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1.
A bi-epitaxial (001)YBa2Cu3O7−δ
/(110)BaZrO3/(001)CeO2 three-layer heterostructure has been grown on (100)SrTiO3 by laser ablation. The epitaxial relations between the layers making up the heterostructure were derived from x-ray diffraction
data. The I
cRn product for the bi-epitaxial Josephson junctions thus obtained was within 1–1.5 mV for 4.2 K, and 30–60 μV for 77 K. The normal resistance R
n=(2–5 Ω) was practically independent of temperature. The magnetic field dependences of I
c had typically a clearly pronounced main maximum, followed by distorted subsequent peaks. Interaction of the Josephson ac
current with self-induced electromagnetic waves at the 45° grain boundary and with external microwave radiation (f=11 GHz) produced current steps in the I-V characteristics of the bi-epitaxial junctions at the corresponding voltages.
Fiz. Tverd. Tela (St. Petersburg) 39, 1732–1738 (October 1997) 相似文献
2.
O. V. Anisimov V. P. Germogenov L. S. Khludkova O. V. Yurkovskii 《Russian Physics Journal》1999,42(1):38-46
The effect of an invertedp-region along the free surface ofn-Al
x
Ga1−x
Sb on the reverse current ofp−n structures from the given solid solution is analyzed. Expressions which describe “collection” of the inverted layer current
on the cylindrical surface of ann-region are discussed. The contribution of the near-surface and bulk components to the reverse current ofp−n structures with a semi-infiniten-region is estimated. For structures with a two-layern-region of finite thickness we have calculated the dependence of the near-surface current on the voltage across thep−n structure, the thickness of then-region, and its composition and doping level. We have compared the calculated current-voltage characteristics with experiment
using a Al0.15Ga0.85Sbp−n structure as an example.
Tomsk State University, Tomsk. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, Vol. 42, No. 1, pp. 34–40,
January, 1999. 相似文献
3.
An electron paramagnetic resonance (EPR) line shape simulation for nitroxide spin probes in the motional narrowing region
was carried out assuming axially symmetricg andA tensors and with different anisotropies of rotationN (=R
∥/R
⊥) whereR
∥ andR
⊥ are, respectively, elements of the diffusion tensor along and perpendicular to its principal axisz′. In addition, it was assumed that the principal axes of the diffusion tensor coincide with the molecular axes. Each of three
casesz′=x,z′=y andz′=z, which result from cyclic permutations of the molecular axesx, y andz with thez′,y′ andx′ axes of the diffusion tensor, yields its typical EPR spectrum characterized by the relative intensities of the low-, center-
and high-field lines. The parameter δ defined by and calculable from the intensities of the three lines was found to vary
linearly withN for thez′=x andz′=y cases and, as anticipated, to be practically constant at a value of 1 for thez′=z case. This suggested a method for estimatingN for a probe from its EPR spectrum. Experimental spectra over a narrow temperature range (1°C) in the vicinity of the nematic-to-isotropic
transition (about 34.6°C) ofN-(4-n-butylbenzilidene)-4-amino-2,2,6,6-tetramethylpiperidine-1-oxide at a mole fraction of 1·10−3 in 4-n-pentyl-4′-cyanobiphenyl showed a pattern of peak heights characteristic of thez′=x case with δ values that gave, neglecting effects of the mean field, higher and lowerN values in the nematic and isotropic regions, respectively. Analysis of other similar systems in the literature gave similar
results. 相似文献
4.
The association of theH
2
O molecule and the effect of UV radiation on complexes with hydrogen bonds were studied. Complete ab initio calculations of
the S0 and S1 states were performed for the(H
2
O)
n
,n=2–6, complexes. Changes in the effective atomic charges, bond orders, and electron densities on the bonds were analyzed. The
analysis and the calculated cross sections of potential surfaces along theOH bonds reveal that one of theOH complex bonds is in decay. The electron excitation is shown to be localized at a molecule of the(H
2
O)
n
,n=2–6, complex, while for theH
2
O complexes withn>2 the excitation involves, for the most part, a freeOH
f bond of the water molecule that does not participate in the formation of the hydrogen bondO...H. A direct correlation is observed between the behavior of theOH
f bond and the changes in the atomic charges Q(O) and Q(Hf) reflecting the electron density redistribution.
