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1.
S.K. Biswas A.R. Ghatak A. Neogi A. Sharma S. Bhattacharya K.P. Ghatak 《Physica E: Low-dimensional Systems and Nanostructures》2007,36(2):163-177
We study theoretically the thermoelectric power in the presence of a large magnetic field (TPM) in heavily doped III–V, II–VI, PbTe/PbSnTe, strained layer and HgTe/CdTe quantum dot superlattices (QDSLs) with graded structures on the basis of newly formulated electron energy spectra and compare the same with that of the constituent materials. It has been found, taking heavily doped GaAs/Ga1−xAlxAs, CdS/CdTe, PbTe/PbSnTe, InAs/GaSb and HgTe/CdTe QDSLs as examples, that the TPM increases with increasing inverse electron concentration and film thickness, respectively, in different oscillatory manners and the nature of oscillations is totally band structure dependent. We have also suggested the experimental methods of determining the Einstein relation for the diffusivity–mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws. 相似文献
2.
K. P. Ghatak 《Il Nuovo Cimento D》1991,13(10):1321-1324
Summary An attempt is made to formulate the thermoelectric power under strong magnetic quantization (TPM) in superlattices (SLS) of
III–V semiconductors with graded structures and to compare the same with that of the forming materials. It is found, taking
Ga0.8In0.14P0.78Sb0.22/GaAs SL as an example, that the TPM increases with increasing quantizing magnetic field and decreases with increasing electron
concentration respectively in an oscillatory manner. The TPM in SL with graded structures is greater than that of the constituent
bulk materials for III–V SL. 相似文献
3.
Influence of quantum confinement on the photoemission from superlattices of optoelectronic materials
D. De A. Kumar S.M. Adhikari S. Pahari N. Islam P. Banerjee S.K. Biswas S. Bhattacharya K.P. Ghatak 《Superlattices and Microstructures》2010
We study the photoemission from quantum wire and quantum dot superlattices with graded interfaces of optoelectronic materials on the basis of newly formulated electron dispersion relations in the presence of external photo-excitation. Besides, the influence of a magnetic field on the photoemission from the aforementioned superlattices together with quantum well superlattices in the presence of a quantizing magnetic field has also been studied in this context. It has been observed taking into account HgTe/Hg1−xCdxTe and InxGa1−xAs/InP that the photoemission from these nanostructures increases with increasing photon energy in quantized steps and exhibits oscillatory dependences with the increase in carrier concentration. Besides, the photoemission decreases with increasing light intensity and wavelength, together with the fact that said emission decreases with increasing thickness exhibiting oscillatory spikes. The strong dependences of the photoemission on the light intensity reflects the direct signature of light waves on the carrier energy spectra. The content of this paper finds six applications in the fields of low dimensional systems in general. 相似文献
4.
Structural, electronic, optical and magnetooptical investigations on compositional superlattices (mainly PbTe/PbSnTe, PbTe/PbEuSeTe) are summarized. Recent results on transport and magnetooptical effects in PbTe doping superlattices are presented and examples for an excellent photoconductivity response of these structures in the 5μm region are given. 相似文献
5.
6.
Summary An attempt is made to study the effective electron mass in quaternary alloys, taking a In1−x
Ga
x
As
y
P1−y
lattice matched to InP, by using the three-band Kane model under different physical conditions,e.g. bulk specimens, magnetic quantization, cross-field configuration, quantum well, electric-field-aided quantum well, magnetic-field-aided
quantum well, quantum well under cross fields, quantum well wires, electric-field-aided quantum well wires, magnetic-field-aided
quantum well wires and quantum well wires under cross fields by formulating the respective expressions. We have plotted the
effective Fermi level mass with various physical variables under different conditions. In the presence of a quantizing magnetic
field the effective mass depends on the spin splitting of Landau levels due to the spin-orbit splitting parameter of the valence
bands. Under cross-field configuration and the various quantum confined low-dimensional systems, the effective masses depend
on the respective quantum numbers in addition to the Fermi energies even for parabolic models because of the inherent features
of such systems. In addition, the corresponding results for relatively wide-gap materials have also been obtained from our
generalized formulations under certain limiting conditions. 相似文献
7.
