of this work was to produce a thin SnO2 film by a technique combining the sol-gel method and electrospinning from a solution based on polyvinylpyrrolidone and a tin chloride pentahydrate as a precursor. The spinning solution was subjected to an electrospinning process, and then the obtained nanofiber mats were calcined for 10 h at 500°C. Then, the scanning electron microscopy morphology analysis and chemical composition analysis by X-ray microanalysis of the manufactured thin film was performed. It was shown that an amorphous-crystalline layer formed by the SnO2 nanofiber network was obtained. Based on the UV-Vis spectrum, the width of the energy gap of the obtained layer was determined.

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Authors and Affiliations

W. Matysiak
T. Tański
W. Smok
S. Polishchuk
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Abstract

In this article, synthesis, electronic and optical properties of an N-cyclohexyl-acrylamide (NCA) molecule are described based on different solvent environments and supported by theoretical calculations. Theoretical calculations have been carried out using a density function theory (DFT). Temperature dependence of the sample electrical resistance has been obtained by a four-point probe technique. Experimental and semi-theoretical parameters such as optical density, transmittance, optical band gap, refractive index of the NCA for different solvents were obtained. Both optical values and electrical resistance values have shown that NCA is a semiconductor material. The values of HOMO and LUMO energy levels of the headline molecule indicate that it can be used as the electron transfer material in OLEDs. All results obtained confirm that the NCA is a candidate molecule for OLED and optoelectronic applications.

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Authors and Affiliations

E. Tanış
N. Çankaya
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Abstract

Abstract A conductive boron-doped diamond (BDD) grown on a fused silica/quartz has been investigated. Diamond thin films were deposited by the microwave plasma enhanced chemical vapor deposition (MW PECVD). The main parameters of the BDD synthesis, i.e. the methane admixture and the substrate temperature were investigated in detail. Preliminary studies of optical properties were performed to qualify an optimal CVD synthesis and film parameters for optical sensing applications. The SEM micro-images showed the homogenous, continuous and polycrystalline surface morphology; the mean grain size was within the range of 100-250 nm. The fabricated conductive boron-doped diamond thin films displayed the resistivity below 500 mOhm cm-1 and the transmittance over 50% in the VIS-NIR wavelength range. The studies of optical constants were performed using the spectroscopic ellipsometry for the wavelength range between 260 and 820 nm. A detailed error analysis of the ellipsometric system and optical modelling estimation has been provided. The refractive index values at the 550 nm wavelength were high and varied between 2.24 and 2.35 depending on the percentage content of methane and the temperature of deposition.

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Authors and Affiliations

Robert Bogdanowicz
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Abstract

Constantly developing nanotechnology provides the possibility of manufacturing nanostructured composites with a polymer matrix doped with ceramic nanoparticles, including ZnO. A specific feature of polymers, i.e. ceramic composite materials, is an amelioration in physical properties for polymer matrix and reinforcement. The aim of the paper was to produce thin fibrous composite mats, reinforced with ZnO nanoparticles and a polyvinylpyrrolidone (PVP) matrix obtained by means of the electrospinning process and then examining the influence of the strength of the reinforcement on the morphology and optical properties of the composite nanofibers. The morphology and structure of the fibrous mats was examined by a scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) and Fourier-transform infrared spectroscopy (FTIR). UV –Vis spectroscopy allowed to examine the impact of zinc oxide on the optical properties of PVP/ZnO nanofibers and to investigate the width of the energy gap.

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Authors and Affiliations

W. Matysiak
T. Tański
M. Zaborowska
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Abstract

Thin films were prepared based on cellulose polymer doped with different ratios of natural dye derived from Portulaca grandiflora concentrations. The polymer and natural dye were extracted from eco-friendly materials—the cell walls of millet husks and Portulaca grandiflora, respectively. The spray pyrolysis technique was applied to prepare thin film samples to control the film morphology and reduce the roughness of the surface. Optical microscope and Fourier transform infrared were used to analyse structural, morphological, and functional groups for all samples, respectively. The peak absorbance, extinction coefficient, optical bandgap, Urbach energy, and optical conductivity for the thin films were determined using ultraviolet-visible spectroscopy. The results show an enhancement in the optical characteristics when the natural cellulose is doped with a dye. Doping cellulose with 5% P. grandiflora has led to a considerable reduction in the energy bandgap (to 1.95 eV), compared to the sample doped with 1%.
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Authors and Affiliations