V. D. Kuznetsov Siberian Physical-Technical Institute at Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh
Zavedenii, Fizika, No. 5, pp. 8–12, May, 1999. 相似文献
5.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Kouji Satou 《Applied Physics A: Materials Science & Processing》2009,94(1):57-64
The resultant local Seebeck coefficient α
R (=α
S−α
T) at the interface of a thermoelement has not yet been measured, although it is an important factor governing the thermoelectric
efficiency, where α
S is the local Seebeck coefficient and α
T is the one caused by the Thomson effect. It is shown in this paper that α
S, α
T, and α
R of the p- and n-type Cu/Bi–Te/Cu composites are obtained analytically and experimentally on the assumption that the local temperature of
the composite on which the temperature difference ΔT is imposed varies linearly with changes in position along the composite. They were indeed estimated as a function of position
from the local experimental data of R,ΔI,ΔT, and V generated by applying an additional current of ±I to the composite, where R is the electrical resistance and ΔI is a current generated by the composite. As a result, it was found that the absolute values of α
S at the hot interface of the p- and n-type composites are approximately 1.5 and 1.4 times higher than their lowest values in the middle region of the composite,
respectively, while those of α
T are less than 8% of α
S all over the composite and are so small that the relation α
R≈α
S can be held. We thus succeeded in measuring α
R at the interfaces of the composite. 相似文献
6.
Takashi Yasuda Masayoshi Tonouchi Shuzo Takano 《Czechoslovak Journal of Physics》1996,46(Z3):1265-1266
Current-voltage (I–V) characteristics are studied in the intrinsic Josephson junctions of Bi2Sr2CaCu2Oy single crystals. In order to examine the influence of self-heating, a current pulse (∼0.2 μsec) is applied to the mesas of
40 μmϕx0.15 μm patterned on the crystal. As a consequence, in contrast to small characteristic voltageV
c in the continuous-current measurement, theV
c data is found comparable to the BCS value. Moreover, theI–V curve is nearly ohmic forl>l
c
, implying that the nonlinearity under the continuous current is due to heating. The quasiparticle resistance forT<T
c
is also presented by an estimate from the characteristic voltage. 相似文献
7.
Zhaokui Wang Shigeki Naka Hiroyuki Okada 《Applied Physics A: Materials Science & Processing》2010,100(4):1103-1108
We have investigated the performance of organic light-emitting devices (OLEDs) with a rubrene-doped mixed single layer by
using 4,4′-bis[N-(1-napthyl)-N-phenyl- amion] biphenyl (α-NPD) as hole transport layer. Comparing to a conventional heterostructure OLED, equal luminance vs. current density characteristics
were obtained. In addition, maximum power efficiency was threefold improved, and the achieved value was 5.90 lm/W by optimizing
a mixing ratio of hole and electron transport materials. By evaluating the temperature dependence of the
J
–
V
characteristics for electron-injection dominated device, the electron injection from Al/LiF to mixed organic layer is attributed to Schottky thermal emission model. And the barrier height of the electron injection from Al/LiF into mixed single layer was obtained to be 0.62 eV, which is lower
than Al/Alq3 interface. Meanwhile, the mixed single-layer device exhibited superior operational durability at a half-luminance of 2,250 h
under a constant current operation mode. The reliability was improved with a factor of two compared to the heterostructure
device due to the improvement of stability in mixed organic molecules and removal of the heterojunction interface in the mixed
single-layer device. 相似文献
8.
Summary The emerging overview of the distant tail suggests to interpret some aspects of the magnetic-field observations obtained during
January 1968 by Pioneer 8 in the region of expected tail (∼500R
E) in terms of different magnetic-field regimes which might find correspondence in the experimental observations performed
at ∼240R
E by ISEE-3. At Pioneer position tail-like fields are typically accompanied by significant values of theB
y component while evidence for a wave activity which mostly perturbs the trasversal magnetic-field components is occasionally
detected during tail-like encounters.
