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1.
In the context of density functional theory, the phonon density of states and phonon dispersion are calculated for ZnGa2Se4. The temperature dependence of the heat capacity of ZnGa2Se4 in the temperature range 5–400 K is obtained. The calculated frequencies and symmetries of phonon modes in the center of the Brillouin zone are in good agreement with experimental data obtained by Raman spectroscopy and infrared spectroscopy. 相似文献
2.
E. M. Sheregii J. Cebulski J. Polit V. I. Ivanov-Omskii W. Gebicki 《Semiconductors》1998,32(8):901-909
The magnetophonon resonance in a multimode crystal of the solid solution ZnxCdyHg1−x−y
Te (x=0.08, y=0.11) was investigated in the temperature interval from 77 to 200 K. To interpret the obtained structure of the magnetophonon
resonance spectrum, the phonon modes of three compositions of this solid solution were studied by the Raman scattering method.
The results presented confirm the three-mode behavior (excluding cluster modes) of the phonon spectrum of the solid solutions
of this class. The complicated structure of the magnetophonon resonance bands is interpreted on the basis of the values obtained
for the phonon frequencies. The characteristic features of electron transport in such a lattice are shown.
Fiz. Tekh. Poluprovodn. 32, 1006–1015 (August 1998) 相似文献
3.
First-principles calculations are performed to investigate dynamical and dielectric properties of group-III-nitrides. We focus
on vibrational frequencies, dynamical charges, and the phonon density of states of cubic AlN, GaN, and InN. Chemical trends
are derived and discussed. The first ab initio calculations of phonon branches and density of states are presented for an
ordered InxGa1−xN structure. 相似文献
4.
The structure, lattice dynamics, and some thermodynamic properties of orthorhombic OsSi2 were investigated using a first-principles density functional theory (DFT). Linear response theory was used to calculate the phonon dispersion relation and phonon density of states for OsSi2 as well as its infrared and Raman active mode frequencies. In this study, the thermodynamic properties, including vibrational entropy (Svib), constant-volume specific heat (Cv), and Debye temperature (ΘD), were predicted theoretically and discussed. 相似文献
5.
The vibrational properties of silicon doped GaN nanowires with diameters comprised between 40 and 100 nm are studied by Raman spectroscopy through excitation with two different wavelengths: 532 and 405 nm. Excitation at 532 nm does not allow the observation of the coupled phonon–plasmon upper mode for the intentionally doped samples. Yet, excitation at 405 nm results in the appearance of a narrow peak at frequencies close to that of the uncoupled A1(LO) mode for all samples. This behavior points to phonon–plasmon scattering mediated by large phonon wave-vector in these thin and highly doped nanowires. 相似文献
6.
Using the method of linear response, vibrational spectra and densities of states of GaP and AlP crystals and monolayer GaP/AlP superlattices are calculated. Phonon modes of (GaP) n (AlP) m superlattices with various numbers of monolayers are calculated for the center of the Brillouin zone. The obtained results are compared with the Raman scattering data and the effect of nonideality of the interface on phonon frequencies is discussed. 相似文献
7.
S. F. Yoon Y. B. Miao K. Radhakrishnan S. Swaminathan 《Journal of Electronic Materials》1996,25(9):1458-1462
Growth of In0.52Al0.48As epilayers on InP (100) substrates by molecular beam epitaxy at different silicon doping levels is carried out. The doped
samples show an inverted S-shaped dependence of the PL peak energy variation with the temperature which weakens at high doping
levels due to a possible reduction in the donor binding energy. There is a reduction in both the AlAs-like and InAs-like longitudinal-optic
(LO) phonon frequencies and a broadening of the LO phonon line shape as the doping level is increased. The PL intensity also
showed in increasing degrees at higher doping levels, a temperature dependence which is characteristic of disordered and amorphous
materials. 相似文献
8.