Tahseen Alaridhee
1
ORCID: ORCID
Mohammed T. Obeed
1
ORCID: ORCID
Fatima H. Malk
1
ORCID: ORCID
Baheya A. Dhahi
1

  1. Department of Material Science, Polymer Research Centre, University of Basrah, Iraq
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Abstract

Titania dioxide (TiO2) layers were synthesized via the acid-catalysed sol-gel route using titania (IV) ethoxide, and then annealed at temperatures varying in the range of 150–700 °C. The research concerned the effect of annealing temperature on the structure of TiO2 layers, their surface morphology, and their optical properties. Further, X-ray diffractometry, and Raman spectroscopy were used to determine the structure of TiO2 layers. Scanning electron and atomic force microscopy were used to study the surface morphology of TiO2 layers. Transmittance, reflectance, absorption edge, and optical homogeneity were investigated by UV-VIS spectrophotometry, while the refractive index and thicknesses of TiO2 layers were measured using a monochromatic ellipsometer. Chromatic dispersion characteristics of the complex refractive index were determined using spectroscopic ellipsometry. Structural studies have shown that the TiO2 layers annealed at temperatures up to 300 °C are amorphous, while those annealed at temperatures exceeding 300 °C are polycrystalline containing only anatase nanocrystals with sizes increasing from 6 to 20 nm with the increase of the annealing temperature. Investigations on the surface morphology of TiO2 layers have shown that the surface roughness increases with the increase in annealing temperature. Spectrophotometric investigations have shown that TiO2 layers are homogeneous and the width of the indirect optical band gap varies with annealing temperature from 3.53 eV to 3.73 eV.

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Authors and Affiliations

Magdalena Zięba
1
ORCID: ORCID
Cuma Tyszkiewicz
1
ORCID: ORCID
Ewa Gondek
2
ORCID: ORCID
Katarzyna Wojtasik
2
ORCID: ORCID
Jacek Nizioł
3
ORCID: ORCID
Dominik Dorosz
4
ORCID: ORCID
Bartłomiej Starzyk
4
ORCID: ORCID
Patryk Szymczak
4
ORCID: ORCID
Wojciech Pakieła
5
ORCID: ORCID
Roman Rogoziński
1
ORCID: ORCID
Paweł Karasiński
1
ORCID: ORCID

  1. Department of Optoelectronics. Silesian University of Technology, ul. B. Krzywoustego 2, 44-100 Gliwice, Poland
  2. Department of Physics, Cracow University of Technology, ul. Podchorążych 1, 30-084 Kraków, Poland
  3. Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland
  4. Faculty of Materials Science and Ceramics AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Krakow, Poland
  5. Department of Engineering Materials and Biomaterials, Silesian University of Technology, ul. Konarskiego 18a, 44-100 Gliwice, Poland
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Abstract

Structural and optical properties of graphene with a vacancy and B, N, O and F doped graphene have been investigated computationally using density functional theory (DFT). We find that B is a p-type while N, O and F doped graphene layers, as well as graphene with a vacancy are n-type semiconductors. Optical properties for both cases of in plane (E ⊥ c) and out of plane (E || c) polarization of light are investigated. It is observed that with the increase in the number of electrons entering the supercell, the amount of absorption of the system decreases and the absorption peaks are transferred to higher energies (blue shift).

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Authors and Affiliations

M. Goudarzi
S.S. Parhizgar
J. Beheshtian
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Abstract

Microstructures are an important link between materials processing and performance, and microstructure control is essential for any materials processing route where the microstructure plays a major role in determining the properties. In this work, silver-doped titanium dioxide (Ag/TiO2) thin film was prepared by the sol-gel method through the hydrolysis of titanium tetra-isopropoxide and silver nitrate solution. The sol was spin coated on ITO glass substrate to get uniform film followed by annealing process for 2 hours. The obtained films were annealed at different annealing temperatures in the range of 300°C-600°C in order to observe the effect on crystalline state, microstructures and optical properties of Ag/TiO2 thin film. The thin films were characterized by X-Ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis spectrophotometry. It is clearly seen, when the annealing temperature increases to 500°C, a peak at 2θ = 25.30° can be seen which refers to the structure of TiO2 tetragonal anatase. The structure of Ag/TiO2 thin film become denser, linked together, porous and uniformly distributed on the surface and displays the highest cut-off wavelength value which is 396 nm with the lowest band gap value, which is 3.10 eV.
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Authors and Affiliations