Paper presented at the V Cosmic Physics National Conference, S. Miniato, November 27–30, 1990. 相似文献
9.
Liu Wei Chen Shifu Zhang Sujuan Zhao Wei Zhang Huaye Yu Xiaoling 《Journal of nanoparticle research》2010,12(4):1355-1366
In this article, the p-type CuBi2O4 powder was prepared by the solid-state reaction method. The p–n heterojunction photocatalyst p-CuBi2O4/n-TiO2 was prepared by ball milling. The photocatalyst was characterized by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance
spectroscopy, scanning electron microscopy (SEM), and photoluminescence emission spectra. The photocatalytic activity of the
photocatalyst was evaluated by photocatalytic reduction of Cr2O7
2− and photocatalytic oxidation of methyl orange (MO). The results showed that the photocatalytic activity of the p–n heterojunction photocatalyst p-CuBi2O4/n-TiO2 was much higher than that of TiO2 and the mixture of p-CuBi2O4–n-TiO2 without ball milling under visible and UV light irradiation. The optimal percentage of doped p-CuBi2O4 is 20 wt%. Compared with pure TiO2, the photoabsorption wavelength range of the photocatalyst is extended greatly toward visible light and improves the utilization
of the total spectrum. The effect of ball milling time on the photocatalytic activity of the photocatalyst was also investigated.
The optimum ball milling time is 6 h. The mechanisms of influence of p-CuBi2O4 on the photocatalytic activity of p-CuBi2O4/n-TiO2 were also discussed by the p–n junction principle and the valance band theory. 相似文献
10.
In YBa2Cu3O7 − x
films grown on sapphire bicrystal substrates, the Josephson junctions are prepared based on artificial grain boundaries formed
by the turn of the crystal lattices about the [100] axis. The films are deposited by the laser ablation method on the buffer
CeO2 layer. The critical film temperature reaches 88.5 K with a transition width of 1.5 K. Junctions from 2 to 3-μ m wide are
integrated into the planar log-periodic antennas and their characteristics are measured at 77 K. The characteristic voltage
I
c
R
n
reaches 570 μV. With exposure to external radiation at a frequency of 113 GHz, the Shapiro steps were observed on the current-voltage
characteristic. The temperature sensitivity of this detector placed in a quasi-optical receiving unit is measured. At the
modulation of the input radiation temperature 77 K/300 K, a response of more than 200 nV is observed at the detector output.
At the modulation frequency, intrinsic noise is about 1 nV/Hz1/2, which corresponds to a temperature resolution of 1 K.
Original Russian Text ? M. Tarasov, E. Stepantsov, A. Kalabukhov, M. Kupriyanov, D. Winkler, 2007, published in Pis’ma v Zhurnal
éksperimental’noĭ i Teoreticheskoĭ Fiziki, 2007, Vol. 86, No. 11, pp. 828–831. 相似文献
11.
Osamu Yamashita Hirotaka Odahara Takahiro Ochi Jun-ichi Shigeto 《Applied Physics A: Materials Science & Processing》2009,97(1):133-141
The local Seebeck coefficient α
L
and the resultant Seebeck coefficient α
R
of M/Bi0.88Sb0.12/M (M = Cu and Ni) composites with different thicknesses t
Bi–Sb of Bi–Sb alloy were measured as functions of z and T, where T is the absolute temperature, z is the distance from a center of Bi–Sb alloy to the middle point of two probes and α
L
and α
R
were measured using two probes separated by s=1.0 mm and s=t
Bi−Sb+0.1 mm, respectively. As a result, α
L
was enhanced extremely at the position of 0.2–0.3 mm away from the interfaces, while the local temperature along a composite
varies linearly with changes in z within Bi–Sb alloy. The local maximum of α
R
at 344 K appeared at t
Bi−Sb≈0.9 mm, so that it is expected to increase up to −167 μV/K at t
Bi−Sb=0.87 mm from the expression fitted well to the experimental data, which is 2.1 times as large as the intrinsic α at 344 K of Bi–Sb alloy. Such a local enhancement in α
L
would probably be caused by a temperature gradient across the depletion layer formed at the interface. The thermoelectric
figure of merit ZT of a composite with an optimum t
Bi−Sb of 0.87 mm is expected to reach the large value of 0.98 at 344 K, which corresponds to 4.5 times as high a value as ZT=0.22 at 344 K of Bi–Sb alloy. It is thus considered that the increase in α
L
at the interface is available as a useful mean of further increase in ZT of thermoelectric devices. 相似文献
12.