S. Farjami Shayesteh K. Hidari 《Journal of Infrared, Millimeter and Terahertz Waves》2002,23(10):1455-1464
Infrared Fourier transform spectroscopy has been used to investigate phonon, plasmon, surface polariton and plasma-longitudinal optical phonon coupling in highly donor doped multi quantum wells (GaAs/Al0.33Ga0.67As) and direct band gap n- type AlXGa1-XAs thin layer on GaAs substrate. Using different samples with different concentration of free carriers. The dispersion equation of coupling modes have been calculated by using the condition which the dielectric functions of samples are zero for longitudinal coupled modes and experimental papameters which have been obtained from the best fit p-polarized oblique incidence far infrared reflection spectra. In MQW samples, the free carriers confined to the well and carriers are quasi two dimensional. So, plasmon- LO phonon coupling occur in the well (GaAs). In n- type AlXGa1-XAs thin layer, the coupled modes consist of three branches of the high, intermediate and low frequency modes. Their frequencies depend on both concentration and alloy composition. To analyses the surface polariton modes we carry out attenuated total reflection (ATR) measurements. In order to support our assignment the magnetic field profiles and surface polariton dispersion curves have been calculated. 相似文献
9.
10.
The phonon heat conductivity k
ph in Bi1 − x
Sb
x
(x = 0.04–0.12) alloys is investigated in the temperature range of 6–60 K. The results are compared with the theory of solids
at low temperatures, and the basic sources of phonon scattering are revealed. It is shown that phonon scattering at local
mass changes dominates over other sources. The dependences of k
ph on composition are considered at temperatures of 60 and 90 K, and it is found that the normal N processes substantially affect the phonon scattering under these conditions. The donor-impurity effect on heat conductivity
of Bi0.88Sb0.12 is considered, and the heat resistance caused by the phonon scattering at impurity centers is singled out. 相似文献
11.
Z. A. Dzhakhangirli T. G. Kerimova N. A. Abdullayev I. A. Mamedova N. T. Mamedov 《Semiconductors》2017,51(5):556-558
The density of phonon states and the phonon dispersion in the Brillouin zone are calculated by the density functional method of. The displacements of atoms in the elementary cell are constructed for vibrations of the A, B, and E symmetries. The calculated frequencies of optical phonons are consistent with the experimentally determined frequencies from the IR-absorption (infrared) and Raman-scattering spectra. In the xy plane, the intersection of low-frequency optical phonons with acoustic phonons is observed. 相似文献
12.
Effect of Nanopores on the Phonon Conductivity of Crystalline CoSb3: A Molecular Dynamics Study 总被引:1,自引:0,他引:1
Xu-qiu Yang Peng-cheng Zhai Li-sheng Liu Gang Chen Qing-jie Zhang 《Journal of Electronic Materials》2014,43(6):1842-1846
Molecular dynamics simulations have been performed to investigate the effect of nanometer-size pores on the phonon conductivity of single-crystal bulk CoSb3. The cylindrical pores are uniformly distributed along two vertical principal crystallographic directions of a square lattice. Because pore diameter and porosity are two key factors that could affect the performance of the materials, they were varied individually in the ranges a 0–6a 0 and 0.1–5%, respectively, where a 0 is the lattice constant of CoSb3. The simulation results indicate that the phonon conductivity of nanoporous CoSb3 is significantly lower than that of no-pore CoSb3. The reduction of phonon conductivity in this simulation was consistent with the ballistic–diffusive microscopic effective medium model, demonstrating the ballistic character of phonon transport when the phonon mean-free-path is comparable with or larger than the pore size. Reducing pore diameter or increasing porosity are alternative means of effective reduction of the thermal conductivity of CoSb3. These results are expected to provide a useful basis for the design of high-performance skutterudites. 相似文献
13.
Zone-center optical phonons of tetrahedrally coordinatedII-VI semiconductor ternary (AB1-xCx) and quaternary (AB1-x-yCxDy) alloys display a variety of distinct multi-mode behavior patterns. A brief review of the modified random element isodisplacement
model, which can satisfactorily account for the composition dependence of the frequencies of the zone-center optical phonons,
is presented; in this model, one uses the macroscopic parameters of the binary end members and their LO-TO phonon frequencies.
