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1.
The present paper reports the DC conductivity measurements at high electric fields in vacuum evaporated amorphous thin films
of a-Se100−x
Sn
x
(x = 0, 2, 4, 6) glassy alloys. Current-voltage (I–V) characteristics have been measured at various fixed temperatures. In these samples, at low electric fields, ohmic behaviour
is observed. However, at high electric fields (E ∼ 104 V/cm), non-ohmic behaviour is observed. An analysis of the experimental data confirms the presence of space charge limited
conduction (SCLC) in the glassy materials studied in the present case. From the fitting of the data to the theory of SCLC,
the density of defect states (DOS) near Fermi level is calculated. Increase in DOS with increase in Sn concentration has been
found which could be correlated with the electronegativity difference between the two elements used here in making the glassy
alloys. The peculiar role of the element Sn as an impurity in the pure Se glassy alloy is also discussed.
相似文献
2.
Y. Xiao Y. Su C. M. N. Kumar C. Ritter R. Mittal S. Price J. Perßon Th. Brückel 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(2):113-121
The physical and structural properties of Fe1.11Te and
Fe1.11Te0.5Se0.5 have been investigated by means of
X-ray and neutron diffraction as well as physical property
measurements. For the Fe1.11Te compound, the structure
distortion from a tetragonal to monoclinic phase takes place at 64 K
accompanied with the onset of antiferromagnetic order upon cooling.
The magnetic structure of the monoclinic phase was confirmed to be
of antiferromagnetic configuration with a propagation vector
k = (1/2, 0, 1/2) based on Rietveld refinement of neutron
powder diffraction data. The structural/magnetic transitions are
also clearly visible in magnetic, electronic and thermodynamic
measurements. For superconducting Fe1.11Te0.5Se0.5
compound, the superconducting transition with T
c
= 13.4 K
is observed in the resistivity and ac susceptibility measurements.
The upper critical field H
c2 is obtained by measuring
the resistivity under different magnetic fields. The Kim’s critical
state model is adopted to analyze the temperature dependence of the
ac susceptibility and the intergranular critical current density is
calculated as a function of both field amplitude and temperature.
Neutron diffraction results show that
Fe1.11Te0.5Se0.5 crystalizes in tetragonal structure
at 300 K as in the parent compound Fe1.11Te and no structural
distortion is detected upon cooling to 2 K. However an anisotropic
thermal expansion anomaly is observed around 100 K. 相似文献
3.
Thin films of CdSxTe1-x were deposited by the pulse electrodeposition technique using cadmium sulfate, sodium thiosulfate, and tellurium dioxide
on titanium and conducting glass substrates. Structural studies indicated the formation of polycrystalline films possessing
hexagonal structure. The resistivity varies from 53 Ω cm to 8 Ω cm as the stochiometric coefficient “x” value decreases from 1 to 0. The carrier concentration increases with CdTe concentration. It is observed that as the post-heat
treatment temperature increases, the photosensitivity also increases. It is observed that a post-heat treatment temperature
of 550 °C results in high photosensitivity as well as low light resistance. The optical constants, refractive index (n) and extinction coefficient (k) were evaluated from the transmission spectra of the films of different composition. 相似文献
4.
D. Mourad G. Czycholl 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(4):497-507
Zero-dimensional nanocrystals, as obtained by chemical synthesis, offer a broad range of applications, as their spectrum and
thus their excitation gap can be tailored by variation of their size. Additionally, nanocrystals of the type A
x
B1-
x
C can be realized by alloying of two pure compound semiconductor materials AC and BC, which allows for a continuous tuning
of their absorption and emission spectrum with the concentration x. We use the single-particle energies and wave functions calculated
from a multiband sp
3 empirical tight-binding model in combination with the configuration
interaction scheme to calculate the optical properties of
Cd
x
Zn1-
x
Se nanocrystals with a spherical shape. In contrast to common mean-field approaches like the virtual crystal approximation
(VCA), we treat the disorder on a microscopic level by taking into account a finite number of realizations for each size and
concentration.
We then compare the results for the optical properties with recent experimental data and calculate the optical bowing coefficient
for further sizes. 相似文献
5.
For a given crystal structure, say body-centred-cubic, the many-body Hamiltonian H in which nuclear and electron motions are to be treated from the outset on the same footing, has parameters, for the elements, which can be classified as (i) atomic mass M, (ii) atomic number Z, characterizing the external potential in which electrons move, and (iii) bcc lattice spacing, or equivalently one can utilize atomic volume,
. Since the thermodynamic quantities can be determined from H, we conclude that T
c
, the superconducting transition temperature, when it is non-zero, may be formally expressed as T
c
=
. One piece of evidence in support is that, in an atomic number vs. atomic volume graph, the superconducting elements lie in a well defined region. Two other relevant points are that (a) T
c
is related by BCS theory, though not simply, to the Debye temperature, which in turn is calculable from the elastic constants C
11, C
12, and C
44, the atomic weight and the atomic volume, and (b) T
c
for five bcc transition metals is linear in the Cauchy deviation C
* = (C
12 - C
44 )/(C
12 + C
44 ). Finally, via elastic constants, mass density and atomic volume, a correlation between C
* and the Debye temperature is established for the five bcc transition elements.Received: 13 May 2004, Published online: 23 July 2004PACS:
74.62.-c Transition temperature variations - 74.70.Ad Metals; alloys and binary compounds 相似文献
6.