V. A. Kul’bachinskii I. A. Churilov P. D. Mar’yanchuk R. A. Lunin 《Journal of Experimental and Theoretical Physics》1997,85(5):989-993
The galvanomagnetic properties of single crystals of the semimagnetic semiconductors Hg1−x
MnxTe1−y
Sey with 0.01<y<0.1 and x=0.05 and 0.14 in the temperature range 4.2–300 K are investigated. The features of the temperature dependence of the Hall
coefficient R
H and the complicated behavior of R
H in a magnetic field are attributed quantitatively to the existence of three groups of current carriers, viz., electrons and
two types of holes, for which the temperature dependences of the densities and mobilities are obtained. A transition from
p-type to n-type conductivity is observed as the Se content is increased, and the negative magnetoresistance simultaneously gives way
to positive magnetoresistance.
Zh. éksp. Teor. Fiz. 112, 1809–1815 (November 1997) 相似文献
13.
Sarath C. Puthentheradam Dieter K. Schroder Michael N. Kozicki 《Applied Physics A: Materials Science & Processing》2011,102(4):817-826
The feasibility of a storage element with inherent rectifying or isolation properties for use in passive memory arrays has
been demonstrated using a programmable metallization cell structure with a doped (n-type) silicon electrode. The Cu/Cu–SiO2/n-Si cell used in this study switches via the formation of a nanoscale Cu filament in the Cu–SiO2 film which results in the creation of a Cu/n-Si Schottky contact with soft reverse breakdown characteristics. The reverse bias leakage current in the on-state diode is
dependent on the programming current employed as this influences the area of the electrodeposit and hence the area of the
Cu/n-Si junction. The programming current also controls the on-state resistance of the device, allowing multi-level cell (MLC)
operation, in which discrete resistance levels are used to represent multiple logical bits in each physical cell. The Cu/Cu–SiO2/n-Si elements with heavily doped silicon electrodes were readily erasable at voltage less than −5 V which allows them to be
re-programmed. Lightly doped silicon electrode devices were not able to be erased due to their very high reverse breakdown
voltage but exhibited extremely low leakage current levels potentially allowing them to be used in low energy one-time programmable
arrays. 相似文献
14.
The absorption spectra and the melting and crystallization kinetics of CuCl nanocrystals in glass are investigated in the
range of particle radii 1–30 nm. Three discontinuities are found on the curves representing the size dependence of the melting
point T
m(R) and the crystallization point T
c(R). As the particle radius gradually decreases from 30 nm in the range R⩽12.4 nm there is a sudden 60° drop in the temperature T
c in connection with the radius of the critical CuCl nucleus in the melt. A 30° drop in T
m is observed at R=2.1 nm, and a second drop of 16° in the temperature T
c is observed for CuCl particles of radius 1.8 nm. The last two drops are associated with changes in the equilibrium shape
of the nanoparticles. In the range of smaller particles, R⩽1.34 nm the T
c(R) curve is observed to merge with the T
m(R) curve, owing to the disappearance of the work of formation of the crystal surface during crystallization of the melt as
a result of the zero surface tension of CuCl particles of radii commensurate with the thickness of the effective surface layer.
