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1
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Determination of thin film refractive index and thickness by means of film phase thickness

100%
Nenkov M., Pencheva T.
Open Physics
|
2008
|
vol. 6
|
issue 2
332-343
EN
A new approach for determination of refractive index dispersion n(λ) (the real part of the complex refractive index) and thickness d of thin films of negligible absorption and weak dispersion is proposed. The calculation procedure is based on determination of the phase thickness of the film in the spectral region of measured transmittance data. All points of measured spectra are included in the calculations. Barium titanate thin films are investigated in the spectral region 0.38–0.78 μm and their n(λ) and d are calculated. The approach is validated using Swanepoel’s method and it is found to be applicable for relatively thin films when measured transmittance spectra have one minimum and one maximum only.
2
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First-principles studies of the electronic structure and optical properties of AgBO3 (B=Nb,Ta) in the paraelectric phase

76%
Cabuk S., Simsek S.
Open Physics
|
2008
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vol. 6
|
issue 3
730-736
EN
The electronic energy-band structure, density of states (DOS), and optical properties of AgBO3 in the paraelectric cubic phase have been studied by using density functional theory within the local density approximation for exchange-correlation for the first time. The band structure shows a band gap of 1.533 eV (AgNbO3)and 1.537 eV (AgTaO3)at (M-⌈)point in the Brillouin zone. The optical spectra of AgBO3 in the photon energy range up to 30 eV are investigated under the scissor approximation. The real and imaginary parts of the dielectric function and - thus the optical constants such as reflectivity, absorption coefficient, electron energy-loss function, refractive index, and extinction coefficient - are calculated. We have also made some comparisons with related experimental and theoretical data that is available.
3
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Ab initio calculations of electronic and optical properties in O-doped LiF crystal

76%
Guo M., Zhang X., Gu H., Wang N.
|
EN
We present a first-principle study of electronic and optical properties in pure LiF and O-doped LiF crystals. The pure LiF crystal exhibits a wide band gap while the O-doped LiF crystal shows the less band gap due to the contribution of O 2p. Some optical constants, such as dielectric functions, reflectivity and the refractive index, have been performed. The calculated reflectivity and refractive index from the pure LiF crystal agree with the experimental and recently calculated results in the low-energy range. Meanwhile, the optical properties have also been predicted from the O-doped LiF crystal. The absorption band in 200 nm has been observed, which is relatively close to the experimental result.
4
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Left-handed chiral metamaterials

64%
Sabah C.
Open Physics
|
2008
|
vol. 6
|
issue 4
872-878
EN
In this work, the concept of left-handed chiral metamaterials is analyzed by emphasizing their optical ability on the rotation of the plane of polarization of a wave. The possibilities of a negative phase velocity, negative and positive propagation constants, and basic electromagnetic properties of this novel medium are also presented. After the characterization of left-handed chiral metamaterial, we provide a reflection and transmission study for two planar boundaries of nonchiral-left-handed chiral metamaterial for normal angles of incidence. Some numerical results are also provided to validate the formulation found in the analysis and to show the role of the chirality in the propagation constants, phase velocities, reflection and transmission.
5
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Optical absorption in PECVD deposited thin hydrogenated silicon in light of ordering effects

64%
Müllerová J., Vavruňková V., Šutta P.
Open Physics
|
2009
|
vol. 7
|
issue 2
315-320
EN
We report results obtained from measurements of optical transmittance spectra carried out on a series of silicon thin films deposited by plasma-enhanced chemical vapour deposition (PECVD) from silane diluted with hydrogen. Hydrogen dilution of silane results in an inhomogeneous growth during which the material evolves from amorphous hydrogenated silicon (a-Si:H) to microcrystalline hydrogenated silicon (µc-Si:H). Spectral refractive indices and absorption coefficients were determined from transmittance spectra. The spectral absorption coefficients were used to determine the Tauc optical band gap energy, the B factor of the Tauc plots, E 04 (energy at which the absorption coefficient is equal to 104 cm−1), and the Urbach energy as a function of the hydrogen dilution. The results were correlated with microstructure, namely volume fractions of the amorphous and crystalline phase with voids, and with the grain size.
6
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Ab-initio calculation of band structure and linear optical properties of SbSI in para- and ferroelectric phases

64%
Akkus H., Mamedov A.
Open Physics
|
2007
|
vol. 5
|
issue 1
25-34
EN
An ab-initio pseudopotential calculation has been performed by using density functional methods within the local density approximation (LDA) to investigate the band structure and optical properties of the ferroelectric-semiconductor SbSI in the para- and ferroelectric phases. It has been shown that SbSI has an indirect gap in both phases (1.45 eV and 1.49 eV in the para- and ferroelectric phases respectively) and that the smallest direct gap is at the S point of the Brillouin zone (1.56 eV and 1.58 eV in the para- and ferroelectric phases respectively). Furthermore, it is shown that first-order phase transition, from the paraelectric phase to the ferroelectric phase (the transiton temperature is about 22 °C), does not change the nature of the band gap. Moreover, the linear frequency dependent dielectric function, including self-energy effects, has been calculated along the c-polar axis in the para- and ferroelectric phases.
7
Content available remote

Relative Reflection Difference as a Method for Measuring the Thickness of the Exfoliated MoSe₂ Layers

64%
Łempicka K., Norowski K., Grzeszczyk M., Król M., Lekenta K., Babiński A., Piętka B., Szczytko J.
Acta Physica Polonica A
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2017
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vol. 132
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issue 2
316-318
EN
We propose a method for measuring the thickness of the exfoliated MoSe₂ layers deposited on Si/SiO₂ substrate, based on the reflectance measurements performed with laser light illumination at two different wavelengths: red and green from confocal microscope at room temperature. We demonstrate the correlation between the number of layers in a flake and the value of its relative reflection difference. We applied the transfer matrix method to calculate the reflectivity and verify our experimental results. The approach proposed by us allows for fast and automatic verification of the exfoliated MoSe₂ layers thickness on large areas of the substrate.
8
Content available remote

Electronic and optical properties of ZnSxSe1−x alloys

64%
Feng Z., Hu H., Cui S.
Open Physics
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2009
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vol. 7
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issue 2
340-344
EN
A series of calculations from first principles have been carried out to study structural, electronic, and optical properties of ZnSxSe1−x alloys. Our results show that the lattice constant scales linearly with sulfur composition. The imaginary parts of the dielectric function are calculated, which are in good agreement with the experimental data. We have also interpreted the origin of the spectral peaks on the basis of band structure and density of states. Additionally, we find that no bowing effect in the absorption edge is observed, unlike other II-VI semiconductor alloys.
9
Content available remote

Absorption of Twisted and Linearly Polarized Light in Graphene with Rashba Spin-Orbit Interaction

64%
Inglot M., Dugaev V.
Acta Physica Polonica A
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2017
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vol. 132
|
issue 1
193-195
EN
Theoretical analysis of the electron excitations in graphene on substrate by twisted, linear and circular polarization light is presented. We use a model of graphene with constant Rashba spin-orbit interaction. In this case, the band structure of electrons includes four energy bands. The main objective of this work is to compare light absorptions in graphene for different kinds of light, namely, twisted (with nonzero orbital angular momentum) and linear polarized light. The orbital angular momentum light is characterized by some parameters q and l, which can modify the response, while for the linear polarization, the absorption is modified only in the region determined by the Rashba spin-orbit coupling α.
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