K.P. Ghatak S. Bhattacharya S. Pahari D. De R. Benedictus 《Superlattices and Microstructures》2009,46(3):387-414
We investigate the Einstein relation for the diffusivity-mobility ratio (DMR) for n-i-p-i and the microstructures of nonlinear optical compounds on the basis of a newly formulated electron dispersion law. The corresponding results for III-V, ternary and quaternary materials form a special case of our generalized analysis. The respective DMRs for II-VI, IV-VI and stressed materials have been studied. It has been found that taking CdGeAs2, Cd3As2, InAs, InSb, Hg1−xCdxTe, In1−xGaxAsyP1−y lattices matched to InP, CdS, PbTe, PbSnTe and Pb1−xSnxSe and stressed InSb as examples that the DMR increases with increasing electron concentration in various manners with different numerical magnitudes which reflect the different signatures of the n-i-p-i systems and the corresponding microstructures. We have suggested an experimental method of determining the DMR in this case and the present simplified analysis is in agreement with the suggested relationship. In addition, our results find three applications in the field of quantum effect devices. 相似文献
8.
S. Muensit P. Sukwisut P. Khaenamkeaw S. B. Lang 《Applied Physics A: Materials Science & Processing》2008,92(3):659-663
Sol–gel techniques were used to prepare thin films of Pb(Zr
x
,Ti1−x
)O3 (PZT) with three different Zr/Ti ratios and a graded PZT film with three different compositional layers. A Michelson interferometer
was used to measure the thickness strains due to an applied ac electric field. Effective d
33 piezoelectric strain coefficients were computed from the experimental data. Interfacial pinning caused these coefficients
to differ from the true ones. They were corrected for the pinning using both an analytical model and finite-element analysis.
The corrected coefficients of the PZT (52/48) sample were in excellent agreement with values of bulk materials. The coefficients
of the multilayer sample were very low, probably due to insufficient poling or domain switching. 相似文献
9.
V. A. Kutasov L. N. Luk’yanova P. P. Konstantinov G. T. Alekseeva 《Physics of the Solid State》1997,39(3):419-422
A study has been made of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x
Sex solid solutions (x=0.3 and 0.36) in the temperature range 80–300 K. The lowest carrier concentrations, (0.8–1)×1018 cm−3, were obtained by displacing the solid solution from the stoichiometric to a Te-rich composition. At such carrier concentrations,
the second subband in the conduction band of n-Bi2Te3−x
Sex is not filled, which results in a growth of mobility because of the absence of interband scattering, and brings about an
increase of thermoelectric efficiency in the 80–120-K range.
Fiz. Tverd. Tela (St. Petersburg) 39, 483–487 (March 1997) 相似文献
10.
The dc electrical resistivity and magnetoresistivity of polycrystalline manganites La1−x
CaxMnO3 (x=0–0.3) are investigated as functions of the temperature, magnetic field and electric field, along with the microwave surface
resistance. The investigations show that the dc electrical resistivity and magnetoresistivity are governed by the surface
properties of the intergranular boundaries. The dc electrical resistivity is observed to decrease substantially (tenfold)
for a comparatively small electric field (E⋟100 V/cm). Estimates are obtained for the internal electrical resistivity of the granules, the thickness of the contact layer
(which depends on the temperature and the magnetic field), and the height of the potential barrier between the interfaces
separating the surface layer and inner layer of a granule.
Fiz. Tverd. Tela (St. Petersburg) 40, 1881–1884 (October 1998) 相似文献
11.
A study is reported of the thermoelectric and galvanomagnetic properties of n-Bi2Te3−x−y
SexSey solid solutions for 0.12⩽x⩽0.36 and 0.12⩽y⩽0.21 within the 80–300 K temperature region. The thermoelectric figure-of-merit Z has been found to correlate with the parameters of the many-valley energy-band model including anisotropic carrier scattering.
It is shown that a decrease in the constant-energy surface anisotropy and scattering anisotropy results in a growth of Z for optimum carrier concentrations in the solid solution.
Fiz. Tverd. Tela (St. Petersburg) 41, 187–192 (February 1999) 相似文献
12.
