Temat: 63.22.+m - Prolib Integro

Skocz do pozycji: 1.

Tytuł:: Resonant Raman Spectra of CdTe/ZnTe Self Assembled Quantum Dots
Autorzy:: Romčević, N.
Romčević, M.
Kostić, R.
Stojanović, D.
Abolmasov, B.
Karczewski, G.
Galazka, R.
Tematy:: 63.22.-m
78.30.Fs
78.55.Et; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807840.pdf Link otwiera się w nowym oknie
Opis:: In this paper we present Raman scattering and photoluminescence spectra measured on CdTe/ZnTe self assembled quantum dots. The photoluminescence spectrum has shown two main emission peaks, both connected with existing of quantum dots. One presents direct deexcitation to ground state and the other is optical phonon (οmega = 207.3 $cm^{-1}$)-assisted deexcitation. The registered multiphonon emission process depends on temperature. At low temperature phonon spectra shows line at 450 $cm^{-1}$ (TA + 2LO in ZnTe) and 595 $cm^{-1}$ (2LO + TO(Γ) in ZnTe).
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 2.

Tytuł:: Raman Scattering from Acoustic Phonons Confined in Spherical Nanoparticles
Autorzy:: Kostić, R.
Tematy:: 61.46.Df
63.22.-m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807815.pdf Link otwiera się w nowym oknie
Opis:: Low-frequency Raman scattering from small spherical particles is analyzed. Frequencies of vibrational modes are calculated in elastic continuum approximation, which considers one nanoparticle as homogeneous elastic sphere. Parameters of this model are transverse $(v_T)$ and longitudinal $(v_L)$ sound velocities of material, i.e. elastic properties of bulk material. Frequencies of vibrational modes are scaled as function of mentioned bulk parameters for symmetric l=0 and quadrupolar l=2 spheroidal modes, in the case of stress-free boundary conditions. Calculated values are compared with the low-frequency Raman experimental results from literature (Ge, Si, CdS, CdSe, $CeO_2$, ...). These calculated relations can be practically used to examine nanoparticles of any bulk material. We presented also a procedure how to establish $v_L$ and $v_T$ of material from low-frequency Raman spectra and dimension d of particles.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 3.

Tytuł:: Size Effects on Nanowire Phonon Thermal Conductivity: a Numerical Investigation Using the Boltzmann Equation
Autorzy:: Abouelaoualim, D.
Tematy:: 63.22.+m
87.15.Aa; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2047359.pdf Link otwiera się w nowym oknie
Opis:: Analytical solution of the Boltzmann transport equation for phonon transport in Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire is obtained. Thermal conductivity was calculated from the analytical solution of the Boltzmann transport equation. We calculate the lattice thermal conductivity of Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire as a function of temperature for different wire thicknesses. The results show that thermal conductivity of nanowire can be significantly smaller than the bulk thermal conductivity. We show that low thermal conductivity Bi$\text{}_{0.95}$Sb$\text{}_{0.05}$ nanowire for thermoelectric applications would have a small diameter.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 4.

Tytuł:: Nanocrystalline Materials: Interfaces and Mesoscopic Correlations Studied by Neutron Scattering
Autorzy:: Stuhr, U.
Wagner, W.
Kohlbrecher, J.
van Swygenhoven, H.
Tematy:: 61.46.+w
63.22.+m
75.20.En
75.50.Tt; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/2035459.pdf Link otwiera się w nowym oknie
Opis:: Nanocrystalline materials can exhibit properties which are considerably different from their coarse-grained counterparts, making them unique for basic or applied research and also very promising for potential applications. The topics which are addressed in the present paper are magnetic properties and magnetic correlations on the nanometer scale, mechanical properties, in particular the influence of grain boundaries on the elastic and plastic behaviour, and vibration modes of grain boundary atoms in nanostructured materials.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 5.

Tytuł:: High Pressure Raman Spectroscopy in Carbon Nanotubes
Autorzy:: Kourouklis, G.
Arvanitidis, J.
Christofilos, D.
Ves, S.
Tematy:: 78.67.Ch
78.30.Na
63.22.-m
62.50.-p; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807795.pdf Link otwiera się w nowym oknie
Opis:: This work focuses on the high pressure Raman study of carbon nanostuctures comprising of single- or double-wall carbon nanotubes. The detailed examination of the Raman peaks, especially those attributed to the radial breathing modes of the carbon nanotubes, as a function of pressure provides a wealth of information concerning the pressure response of individual nanotubes as well as the internal-external tube (intratube) interactions. The radial breathing modes of both the internal and the external tubes in double-wall carbon nanotubes show reduced pressure slope values as compared to the corresponding in single-wall carbon nanotubes. The reduced slopes for the internal tubes reflect the pressure screening effect inside the external tubes, while those for the external tubes their structural reinforcement due to the encapsulation of smaller diameter tubes in their interior. Moreover, the magnitude of the pressure screening effect depends strongly on the intratube spacing and thus on the intratube interaction. All the experimental observations are well reproduced qualitatively by means of theoretical calculations based on a simple phenomenological model.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 6.

