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Tytuł:
Hot Phonons in a Biased Two-Dimensional InGaAs Channel
Autorzy:
Aninkevičius, V.
Liberis, J.
Matulionis, A.
Matulionienė, I.
Powiązania:
https://bibliotekanauki.pl/articles/1818476.pdf
Data publikacji:
2005-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
72.20.Ht
Opis:
Experimental dependence of microwave noise temperature on supplied electric power is used to estimate hot-phonon number in a modulation-doped In_{0.52}Al_{0.48}As/In_{0.53}Ga_{0.47}As/In_{0.7} Ga_{0.3}As/In_{0.52}Al_{0.48}As two-dimensional electron gas channel (n_{2D}=2.3×10^{12} cm^{-2}). The nonequilibrium occupancy of the involved longitudinal optical phonon states exceeds the equilibrium one nearly twice at 2 kV/cm electric field. test
Źródło:
Acta Physica Polonica A; 2005, 107, 2; 304-309
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scattering of Excitons by Phonons in Quantum Wells
Autorzy:
Bardyszewski, W.
Prywata, M.
Powiązania:
https://bibliotekanauki.pl/articles/1947245.pdf
Data publikacji:
1996-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.Dx
71.38.+i
72.80.Ey
Opis:
A method to describe the effects of the exciton-optical phonon interaction is presented using the cumulant expansion approximation. The functional-integral technique of coherent phonon states is used in order to justify the commonly used model Hamiltonian and generate the proper perturbation series. The influence of the mutual electron-hole screening on the polaronic effects in quantum wells is analyzed.
Źródło:
Acta Physica Polonica A; 1996, 90, 4; 715-718
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Transient Response of Electrons and Phonons in ZnTe Crystals
Autorzy:
Brazis, R.
Raguotis, R.
Powiązania:
https://bibliotekanauki.pl/articles/1813220.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.Di
72.20.Ht
72.15.Lh
78.45.+h
Opis:
The response of electron and phonon ensemble to the switching on and off electric field E in n-type ZnTe crystals is simulated by Monte Carlo method. The results at T=10 K show significant accumulation of LO-phonons and the LO phonon band population inversion with respect to the LA band;the inversion is necessary for the stimulated transfer of LO-LA energy difference to photons. The maximum inversion is at E=7 kV/cm. At T=300 K no phonon band inversion but fast (sub-picosecond) drift velocity switching with ≈100 GHz repetition is feasible.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 933-936
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Infrared active phonons and optical band gap in multiferroic GdMnO₃ studied by infrared and UV-visible spectroscopy
Autorzy:
Bukhari, S.
Ahmad, J.
Powiązania:
https://bibliotekanauki.pl/articles/1075504.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.-e
78.20.-e
72.20.-i
73.20.Mf
Opis:
Optical properties of multiferroic GdMnO₃ synthesized by sol-gel method have been investigated by measuring the infrared reflectivity and UV-visible absorption spectra. The infrared reflectivity spectrum of polycrystalline GdMnO₃ in the frequency range 30-7500 cm^{-1} at room temperature contains several phonon modes. The resonant frequency of observed infrared active phonon modes is found comparable with theoretically predicted results. Mean Born effective charges are calculated and discussed in view of the origin of ferroelectricity in GdMnO₃. Three strong absorption peaks observed in the UV-visible spectrum are attributed to the Mn (3d)-electron transitions. The optical band gap ≈1.2 eV is estimated from UV-visible absorption spectrum using Tauc's relation. GdMnO₃ seems to behave like an indirect gap semiconductor.
Źródło:
Acta Physica Polonica A; 2016, 129, 1; 43-48
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Phonons in Adsorbates
Autorzy:
Dobrzynski, L.
Djafari Rouhani, B.
Zieliński, P.
Akjouj, A.
Sylla, B.
Oumghar, E.
Powiązania:
https://bibliotekanauki.pl/articles/1943987.pdf
Data publikacji:
1996-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.35.JS
68.45.-v
Opis:
After a brief review on surface phonons, we focus on resonant phonons in adsorbed thin layers. Such resonances may in general be understood within the substrate bulk band as thin layer modes shiften and broaden by the interaction with the substrate phonons. These resonant phonons appear as well-defined peaks in the phonon density of states. Their experimental study started recently by Helium atom scattering spectroscopy. This review will end by a prospective revue done mostly after the presentation of two unpublished results. First the slab resonant phonons may almost be confined in the surface slab even for frequencies falling within the bulk phonon band, if the surface slab is separated from the substrate by a buffer layer. The other prospective unpublished result deals with a model system in which the propagating phonons reach a space point from which they can continue to propagate through two different finite in space channels before reaching again a homogeneous uniform path. Such a system exhibits some frequencies for which the transmission factor vanishes. This phenomenon is related to the resonances associated with the finite additional path offered to the propagation of the phonons.
Źródło:
Acta Physica Polonica A; 1996, 89, 2; 139-144
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonant Phonons in Adsorbed Slabs
Autorzy:
Dobrzynski, L.
Akjouj, A.
Syla, B.