N. S. Popovich 《Czechoslovak Journal of Physics》2005,55(6):739-748
High efficiency of thermoelectric conversion can be achieved by using materials with a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Mass-difference-scattering of the phonons is one of the most effective way for reducing the thermal conductivity in bulk thermoelectric materials. Investigations of transport phenomena in (TlBiS2)1-x
(2PbS)x alloys system have shown that in solid solutions of the (A3B5C
2
6
)1-x
(2A4B6)x type at cation substitution according to scheme 2A4(+2) A 3(+1) + B5(+3) occurs a strong decrease of the lattice thermal conductivity. In the vicinity of x = 0. 50 the lattice part of thermal conductivity of (TlBiS2)1-x
(2PbS)x alloys decreases down to 0. 26 W/mK, i. e., it approaches the theoretical minimum. As a result, the thermoelectric figure of merit for these alloys ( 25%) exceeds the respective value for lead sulfide at room temperature. 相似文献
13.
The concentration dependences of the electronic properties (residual electrical resistivity, diffusion thermoelectric power,
normal Hall effect, and low-temperature specific heat) and the magnetic characteristics (magnetization and paramagnetic susceptibility)
of quasibinary (PdxPt1−x
)3Fe, Pt3MnxFe1−x
, (PdxAu1−x
)3Fe, and ScxTi1−x
Fe2 alloys are investigated. A relationship is established between the anomalous behavior of the kinetic properties and the variation
of the local magnetic moments. The absence of corresponding anomalies in the concentration dependence of the specific heat
indicates that the density of states at the Fermi level does not change significantly and, therefore, that the conventional
Mott two-band model cannot be used to describe the anomalies in the properties of the alloys in question. A single interpretation
of the sum-total of the experimental results is given on the basis of the theory of local fluctuations of the electron spin
density in metal magnets.
Fiz. Tverd. Tela (St. Petersburg) 39, 1257–1262 (July 1997) 相似文献
14.
A. B. Granovskii M. V. Kuz’michev J. P. Clerc 《Journal of Experimental and Theoretical Physics》1999,89(5):955-959
The features of the optical and magnetooptical properties of granular alloys with giant magnetoresistance in the IR region
are examined in reference to the magnetorefractive effect and the equatorial Kerr effect. Calculations are performed within
the semiclassical approximation with consideration of spin-dependent scattering in the bulk of the granules and on their surfaces
(interfaces). The expressions obtained for σ
xx(ω) and σ
xy(ω) are found to be sensitive to scattering on the surfaces and in the bulk of the granules, as well as to granule size, the
type of impurities trapped on the interfaces, the frequency of the incident light, and the external magnetic field. For granular
thin films exhibiting giant magnetoresistance, the theory predicts significant relative changes in the optical reflection
and transmission coefficients when the sample is magnetized to saturation (0.02% and 20%, respectively, for giant magnetoresistance
of the order of 20%), as well as Kerr and Faraday effects that are nonlinear with respect to magnetization.
Zh. éksp. Teor. Fiz. 116, 1762–1769 (November 1999) 相似文献
15.
《Current Applied Physics》2020,20(9):1008-1012
Among the intermediate temperature (500–900 K) thermoelectric materials, both the p- and n-type lead telluride (PbTe) compounds have attracted extensive interests. Till date various approaches were adopted to enhance the thermoelectric performance of n-type PbTe-based materials as they show greater potential space for further improvement compared to p-type ones. Herein, a pseudo-ternary n-type (PbTe)0.95-x(Sb2Se3)x(PbS)0.05 system was designed and a large value of ZT = 1.61 at 850 K in case of x = 0.01 was achieved. Two factors are responsible for the improved thermoelectric performance. The incorporation of lead sulfide is the key factor to maintain a high level of power factor above 700 K and the multi-scale hierarchical architectures yield ultra-low thermal conductivity. 相似文献
16.