When a constituent is present in extreme dilution in a binary (or in a ternary), e.g., C in AB (or in AB1-y Dy), one sees either a local or a gap mode associated with it. For higher concentrations, one can see two (three) LO-TO phonon
pairs for the ternary (quaternary) in the first order Raman spectrum or in the infra-red deduced from an analysis of the reststrahlen
bands, when the masses of B and C differ significantly but are lighter than that of A. We illustrate these features in the
Raman spectra of Cd1-xMgxTe and Cd1-x-y MgxMnyTe. Also shown are the infra-red spectra of the local mode of Mg2+ and Mn2+ in Cd Te, where their isotopic nature is clearly manifested. 相似文献
14.
L. K. Vodop’yanov I. V. Kucherenko A. Marchelli E. Burattini M. Piccinini M. Cestelli Guidi R. Tribulet 《Semiconductors》2006,40(1):39-42
The narrow-gap II-VI and IV-VI alloys are convenient objects for studying the electron-phonon interaction. However, the concentration of free carriers in the IV-VI alloys is rather high (~1018 cm?3), which complicates studying this effect, by the optical reflection method. The concentration of free carriers in the narrow-gap Hg1-x ZnxTe alloys is considerably lower (~1016 cm?3). Therefore, the plasma component exerts less effect on the lattice reflection spectrum. The reflection spectra of Hg1-x ZnxTe crystals with x = 0.1–1 were studied in the far-IR region in the range of 30–700 cm?1 at 40–300 K. Using the dispersion analysis and the Kramers-Kronig method, the frequencies of the TO phonons of the HgTe-like and ZnTe-like modes were determined depending on the composition. It is shown that the reconstructed phonon spectrum involves two modes. The temperature dependences of the frequencies of the TO phonons and the damping parameter were measured for the narrow-gap alloy with x = 0.1 in the range of 80–200 K. A decrease in the frequency of the TO phonon of the soft mode in the vicinity of the inversion point of the bands at T = 110 K was for the first time found by optical methods. The damping parameter slightly increases in the vicinity of this temperature. The result obtained qualitatively agreed with the theoretical model of Kawamura et al., which makes allowance for the effect of the electron-phonon interaction on the frequency of the soft mode in the IV-VI compounds. 相似文献
15.
Kenji Kumazaki 《Journal of Infrared, Millimeter and Terahertz Waves》1985,6(8):765-770
Far infrared reflection spectra of CdXHg1?X Se are measured in the region 20 to 600 cm?1 at temperatures between 5 and 77 K. Reflection spectra are explained well by the dynamic dielectric function which is constructed as a sum of Γ8?Γ8 interband, intraband and phonon contributions. The plasmon-LO phonon coupling effect is also discussed. 相似文献
16.
The farinfrared properties of mixed alkalai halide crystals, K1?xRbxI, x=0.25 and 0.50, have been studied at room temperature. Dispersive Fourier transform spectroscopy (DFTS) has been used to obtain the complex dielectric function of these samples. Infrared-active phonon modes are observed at frequencies close to those of KI and RbI. This two-mode behavior is in agreement with theoretical predictions. 相似文献
17.
A. Yangthaisong 《Journal of Electronic Materials》2013,42(6):993-998
Through first-principles pseudopotential calculations based on density functional theory, the electronic structure and lattice vibrational properties of Pbnm orthorhombic SrHfO3 were investigated in the framework of standard functional approximation and density functional perturbation theory, respectively. The calculated equilibrium lattice constants of Pbnm orthorhombic SrHfO3 are in good agreement with available experimental and theoretical results. The results show that Pbnm orthorhombic SrHfO3 is an insulator with a direct band gap of 3.9 eV and 4.0 eV within the calculations using local density approximation (LDA) and generalized gradient approximation (GGA), respectively. Use of the screened exchange local density approximation (sX-LDA) as a functional in a successive band calculation has also been performed. The band gap is predicted to be 6.7 eV within sX-LDA, somewhat higher than the gap values of 6.1 ± 0.1 eV and 6.5 eV obtained from recent x-ray photoelectron spectroscopy. The phonon dispersion curves of Pbnm orthorhombic SrHfO3 were also calculated. All-positive phonon frequencies were observed in the whole Brillouin zone, indicating stability of the Pbnm orthorhombic SrHfO3 structure. In addition, the infrared-active and Raman-active vibrational modes of SrHfO3 were calculated and compared with available theoretical and experimental investigations. 相似文献
18.