A.R. Kamrosni
1
ORCID: ORCID
C.H. Dewi Suryani
1
ORCID: ORCID
A. Azliza
1
ORCID: ORCID
A.B.A. Mohd. Mustafa
1
ORCID: ORCID
M.S. Mohd. Arif Anuar
1
ORCID: ORCID
M. Norsuria
1
ORCID: ORCID
V. Chobpattana
2
ORCID: ORCID
L. Kaczmarek
3
ORCID: ORCID
B. Jeż
4
ORCID: ORCID
M. Nabiałek
4
ORCID: ORCID

  1. Universiti Malaysia Perlis, (UniMAP), Center of Excellence Geopolymer & Green Technology (CEGeoGTech), School of Materials Engineering, 02600 JalanKangar- Arau, Perlis, Malaysia
  2. Rajamangala University of Technology Thanyaburi (RMUTT), Fac ulty of Engineering, Department of Materials and Metallurgical Engineering, Thailand
  3. Lodz University of Technology (TUL), Instititute of Materials Science and Engineering, 1/15 Stefanowskiego Str., 90-924 Lodz, Poland
  4. Częstochowa University of Technology, Faculty of Production Engineering and Materials Technology, Department of Physics, 19 Armii Krajowej Av., 42-200 Częstochowa, Poland
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Abstract

The electronic, magnetic, and optical properties of PtCoBi half-Heusler compound [001] surfaces and its bulk state have been investigated in the framework of density functional theory using GGA approximation. The half-metallic behaviors of CoBi-term, CoPt-term and PtBi-term decrease with respect to its bulk state. The spin polarization at the Fermi level is 73.2% for the bulk state, and it is –64.4% and –64.1% for the CoBi-term and PtBi-term, respectively while less polarization has been observed for the ­CoPt-term. All terminations have given almost similar optical responses to light. Plasmon oscillations for the terminations occur in the range of 12.5 to 14.5 eV (21 to 22 eV) along xx (zz), and it occurs at 23 eV for the bulk state. The refractive index for the bulk and all three terminations is very high in the infrared and visible areas, meaning a very strong metallic trend in these compounds. The phenomenon of super-luminance occurs for the incident light with energy exceeding 5.5 eV for all three terminations, and it occurs in the range of 10 eV for the bulk mode. These terminations show transparent behavior after the energy of 10 eV.
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Authors and Affiliations

Hamed Rezazadeh
1
ORCID: ORCID
Mohamadreza Hantehzadeh
1
ORCID: ORCID
Arash Boochani
2
ORCID: ORCID

  1. Islamic Azad University, Department of Physics, Science and Research Branch, Tehran, Iran
  2. Islamic Azad University, Department of Physics, Kermanshah Branch, Kermanshah, Iran
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Abstract

Mechanical, electronic, thermodynamic phase diagram and optical properties of the FeVSb half-Heusler have been studied based on the density functional theory (DFT) framework. Studies have shown that this structure in the MgAgAs-type phase has static and dynamic mechanical stability with high thermodynamic phase consistency. Electronic calculations showed that this compound is a p-type semiconductor with an indirect energy gap of 0.39 eV. This compound’s optical response occurs in the infrared, visible regions, and at higher energies its dielectric sign is negative. The Plasmon oscillations have occurred in 20 eV, and its refraction index shifts to zero in 18 eV.
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Authors and Affiliations

A. Bagheri
1
A. Boochani
2
S.R. Masharian
1
F.H. Jafarpour
3

  1. Department of Physics, Hamedan Branch, Islamic Azad University, Hamedan, Iran
  2. Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
  3. Physics Department, Bu-Ali Sina University, 65174-4161 Hamedan, Iran
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Abstract