Yang Wang Yu Sui Jinguang Cheng Xianjie Wang Wenhui Su Hongjin Fan 《Applied Physics A: Materials Science & Processing》2010,99(2):451-458
The high-temperature transport and thermoelectric characteristics of Ca3−x
Y
x
Co4O9 (x=0–0.75) series were studied up to 1000 K. The results reveal that the substitution of Y3+ for Ca2+ not only increases resistivity but also gradually alters the transport mechanism. The localization of carriers narrows bandwidth,
which induces the evolution of the system from metal to variable-range hopping semiconductor and then to thermally activated
semiconductor. The increasing thermopower with doping originates from the reduction of carrier concentration along with enhanced
electronic correlations. Thermoelectric figure of merit ZT of Ca3Co4O9 system is improved by Y doping. However, the optimal thermoelectric performance is found to only exist at the critical doping
level where doping-induced metal–semiconductor transition occurs. This result suggests an intrinsic correlation between transport
mechanism and thermoelectric response in this system. 相似文献
17.
E. Popova H. Ndilimabaka B. Warot-Fonrose M. Bibes N. Keller B. Berini F. Jomard K. Bouzehouane Y. Dumont 《Applied Physics A: Materials Science & Processing》2008,93(3):669-674
The understanding and control of the ilmenite–hematite solid solutions (Fe2−x
Ti
x
O3±δ
or IH) thin film structure and properties are crucial for spintronics applications. Good quality films of Fe2−x
Ti
x
O3±δ
on Al2O3(0001) substrates were obtained by pulsed laser deposition. For the studied compositions (x=1, 0.7, 0.5) in a wide oxygen pressure range all the films were epitaxial, with flat interfaces, and without secondary phases.
Unconventional lattice strain relaxation with the increase of in-plane lattice parameter above its relaxed bulk value was
observed for different film compositions, oxygen pressures, substrate temperatures, and film growth rates. This phenomenon
is most likely explained by the buckling of a few first film monolayers because of a significant compressive stress induced
on the film by the sapphire substrate. The IH thin films with x=0.7 and 0.5 exhibited the properties of a room temperature magnetic semiconductor. The resistivity changed over three orders
of magnitude in the studied pressure range, thus clearly demonstrating the important role of oxygen stoichiometry in the creation
of carriers. 相似文献
18.
Summary The free convection in the melt during the crystal growth of small-gap semiconductors, and its influence on the electrical
properties are discussed. Dimensionaless parameters of the fluid flow, electrical properties of PbTe, Pb1−x
Sn
x
Te and Hg1−x
Cd
x
Te single crystals, grown by vertical Bridgman technique at very low velocity, and some structures, found in these materials,
support the presence of free convection. 相似文献
19.
Polycrystalline MgxAl2xLi0.5(1−x)Fe2.5(1−x) O4 (x = 0.0, 0.2, 0.5, 0.6 and 0.7) ferrites were prepared by standard ceramic method, and characterized by X-ray diffraction and
infrared absorption spectroscopy. The spectra show two significant absorption bands in the wave number range of 400–1000 cm−1 arising from interatomic vibrations in the tetrahedral and octahedral coordination compounds. The decrease in intensity and
increase in broadness of bands with concentration (x) are explained on the basis of cation distribution. The force constants and bulk modulus are found to decrease with Mg-Al
content (x) which suggested weakening of interatomic bonding. An alternate method for the determination of bulk modulus, longitudinal
and transverse velocities is suggested. The magnetic and electrical properties of these compounds are explained in the light
of structural and optical properties. 相似文献
20.
Spin resonances of the third-order non-linear susceptibility of epitaxial layers of n- and p-type Pb1?xSnxTe and Pb1?xSnxTe/PbTe superlatttices have been observed by four photon mixing of the radiation of two CO2-lasers. Precise data on the effective g-values of the electrons and holes of Pb1?xSnxTe were obtained. These data and the results of magneto-optical interband absorption measurements are used to obtain k·p parameters within the Mitchell and Wallis band model. In the Pb1?xSnxTe/PbTe superlattices, the same g-values for electrons as in the Pb1?xSnxTe films with the same composition x are found. Consequently, the electrons in the superlattices are confined within the Pb1?xSnxTe layers. Therefore the Pb1?xSnxTe/PbTe system forms a type I and not a staggered superlattice. 相似文献