Djafari-Rouhani, B.
Powiązania:
https://bibliotekanauki.pl/articles/1892256.pdf
Data publikacji:
1992-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
68.60.-p
Opis:
Resonant phonons, sometimes also called leaky waves, are phonons associated with a crystal defect, a surface, an adsorbed layer and whose frequencies fall inside the bulk crystal band. Such resonant phonons were studied experimentally and theoretically before for clean surfaces and for adsorbed monolayers. We present here a study of resonant phonons associated with the adsorption of a slab of L monolayers on a substrate. With the help of a simple atomic model, we obtained a closed form expression giving the variation of the transverse phonon density of states associated with the adsorption of the slab. An application which qualitatively simulates the adsorption of L monolayers of Ge on Si shows the existence of well-defined resonant phonons within the bulk acoustic band of the substrate.
Źródło:
Acta Physica Polonica A; 1992, 81, 1; 85-90
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Stabilized 1D Metal in TTF(Ni(dmit)$\text{}_{2}$)$\text{}_{2}$ through Very Weak Coupling between Phonons and Weakly Correlated Fermions
Autorzy:
Doublet, M. L.
Malfant, I.
Hebrard, S.
Canadell, E.
Gaultier, J.
Chasseau, D.
Legros, J. P.
Brossard, L.
Powiązania:
https://bibliotekanauki.pl/articles/1933351.pdf
Data publikacji:
1995-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Hk
71.45.Lr
61.66.Hq
Opis:
Extended Hückel band structure calculations derived from low temperature X-ray structural data, provide evidence, as temperature decreases, for an increasing 1D character of the multiparallel bands of the TTF(Ni(dmit)$\text{}_{2}$)$\text{}_{2}$ compound. This result is discussed within the monotonous metallic behaviour of the weakly correlated fermions gas, despite condensations of charge density wave instabilities.
Źródło:
Acta Physica Polonica A; 1995, 87, 4-5; 781-784
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Phonons in HgCdMnTe Using Far-Infrared Reflectivity
Autorzy:
Dudziak, E.
Bożym, J.
Pruchnik, D.
Baran, J.
Powiązania:
https://bibliotekanauki.pl/articles/1929684.pdf
Data publikacji:
1993-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.30.Fs
71.45.Gm
Opis:
The first reflectivity spectra of Hg$\text{}_{1-x-y}$Cd$\text{}_{x}$Mn$\text{}_{y}$Te with 0.03 < x < 0.1 and 0 < y < 0.05 were measured in the spectral region 700-30 cm$\text{}^{-1}$ at 300 K and 90 K. The quaternary alloys measured show three mode behaviour. The experimental results are interpreted by using a classical dynamic dielectric function model.
Źródło:
Acta Physica Polonica A; 1993, 84, 3; 595-598
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Piezospectroscopy of Phonons in Bulk 6H-SiC
Autorzy:
Grodecki, K.
Wysmołek, A.
Stępniewski, R.
Baranowski, J.
Hofman, W.
Tymicki, E.
Grasza, K.
Powiązania:
https://bibliotekanauki.pl/articles/1791360.pdf
Data publikacji:
2009-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
62.50.-p
42.65.Dr
63.20.-e
78.30.-j
Opis:
Raman piezospectroscopy of high quality 6H-SiC crystals is presented. The crystals used in experiments were grown by the seeded physical vapor transport method. Uniaxial stress up to 0.9 MPa, obtained using a spring apparatus, was applied along [11-20] and [10-10] directions. It was found that the application of uniaxial stress led to different energy shifts of the observed phonon excitations in the investigated 6H-SiC crystals. The obtained pressure coefficients vary in the range 0.98-5.5 $cm^{-1}$ $GPa^{-1}$ for different transverse optical phonon modes. For longitudinal optic phonon modes pressure coefficients in the range 1.6-3.6 $cm^{-1}$ $GPa^{-1}$ were found. The data obtained could be useful in evaluation of local strain fields in SiC based structures and devices including epitaxial graphene.
Źródło:
Acta Physica Polonica A; 2009, 116, 5; 947-949
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Excitons and Phonons in GaN. Magnetooptical and Spatially Resolved Investigations
Autorzy:
Hoffmann, A.
Eckey, L.
Siegle, H.
Kaschner, A.
Christen, J.
Bertram, F.
Liu, Q. K. K.