In the present work, Hydroxyapatite synthesis was carried out using hydrothermal method with calcium nitrate tetrahydrate (Ca(NO 3) 2.4H 2O) and fosfor pentaoksit (P 2O 5) as precursors. For the hydrothermal method, constant reaction temperature (180°C) and different reaction times (6 hours, 12 hours, 18 hours and 24 hours) were determined. The samples produced were divided into two groups. Four samples were not heat treatment; four samples were heat treatment at 700°C for 1 hour. The obtained products were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) techniques, X-ray diffraction (XRD) and UV-Vis spectrometer. SEM photos showed that the Hydroxyapatite powders produced are in the form of the agglomerate. According to EDS results, Hydroxyapatite samples are of high purity. XRD’s findings confirm that the diffraction peaks correspond to the pure phase of Hydroxyapatite. A general decrease was observed in the energy band gap of the samples with increasing hydrothermal reaction time.
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Authors and Affiliations

Nida Kati
1
ORCID: ORCID
Sermin Ozan
1
ORCID: ORCID
Tülay Yildiz
1
ORCID: ORCID
Mehmet Arslan
1
ORCID: ORCID

  1. Fırat Unıversity, Faculty of Technology, Metallurgical and Materials Engineering Department, 23200, Elazığ, Turkiye
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Abstract

The effects of hydrogen absorption and manganese substitution on structural, electronic, optical, and thermoelectric properties of silicon-carbon nanotubes (SiCNT) are studied using the density functional theory and the GGA approximation. An examination of the PDOS curves and the electronic band structure showed that the Mn substitution leads to an increase in magnetic anisotropy and the occurrence of semi-metallic behavior and that the hydrogen absorption shifts the band gap toward the lower energies. A study of these nanostructures’ thermoelectric behavior reveals that the H absorption leads to a significant escalation in the figure of merit of the SiCNT to about 1.6 in the room temperature range. The effects of the H absorption on this nanotube’s optical properties, including the dielectric functions and its absorption spectra, are also investigated.
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Authors and Affiliations

Amir Toofani Shahraki
1
Heydar Ali Shafiei Gol
1
Salimeh Kimiagar
2
Naser Zare Dehnavi
1

  1. Department of Physics, Central Tehran Branch, Islamic Azad University, Tehran, Iran
  2. Nano Research Lab (NRL), Department of Physics, Central Tehran Branch, Islamic Azad University, Tehran, Iran
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Abstract

In this work, the electronic structure and optical behavior and the thermoelectric performance of the known HfNiSn compound have been studied under the substitution of Mn transition metal instead of Ni atoms. Necessary calculations are performed in the framework of DFT first principles studies by applying generalized gradient approximation (PBE-GGA) as well as solving Boltzmann’s semi-classical equations. The entering Mn leads to a change in the electronic structure of HfNiSn and the occurrence of half-metallic ferromagnetic behavior with 100% polarization at the Fermi level. The maximum ZT value obtained for HfMnSn shows that HfNiSn would be suitable for thermoelectric applications at room temperature, both in pure and Mn presence. The examination of optical parameters also indicates good absorption in the visible range for this compound in all cases.
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Authors and Affiliations

M. Mirmehdi
1
A. Boochani
2
S.R. Masharian
1

  1. Department of Physics, Hamedan Branch, Islamic Azad University, Hamedan, Iran
  2. Department of Physics, Kermanshah Branch, Islamic Azad University, Kermanshah, Iran
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Abstract

A series of copper oxide thin films were synthesized through direct current magnetron sputtering on glass and silicon substrates with various process parameters. Initially, optical microscopy images and their histograms were analyzed to determine the optical quality of the obtained layers and then histograms were created using Image Histogram Generator software. Next, the morphology, and cross-section and layer composition of the samples were evaluated. Finally, the transmission spectra of the thin films were recorded. Transmittance and reflection spectra of the UV–vis analysis were utilized to calculate the optical band gap, the extinction coefficient, and the absorption coefficient of the oxidized layers. Samples showed low transmittance (up to 40%) in the region of 400 to 1000 nm. The mean absorption coefficient varied from ~3 · 105 to ~6 · 105 1/cm and from ~2 · 105 to ~4 · 105 1/cm in the region of 2 eV to 3.5 eV. The extinction coefficient ranged from 0 to 0.11 in the region from 300 to 3000 nm. Reflectance of the samples was ~20% in the region of 1000 to 2500 nm and ranged from 20%-50% in the region of 1000 to 3000 nm. We verified the process parameters of the Cu2O structure to improve the quality as a buffer layer. On the basis of this preliminary analysis, we propose the most promising and future-oriented solutions in photovoltaic applications.