An increase in the size shift of the exciton energy is observed in this same range of CuCl particle radii (1–1.8 nm). The
size dependence of the melting and crystallization temperatures of the nanoparticles is attributed to variation of the free
energy in the surface layer of a particle.
Fiz. Tverd. Tela (St. Petersburg) 41, 310–318 (February 1999) 相似文献
15.
T. Matsuzaki K. Nagamine K. Ishida N. Kawamura S. N. Nakamura M. Kato H. Sugai M. Tanase K. Kudo N. Takeda G. H. Eaton 《Hyperfine Interactions》2001,138(1-4):295-305
We have measured X-rays and neutrons associated with the muon catalyzed t–t fusion process at the RIKEN-RAL Muon facility.
In the X-ray measurement, we observed Kα and Kβ X-rays originating from the muon sticking process in muon catalyzed t–t fusion, and obtained the Kα X-ray yield and the Kβ/Kα intensity ratio. An average recoil energy of the (μ−α) atoms in a solid T2 medium was determined from the observed Doppler broadening width of the Kα X-ray line. The obtained t–t fusion neutron has shown an exponential time spectrum with a single component and a continuous
energy spectrum with a maximum energy of 9 MeV. We have determined the t–t fusion neutron yield, the t–t fusion cycling rate
and the muon sticking probability from the neutron data. The obtained maximum neutron energy is a very peculiar value from
the view point of the reaction Q value (11.33 MeV) with the three-particle decay mode at the exit channel: t + t → α + n + n + Q. The obtained neutron energy distribution was analyzed by a simple model with two neutron energy components; reasonable agreement
has been obtained, suggesting a strong (n–α) correlation in the exit channel of the t–t muon catalyzed fusion reaction.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
16.
A new method for calculation of Clebsch-Gordan coefficients (CGCs) of the Lie algebrau(n) and its quantum analogU
q(u(n)) is developed. The method is based on the projection operator method in combination with the Wigner-Racah calculus for
the subalgebrau(n−1) (U
q(u(n−1))). The key formulas of the method are couplings of the tensor and projection operators and also a tensor form of the projection
operator ofu(n) andU
q(u(n)). It is shown that theU
q(u(n)) CGCs can be presented in terms of theU
q(u)(n−1)) q−9j-symbols.
Presented at the 9th International Colloquium: “Quantum Groups and Integrable Systems”, Prague, 22–24 June 2000.
Supported by Russian Foundation for Fundamental Research, grant 99-01-01163.
Supported in part by the U.S. National Science Foundation under Grant PHY-9970769 and Cooperative Agreement EPS-9720652 that
includes matching from the Louisiana Board of Regents Support Fund. 相似文献
17.
The behavior of the electrode systems M,O2/O2 (M = porous Pd, Pt, A and dense In2O3; O2− = ZrO2-based single-crystal solid electrolyte) was studied by means of impedance measurements. The examination of the Pt,O2/O2− electrode system showed that the constant phase element (CPE) can be attributed to a nonuniform distribution of current at
the electrode surface. It was observed that the CPE parameters n and B in the expression YCPE = B (jω)n may be related by B=(Cdl)n (RΩ)n-1, where Cdl is the double layer capacitance and RΩ the resistance of the electrolyte in the cell. Then, Cdl of the electrode - electrolyte interface could be determined. The specific Cdl of the oxidized noble metals and india electrodes is nearly one order of magnitude lower than Cdl of the electrodes in the metallic state. The Cdl value of all the electrodes studied depends little or is independent of temperature and oxygen pressure. It is concluded
that the Helmholtz model of double layer structure does not contradict the Cdl behavior. 相似文献
18.