Tytuł:: Anharmonicity Effects in Nanocrystals Studied by Raman Scattering Spectroscopy
Autorzy:: Dohčević-Mitrović, Z.
Popović, Z.
Šćepanović, M.
Tematy:: 63.22.-m
78.67.Bf
78.30.-j
61.72.uj; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807800.pdf Link otwiera się w nowym oknie
Opis:: Phonon-phonon interactions were investigated in various nanocrystalline powders like anatase $TiO_{2-δ}$, pure $CeO_{2-δ}$ and ceria doped with Nd(Gd) analyzing temperature dependent Raman spectra of these systems. Phonon confinement model based on size, inhomogeneous strain and anharmonic effects was used to properly describe the evident changes present in the Raman spectra of pure and doped ceria nanocrystalline samples. In small particles of pure and doped ceria nanocrystals, when size effects have minor impact on Raman modes, four phonon anharmonic processes prevail under the three-phonon ones. When nanopowdered particles are grown enough size effects provoke changes of the anharmonic interactions when three-phonon coupling prevails over the four-phonon anharmonic processes. In nanocrystalline anatase $TiO_2$ evident blueshift of the most prominent $E_g$ Raman mode probably originates from dominant four-phonon anharmonic interactions.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 7.

Tytuł:: Use of Phonon Confinement Model in Simulation οf Raman Spectra of Nanostructured Materials
Autorzy:: Grujić-Brojčin, M.
Šćepanović, M.
Dohcević-Mitrović, Z.
Popović, Z.
Tematy:: 81.07.Wx
78.30.-j
63.22.-m
07.05.Tp; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807810.pdf Link otwiera się w nowym oknie
Opis:: The simulation of the Raman spectra of nanostructured materials, where the effects of frequency shift and asymmetric broadening of the Raman modes play an important role, can be very useful in systematic characterization of these materials. Use of phonon confinement model for calculating Raman spectra of different nanomaterials is considered both from the viewpoint of different confinement function and the confinement strength, as well as the dimensionality of the confinement model. The phonon dispersion relations and the choice of their approximation are also studied. The influence of particle size distribution on the shape of the calculated spectra is discussed and contributions of Gaussian and asymmetric Gaussian distribution are compared. The effects of average and inhomogeneous strain on the behavior of simulated Raman spectra are also discussed. The results of the phonon confinement model are compared to the experimental spectra of $CeO_2$ and anatase $TiO_2$ nanopowders.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 8.

Tytuł:: Low-Frequency Raman Spectroscopy of Pure and La-Doped $TiO_2$ Nanopowders Synthesized by Sol-Gel Method
Autorzy:: Šćepanović, M.
Aškrabić, S.
Grujić-Brojčin, M.
Golubović, A.
Dohčević-Mitrović, Z.
Kremenović, A.
Popović, Z.
Tematy:: 81.20.Fw
81.07.Wx
78.30.-j
63.22.-m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1807845.pdf Link otwiera się w nowym oknie
Opis:: Pure and La-doped titania $(TiO_2)$ nanopowders are synthesized by sol-gel technology. The crystallite sizes determined by X-ray diffraction measurements range from 10 to 15 nm. Dependence of structural and morphological characteristics of nanopowders on synthesis conditions and $La^{3+}$ content is investigated by the Raman spectroscopy. Very intensive modes observed in the Raman spectra of all nanopowder samples are assigned to anatase phase of $TiO_2$. Additional Raman modes of extremely low intensity can be related to the presence of a small amount of brookite amorphous phase in nanopowders, which is in accordance with the results of X-ray diffraction analysis. The particle size distribution in TiO_2 nanopowders was estimated from the low frequency Raman spectra, using the fact that the phonon modes in nanosized $TiO_2$ observed in the low frequency region (ω <40 $cm^{-1}$) can be well described by the elastic continuum model, assuming that nanoparticles are of perfect spherical shape and isotropic. The nanosized particle distribution obtained by this method is used for the calculation of the frequency and shape of the most intensive $E_g$ Raman mode in anatase $TiO_2$ by the phonon confinement model. The calculated broadening of this mode, associated with the particle size distribution, coincides well with the characteristics of $E_g$ mode observed in measured Raman spectra of $TiO_2$ nanopowders. This confirms the Raman spectroscopy method as a powerful tool for determination of particle size distribution in nanosized materials.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 9.

Tytuł:: Phonon Signatures of a Quantum Impurity with Induced Electron Pairing
Autorzy:: Barański, J.
Domański, T.
Tematy:: 73.63.Kv
73.23.Hk
74.45.+c
74.50.+r
63.22.-m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1374760.pdf Link otwiera się w nowym oknie
Opis:: We analyze the effective spectrum of a vibrating molecule coupled between one conducting and another superconducting electrode. The proximity effect induces electron pairing which is manifested by the subgap quasiparticle peaks (the Andreev states) whose broadening depends on a hybridization with the conducting electrode. On the other hand, the electron-phonon interaction leads to a multilevel structure with the polaronic states separated by the phonon energy. We inspect a combined effect of both these (polaronic and induced pairing) phenomena.
Dostawca treści:: Biblioteka Nauki

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Skocz do pozycji: 10.

Tytuł:: The In$\text{}_{4}$Se$\text{}_{3}$ Crystal as a Three-Dimensional Imitative Model of Phenomena in One-Dimensional Crystals
Autorzy:: Bercha, D. M.
Sznajder, M.
Bercha, A. I.
Kharkhalis, L. Yu.
Rushchanskii, K.
Tematy:: 71.20.Nr
71.45.-d
63.20.Dj
63.20.Kr
63.22.+m; Pokaż więcej
Wydawca:: Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:: https://bibliotekanauki.pl/articles/1969018.pdf Link otwiera się w nowym oknie
Opis:: For three-dimensional charge carriers described by the dispersion law with quartic terms of the wave vector, the density of states function similar as in the one-dimensional case was determined. This similarity allows the Pekar and Dejgen condenson states in the continuum approximation to exist. The calculated phonon spectrum reveals optical vibrations of a very low frequency, which favours the electron-phonon interaction and creation of the condenson states.
Dostawca treści:: Biblioteka Nauki

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