R. Khordad 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):399-403
In this work, the diamagnetic susceptibility and the bindingenergy of a hydrogenic donor impurity both in the parabolic andnon-parabolic conduction band models have been calculated withinthe effective mass approximation for a V-grooveGaAs/Ga1- x Al x As quantum wire. According to the resultsobtained from the present work reveals that (i) the value ofdiamagnetic susceptibility due to the non-parabolicity effect ishigher than that of parabolicity effect; (ii) the values ofdiamagnetic susceptibility and binding energy due to thenon-parabolicity effect is not appreciable at low Al molefractions; (iii) the diamagnetic susceptibility approaches to thebulk value both in L \(\rightarrow\) 0 or L \(\rightarrow\) ∞; (iv)the effect of non-parabolocity is not appreciable in the bindingenergy and energy dependent effective mass, for energies lowerthan 50 MeV. 相似文献
7.
The hierarchical structure of fermion masses of the Standard Model is explained in split fermion models by localizing the
fermions at different points in an extra dimension. We consider split fermion models with two bulk scalars compactified on an orbifold. In the static case we find analytical expression for the localizer. We also address the issue of stability of the localizer.
We also find exact solutions for the fermion zero modes. We explore the parameter space of the model. We find ample opportunity
for construction of phenomenologically viable theories exist. 相似文献
8.
J. P. Guedes S. Azevedo M. Machado 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):127-135
We have studied, through ab initio calculations, the stability of 60° and 120° boron nitride nanocones containing mono and
multiple boron, nitrogen, and
carbon vacancies. The stability of the vacancies as well as the structures reconstruction mechanism have been investigated.
Our results indicate that the
stability of the cones presenting such vacancies strongly depends on growth conditions. We have also found that multiple vacancies
display formation energies that
are comparable, and in some cases, even lower to the ones presented by monovacancies. Therefore, our results allow us to conclude
that the formation energy does not
depend on the vacancy size. Finally, for 120° cones, we can verify that the stability of the boron and nitrogen vacancies
depends on the position where the atom has
been removed. 相似文献
9.
The optical properties of GeO x film and GeO x /SiO2 multilayer heterostructures (with thickness of GeO x layers down to 1 nm) were studied with the use of Raman scattering and infrared spectroscopy, ellipsometry and photoluminescence spectroscopy including temperature dependence of photoluminescence. The observed photoluminescence is related to defect (dangling bonds) in GeO x and interface defects for the case of GeO x /SiO2 multilayer heterostructures. From analysis of temperature dependence of photoluminescence intensity, it was found that rate of nonradiative transitions in GeO x film has Berthelot type, but anomalous deviations from Berthelot type temperature dependence were observed in temperature dependences of photoluminescence intensities for GeO x /SiO2 multilayer heterostructures. 相似文献
10.
11.
LSDA + U + SO calculations of the electronic structure of helicoidal Fe1 - xCo x Si ferromagnets within the virtual crystal approximation have been supplemented with the consideration of the Dzyaloshinski-Moriya interaction and ferromagnetic fluctuations of the spin density of collective d electrons with the Hubbard interactions at Fe and Co atoms randomly distributed over sites. The magnetic-state equation in the developed model describes helicoidal ferromagnetism and its disappearance accompanied by the occurrence of a maximum of uniform magnetic susceptibility at temperature T C and chiral fluctuations of the local magnetization at T > T C . The reasons why the magnetic contribution to the specific heat at the magnetic phase transition changes monotonically and the volume coefficient of thermal expansion (VCTE) at low temperatures is negative and has a wide minimum near T C have been investigated. It is shown that the VCTE changes sign when passing to the paramagnetic state (at temperature T S ). 相似文献
12.
S. D. Milovidova O. V. Rogazinskaya A. S. Sidorkin T. N. Poyarkova S. A. Bavykin E. V. Ionova 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(9):1295-1298
Dielectric and pyroelectric properties of a composite based on nanodisperse silica hydrosol and ferroelectric triglycinesulfate
(TGS) were investigated. The performed studies allow us to assume that a ferroelectric state exists in this composite. 相似文献
13.
The difference of vector and axial-vector charged current correlators is analyzed by means of QCD sum rules. The contribution of 10-dimensional 4-quark condensates is calculated and its value is estimated within the framework of the factorization hypothesis. It is compared to the result obtained from an operator fit of Borel sum rules in the complex q
2-plane, calculated from experimental data on hadronic
-decays. This fit gives accurate values of the light quark condensate and the quark-gluon mixed condensate. The size of the high-order operators and the convergence of the operator series are discussed.Received: 10 May 2004, Revised: 7 September 2004, Published online: 18 November 2004 相似文献
14.