Powiązania:
https://bibliotekanauki.pl/articles/1968986.pdf
Data publikacji:
1998-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.35.-y
78.40.Fy
78.45.+h
Opis:
A comprehensive study of the direct photoluminescence from free-exciton states in GaN using polarization-dependent and magnetooptical measurements is presented. We measured and identified fine-structure splittings in the n=1 state of the A-exciton. From the magnetoluminescence data obtained in fields up to 15 T we determined the g-values of the conduction and valence bands parallel and perpendicular to the c-axis. Self-organized hexagonal GaN pyramids of 5 μm width and covered by six {11̲01} side facets were investigated by spatially resolved cathodoluminescence and micro-Raman spectroscopy. Beside a narrow luminescence peak at 355 nm, originating from the 2 μm thick GaN layer, an additional broad luminescence band was observed from the GaN pyramids around a wavelength of 357 nm. A strong energy shift is found along the {11̲01} pyramidal facets and directly visualized by monochromatic cathodoluminescence images and line scans. In GaN epilayers grown on GaAs substrates a series of sharp modes in the range between 60 cm$\text{}^{-1}$ and 250 cm$\text{}^{-1}$ for temperatures below 100 K was found. The intensities of these modes increased drastically with decreasing temperature. Raman excitation spectra showed a maximum between 514.5 nm and 568 nm. A comparison of spatially resolved investigations with that of intentionally doped GaN epilayers showed that the in-diffusion of As from the substrate plays an important role. Raman spectra as a function of external fields, like magnetic field and hydrostatic pressure, gave additional information about the defect type and the underlying scattering mechanism.
Źródło:
Acta Physica Polonica A; 1998, 94, 2; 125-137
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phonon-Induced Thermodynamic Properties of Ultra-narrow Wires
Autorzy:
Ilić, D.
Šetrajčić, J.
Jaćimovski, S.
Powiązania:
https://bibliotekanauki.pl/articles/1029824.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
Phonons
ultra-narrow wire
the Green function
thermodynamics
specific heat
Opis:
In this paper, we investigated the influence of size effect on thermodynamic properties of ultra-narrow wires with a simple cubic lattice, by means of two-time dependent Green functions method, adjusted to confined crystalline structures. Poles of Green functions, which defining phonon spectra, are found by solving the secular equation. For different boundary parameters, this problem is presented graphically. The temperature behavior of ultra-narrow wire thermal capacitance is compared to that of bulk structures. It turned out that in low-temperature region thermal capacitance of the ultra-narrow wire is notably lower than in the corresponding bulk sample. How this fact reflects the thermal, conducting and superconducting properties of materials, is discussed in the conclusion.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 57-62
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Acoustic Phonons on the Magnetic Anisotropy in GaMnAs Magnetic Semiconductors
Autorzy:
Jasiukiewicz, C.
Stagraczyński, S.
Lehmann, D.
Dugaev, V.
Berakdar, J.
Powiązania:
https://bibliotekanauki.pl/articles/1402566.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.50.Pp
75.30.Gw
77.80.Fm
Opis:
We present a theoretical description of the influence of incoherent acoustic phonons on the magnetic anisotropy of magnetic semiconductors. Our theory is based on the six-band Kane model of the electron energy spectrum describing the valence band with k· p Hamiltonian including the hole-phonon interaction term. We include the effect of incoherent phonons through the hole self-energy in the six-band model, and assume a strong laser-pulse-induced flux of non-equilibrium acoustic phonons. The results of numerical calculations of magnetic anisotropy performed for (GaMn)(AsP) magnetic alloy semiconductors demonstrate the essential role of incoherent phonons.
Źródło:
Acta Physica Polonica A; 2015, 128, 2; 179-181
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Images of the Response Signal of a 2D Gas of Carriers to a Pulsed Beam of 3D Phonons
Autorzy:
Jasiukiewicz, Cz.
Lehmann, D.
Paszkiewicz, T.
Powiązania:
https://bibliotekanauki.pl/articles/1929698.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
66.70.+f
73.40.Lq
Opis:
The patterns for the time integrated drag current induced by a pulsed beam of bulk phonons in a 2D gas of charge carriers are calculated. A beam of Planckian phonons propagates in a GaAs crystal. We considered a 2D gas of electrons lying in a {001} plane and a 2D gas of holes lying in the {311} plane. Planckian phonons are radiated by an extended (Gaussian) source.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 661-664
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Raman Scattering from Acoustic Phonons Confined in Spherical Nanoparticles
Autorzy:
Kostić, R.
Powiązania:
https://bibliotekanauki.pl/articles/1807815.pdf
Data publikacji:
2009-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.46.Df
63.22.-m
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.
Źródło:
Acta Physica Polonica A; 2009, 116, 1; 62-64
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Observation of Second-Generation Nonequilibrium Phonons in Highly Photoexcited CdS Microcrystals
Autorzy:
Kurilc̆ik, G.
Strumskis, M.
Jurs̆ėnas, S.
Z̆ukauskas, A.
Powiązania:
https://bibliotekanauki.pl/articles/1952036.pdf
Data publikacji:
1996-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
63.20.Kr
78.47.+p
78.55.Et
Opis:
Luminescence kinetics of nonthermalized electron-hole plasma in highly excited CdS microcrystals embedded in glass was studied at T=295 K using two pump pulses technique. The observed carrier kinetics shows additional increase in the effective temperature during the pump pulse as a result of the prepump pulse. The increase is shown to be produced by a fusion of long-lived second-generation nonequilibrium phonons generated by the prepump pulse. The experimental results are in good agreement with a model of hot electron-hole plasma energy relaxation with a build-up of two generations of nonequilibrium phonons.
Źródło:
Acta Physica Polonica A; 1996, 90, 5; 875-878
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 25

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