J. P. Estrera W. M. Duncan Y. C. Kao H. Y. Liu E. A. Beam 《Journal of Electronic Materials》1991,20(12):983-987
We present a systematic study of In
x
Ga1−x
As on InP grown by molecular beam epitaxy using the characterization techniques of Fourier transform photoluminescence, x-ray
diffraction, micro-Raman spectroscopy, and photoreflectance spectroscopy. The four techniques were used to determine and correlate
the fundamental parameters of band-gap energy, phonon frequency and composition. Comparing room temperature (293 K) PL and
low temperature PL indicate the presence of a partially ionized acceptor with binding energy of about 13 meV in the unintentionally
doped material. Double crystal x-ray diffraction (XRD) using a symmetric <400> and asymmetric <224> reflections was also employed.
The use of two reflections gives precise lattice constants, composition, and extent of film relaxation. Micro-Raman spectroscopy
was used to measure phonon frequencies in the In
x
Ga1−x
As films and correlated to XRD composition. Room temperature photoreflectance (PR) was used to determine band-gap energy for
both the low and intermediate field cases. Band gap energies determined at room temperature by PL and PR were in agreement
within experimental error. 相似文献
19.
Dovletgeldi Seyitliyev Xixi Qin Manoj K. Jana Svenja M. Janke Xiaowei Zhong Wei You David B. Mitzi Volker Blum Kenan Gundogdu 《Advanced functional materials》2023,33(21):2213021
Electron–phonon interactions play an essential role in charge transport and transfer processes in semiconductors. For most structures, tailoring electron–phonon interactions for specific functionality remains elusive. Here, it is shown that, in hybrid perovskites, coherent phonon modes can be used to manipulate charge transfer. In the 2D double perovskite, (AE2T)2AgBiI8 (AE2T: 5,5“-diylbis(amino-ethyl)-(2,2”-(2)thiophene)), the valence band maximum derived from the [Ag0.5Bi0.5I4]2– framework lies in close proximity to the AE2T-derived HOMO level, thereby forming a type-II heterostructure. During transient absorption spectroscopy, pulsed excitation creates sustained coherent phonon modes, which periodically modulate the associated electronic levels. Thus, the energy offset at the organic–inorganic interface also oscillates periodically, providing a unique opportunity for modulation of interfacial charge transfer. Density-functional theory corroborates the mechanism and identifies specific phonon modes as likely drivers of the coherent charge transfer. These observations are a striking example of how electron–phonon interactions can be used to manipulate fundamentally important charge and energy transfer processes in hybrid perovskites. 相似文献
20.
A. Yangthaisong 《Journal of Electronic Materials》2012,41(3):535-539
The electronic structure and lattice vibrational properties of cubic SrHfO3 were investigated by first-principles calculations based on density functional theory in the framework of the local density
approximation (LDA), generalized gradient approximation (GGA), and density functional perturbation theory (DFPT), respectively.
The calculated equilibrium lattice constant of cubic SrHfO3 is in good agreement with available experimental and theoretical results. The results show that cubic SrHfO3 is an insulator with an indirect LDA (GGA) band gap of 3.6 (3.7) eV. Use of the screened exchange local density approximation
(sX-LDA) as a functional in successive band calculation has also been performed. The band gap is predicted to be 6.27 eV within
sX-LDA, in excellent agreement with the gap value of 6.1 ± 0.1 eV obtained from x-ray photoelectron spectroscopy. The phonon
dispersion curves and LO–TO splitting of cubic SrHfO3 were also calculated. Negative phonon frequencies were observed along the M–Γ–R–M line in the Brillouin zone, indicating
instability of the SrHfO3 structure, consistent with previous theoretical investigation. 相似文献