F. Bridou M. Cuniot-Ponsard J.-M. Desvignes A. Gottwald U. Kroth M. Richter 《Applied Physics A: Materials Science & Processing》2011,102(3):641-649
Efficient polarizing as well as non-polarizing mirrors for a wavelength of λ=121.6 nm (hydrogen Lyman-α radiation) are necessary to achieve an experimental determination of the magnetic field in the solar corona through the Hanle
effect. We have designed, realized and characterized such mirrors. These consist of glass coated with a thin-film stack. The
coatings use the most reflective (Al) and most transparent (fluorides) materials at this wavelength. Different coatings were
explored which involve an increasing number of films in the coating stack. At the incident angle of maximum polarization where
the p-polarized reflectivity R
p is minimized, an s-polarized reflectivity R
s as high as 69% is experimentally obtained with a coating made of a Fabry–Pérot resonator. To our knowledge, this value is
the highest ever reported for a polarizing mirror at this wavelength. Additionally, efficient non-polarizing mirrors have
been designed and realized by using a two-layer coating (MgF2/Al/glass). By optimizing the fluoride layer thickness, a mirror with non-polarizing properties in the whole range of incident
angles was realized. 相似文献
19.
A quantum dynamical problem has been analytically solved for a two-level system where localized states L
0 and R
0 are strongly coupled with reservoirs of local oscillations {L
n
} and {R
n
}. It is additionally assumed that the spectra of reservoirs are equidistant and the coupling constants are the same. It has
been shown that the evolution of states L
0 and R
0 in recurrence cycles depends on three independent factors, which characterize exchange with the two-level system, exchange
of L
0 with {L
n
} (R
0 with {R
n
}) and the phonon-induced decay of {L
n
} and {R
n
}. In addition to coherent oscillations with the frequency of the two-level system, Δ, and dissipative tunneling with a rate
Δ2/πC
2 (where C is the matrix element of the coupling of L
0 and R
0 with L
n
and R
n
), a new regime appears where L-R transitions are induced by the partial recovery of the populations of L
0 and R
0 in each recurrence cycle due to synchronous transitions from reservoirs. These transitions induce repeating changes in the
populations of the states of the two-level system (Loschmidt echo). The number and width of the echo components increase with
the cycle number. Evolution becomes irregular because of the mixing of the contributions from pulses of the neighboring cycles,
when the cycle number k exceeds the critical value k
c = π2
C
2. Unlike the populations, their cycle-average values remain regular at k ≫ k
c. When Δ ≪ πC
2, the cycle-average populations oscillate with a frequency of ΔΩ/πC
2 irrespective of mixing. The frequency of oscillations of the populations of the states {L
n
} and {R
n
} is approximately nΩ(Δ/2πC
2)2, where Ω is the spacing between the neighboring levels of the reservoir and nΩ is the difference between the energies of the states L
0 and L
n
. The appearance of the mentioned low-frequency oscillations is due to the formation of collective states of the two-level
system that are “dressed” by the reservoir. The predicted oscillations can be detected by femtosecond spectroscopy methods. 相似文献
20.
The renormalization of quantum field theory twists the antipode of a noncocommutative Hopf algebra of rooted trees, decorated
by an infinite set of primitive divergences. The Hopf algebra of undecorated rooted trees, ℋ
R
, generated by a single primitive divergence, solves a universal problem in Hochschild cohomology. It has two nontrivial closed
Hopf subalgebras: the cocommutative subalgebra ℋladder of pure ladder diagrams and the Connes–Moscovici noncocommutative subalgebra ℋCM of noncommutative geometry. These three Hopf algebras admit a bigrading by n, the number of nodes, and an index k that specifies the degree of primitivity. In each case, we use iterations of the relevant coproduct to compute the dimensions
of subspaces with modest values of n and k and infer a simple generating procedure for the remainder. The results for ℋladder are familiar from the theory of partitions, while those for ℋCM involve novel transforms of partitions. Most beautiful is the bigrading of ℋ
R
, the largest of the three. Thanks to Sloane's superseeker, we discovered that it saturates all possible inequalities. We
prove this by using the universal Hochschild-closed one-cocycle B
+, which plugs one set of divergences into another, and by generalizing the concept of natural growth beyond that entailed
by the Connes–Moscovici case. We emphasize the yet greater challenge of handling the infinite set of decorations of realistic
quantum field theory.
Received: 31 January 2000 / Accepted: 7 July 2000 相似文献