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Authors and Affiliations

P. Sawicka-Chudy
G. Wisz
M. Sibiński
M. Cholewa
P. Potera
Ł. Głowa
R. Pawełek
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Abstract

Composition effect on electro-optic (EO) properties of a LiNbO3 (LN) single-crystal has been investigated in a Li2O-content range of 47.0–49.95 mol%. Some non-congruent LN crystals with different Li2O-contents were prepared by performing Li-deficient or Li-rich vapour transport equilibration treatments on as-grown congruent LN crystals. Unclamped EO coefficients γ13 and γ33 of these samples were measured by a Mach–Zehnder interferometric method. The measurements show that in the Li-deficient regime both γ13 and γ33 increase by ∼8% as Li2O-content decreases from the congruent 48.6 mol% to the 47.0 mol% in the Li-deficient regime. The feature is desired for the EO application of the Li-deficient crystal. In the near-stoichiometric regime, both γ13 and γ33 reveal a non-monotonic dependence. As the Li2O-content increases from the 48.6 mol%, the EO coefficient decreases. Around Li2O-content 49.5 mol%, a minimum is reached. After that, the EO coefficient recovers slowly. At the stoichiometric composition, it recovers to a value close to that at the congruent point. Comparison shows that different crystal growth methods give rise to different defect structure features and hence different composition effects.

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Authors and Affiliations

J.-Q. Xu
W.-Y. Du
Q. Sun
W.-H. Wong
D.-Y. Yu
E.Y.-B. Pun
D.-L. Zhang
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Abstract

Metal nanoshells are a type of nanoparticle composed by a dielectric core and a metallic coating. These nanoparticles have stimulated interest due to their remarkable optical properties. In common with metal colloids, they show distinctive absorption peaks at specific wavelengths due to surface plasmon resonance. However, unlike bare metal colloids, the wavelengths at which resonance occurs can be tuned by changing the core radius and coating thickness. One basic application of such property is in medicine, where it is hoped that nanoshells with absorption peaks in the near−infrared can be attached to cancerous cells. In this paper, we study the changes of optical response in visible and near infrared wavelengths from single to randomly distributed clusters of nanoshells. The results were obtained using a novel formulation of Mie theory in evanescent wave conditions, with a finite−difference time−domain (FDTD) simulation and experimentally on BaTiO3−gold nanoshells using a scanning near−optical microscope. The results show that the optical signal of a randomly distributed cluster of nanoshells can be supplementary tuned with respect to the case of single nanoshell depending by the geometric configuration of the clusters.

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Authors and Affiliations

A. Cricenti
M. Luce
D. Moroni
O. Salvetti
M. D’Acunto
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Abstract

Photoactive nanofilled nematic is proposed. Stable three-component photoresponsive nanocomposite was prepared from photo-insensitive nanofilled nematic by inclusion of 3 wt.% azobenzene-containing photoactive mesogen 4-(4′-ethoxyphenylazo)phenyl hexanoate (EPH). The host nanofilled nematic was produced from the room-temperature nematic liquid crystal 4-n-heptyl cyanobiphenyl (7CB) and 3 wt.% filler of Aerosil 300 hydrophilic silica nanospheres of size 7 nm. Apparent effect of stimulation with a relatively weak continuous illumination by UV light (375 nm wavelength) takes place for both the alternating-current electric field-dependent optical transmittance and the electro-optic amplitude-frequency modulation by thin films (25 µm thick) of the EPH/aerosil/7CB nanocomposite. The light-stimulated electro-optics of EPH-doped aerosil/7CB films and the corresponding reversible light control are achieved through trans-cis-trans photoisomerization of the photoactive agent EPH. As such, the initial electro-optical response of the studied photoactive nanocomposites is recovered with continuous blue-light illumination. The examined EPH/aerosil/7CB nanocomposites exhibit photo-controllable electro-optical response that is of practical interest.

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Authors and Affiliations

Georgi B. Hadjichristov
Yordan G. Marinov
Alexander G. Petrov
Subbarao Krishna Prasad

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