I. D. Lobov M. M. Kirillova L. N. Romashev M. A. Milyaev V. V. Ustinov 《Physics of the Solid State》2009,51(12):2480-2485
The magnetorefractive effect in Fe(t x , Å)/Cr(10 Å) samples grown by molecular-beam epitaxy with a variable thickness of the iron layer (superlattices, cluster-layered nanostructures) has been studied in the IR region (λ = 2–13 µm) in s and p polarizations of light. The magnetoresistive effect in a dc magnetic field, H ≤ 32 kOe, has been measured on the same samples. The iron layer thickness required for the magnetorefractive response to appear has been found to be t Fe ≥ 3 Å. The correlation between the magnitude of the magnetorefractive effect in the mid-IR region and magnetoresistance has been discussed. 相似文献
15.
16.
I. R. Shein 《Physics of the Solid State》2018,60(10):2012-2018
The energies of formation of vacancies in the carbon and silicon sublattices, the independent elastic constants, the all-round compression, shear and Young’s moduli, and the anisotropy coefficients are determined for the complete and nonstoichiometric cubic phases of 3C-SixCy (x, y = 1.0–0.75) by ab initio methods of the band theory. In the formalism of the density functional perturbation theory (DFPT), the phonon dispersion dependences are obtained for these phases (the comparison with the experiment is given for the complete phase). It is shown that the mechanical characteristics of the phases become strongly anisotropic upon the transition from 3C-SiC0.875 to 3C-SiC0.75. It is established from the analysis of the phonon dispersion curves that the 3C-SiC0.875 and 3C-SiC0.75 phases, in contrast to the complete 3C-SiC phase, are dynamically unstable at T = 0 K. 相似文献
17.
B. M. Ayupov S. A. Prokhorova M. L. Kosinova Yu. M. Rumyantsev 《Optics and Spectroscopy》2012,112(2):201-205
The optical characteristics of nickel films deposited on Si(100) substrates by vacuum thermal evaporation have been studied.
The thickness and optical constants of the films are determined using monochromatic zero ellipsometry, while the inverse problems
are solved within the three-layer optical model of the samples. It is shown that thermal annealing leads to a change in the
optical constants of nickel films in the heating-temperature range of 500–900°C. Boron carbonitride layers deposited on silicon
substrates with a nickel sublayer are analyzed within multilayer optical models, which make it possible to determine the refractive
index and absorption coefficient distributions along the thickness of the synthesized Si(100)/Ni/BC
x
N
y
structure. 相似文献
18.
The magnetic and elastic properties of the Bi1-xCaxMnO3 manganites are studied. The phase transformations revealed are ferromagnet-spin glass (x≥0.15) and spin glass-charge-ordered antiferromagnet (x≥0.25). The ferromagnetic state is characterized by ordering of the Mn3+d x 2-y orbitals. It is suggested that thespin glass state originates from local static Jahn-Teller distortions. The antiferromagnetic charge-ordered and the spin-glass disordered phases coexist in samples with 0.25<x<0.32, which may be due to the charge order-disorder phase transformation being martensitic in character. The magnetic phase diagram is constructed. 相似文献
19.
This paper reports on the results of theoretical investigations carried out for the hydrides Mg2FeH6 and Mg2CoH5 and the mixed hydride Mg2(FeH6)0.5(CoH5)0.5 in terms of the full-potential linearized augmented plane wave (FLAPW) method. It has been shown that the partial substitution of the Co atoms for the Fe atoms leads to a slight increase in the stability of the hydride, but, at the same time, makes it impossible to increase the stability of the alloy. The high stability of the hydrides under investigation has been explained by the strong bonding between atoms of the transition metal and hydrogen. 相似文献
20.
E. C. Niculescu A. Radu 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,80(1):73-82
Tunneling effect on the intersubband optical absorption in a
GaAs/Al
x
Ga1-
x
As quantum well under simultaneous presence of
intense non-resonant laser and static electric fields is theoretically
investigated. Based on the shooting method the quasi-stationary energy
levels and their corresponding linewidths are obtained. By considering the
joint action of the two external fields the linear absorption coefficient is
calculated by means of Fermi’s golden rule and taking into account the
intersubband relaxation. We found that: (i) the linewidth broadening due to
the electron tunneling has an appreciable effect on the absorption spectrum;
(ii) a constant relaxation time adopted in the previous studies could not be
justified even for moderate electric fields, especially in the laser dressed
wells. Our model predicts that the number of absorption peaks can be
controlled by the external applied fields. While in the high-electric fields
the excited states become unbounded due to a significant tunneling of the
electrons, for high laser intensities and low/moderate electric
fields the absorption spectrum has a richer structure due to the
laser-generated resonant states. The possibility of tuning the
resonant absorption energies by using the combined effects of the static
electric field and the THz coherent radiation field can be useful in
designing new optoelectronic devices. 相似文献