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1.
A. P. Zhernov 《Physics of the Solid State》1999,41(7):1079-1083
This paper discusses the question of how isotopic disorder affects the position of the thermal-conductivity maximum of germanium.
The discussion is in terms of a Callaway-type model. Experimental data on the thermal conductivity of a natural Ge crystal
and of highly enriched Ge70 crystals are analyzed.
Fiz. Tverd. Tela (St. Petersburg) 41, 1185–1189 (July 1999) 相似文献
2.
S. A. Shevchenko 《Journal of Experimental and Theoretical Physics》1999,88(1):66-71
Samples of n-type germanium with a donor concentration N
d=2.4×1016 cm−3 are plastically deformed to a degree of strain equal to 18–40% to detect static conduction by electrons trapped on dislocations
in a system of dislocation grids. In samples with 20%<δ<31%, which retain an electronic type of conductivity, the conductivity for T<8 K, which is weakly temperature-dependent, is associated with conduction by electrons trapped on dislocations. The nonmonotonic
dependence of the conductivity at 4.2 K on the degree of strain as the latter increases from 18% to 40% attests to the existence
of an energy gap between the donor and acceptor dislocation states in strongly plastically deformed germanium.
Zh. éksp. Teor. Fiz. 115, 115–125 (January 1999) 相似文献
3.
Experimental data on the thermal conductivity K(T) of crystals of natural and highly enriched germanium (99.99%) 70Ge with lapped and polished surfaces are analyzed in the temperature range ∼1.5–8 K. In all the samples in the temperature
range ∼1.5–4 K the standard boundary mechanism of scattering dominates. As the temperature is raised, an isotopic scattering
mechanism is observed in the natural samples. In the highly enriched samples the theoretical values of K(T) turn out to be much smaller than the experimental ones. It is conjectured that a Poiseuille viscous flow regime of the phonon
gas emerges in this case.
Zh. éksp. Teor. Fiz. 114, 1757–1764 (November 1998) 相似文献
4.
The effect of normal scattering processes is considered to redistribute the phonon momentum in (a) the same phonon branch
— KK-S model and (b) between different phonon branches — KK-H model. Simplified thermal conductivity relations are used to
estimate the thermal conductivity of germanium, silicon and diamond with natural isotopes and highly enriched isotopes. It
is observed that the consideration of the normal scattering processes involving different phonon branches gives better results
for the temperature dependence of the thermal conductivity of germanium, silicon and diamond with natural and highly enriched
isotopes. Also, the estimation of the lattice thermal conductivity of germanium and silicon for these models with the consideration
of quadratic form of frequency dependences of phonon wave vector leads to the conclusion that the splitting of longitudinal
and transverse phonon modes, as suggested by Holland, is not an essential requirement to explain the entire temperature dependence
of lattice thermal conductivity whereas KK-H model gives a better estimation of the thermal conductivity without the splitting
of the acoustic phonon modes due to the dispersive nature of the phonon dispersion curves.
相似文献
5.
The first-order Raman scattering in isotopically enriched samples of germanium 70Ge, 72Ge, and 74Ge and germanium with the natural isotopic composition is investigated at high pressures. It is found that the isotopic dependence
of the frequency of the LTO(Γ) mode in isotopically pure germanium samples can be described in the harmonic approximation (ν∝m
−1/2). At the same time, the frequency of the LTO(Γ) mode of germanium of natural isotopic composition apparently contains a contribution due to isotopic disorder effects.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 3, 211–214 (10 February 1999) 相似文献
6.
O. V. Malyshkina I. A. Kaplunov M. Yu. Ghavalyan 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(8):1013-1015
The pyroelectric method is used to demonstrate the dependence of the thermal conductivity and thermal diffusivity coefficients of n-type germanium monocrystals on the concentration of antimony impurities (6 × 1013, 1.3 × 1014, 1.7 × 1014, 3.7 × 1014, 6 × 1014 cm?3). The investigated samples are cut from germanium crystals grown from a melt using the Czochralski method with crystallographic orientation [111]. 相似文献
7.
We present computational data on the thermal conductivity of nonlinear waves in disordered chains. Disorder induces Anderson
localization for linear waves and results in a vanishing conductivity. Cubic nonlinearity restores normal conductivity, but
with a strongly temperature-dependent conductivity κ(T). We find indications for an asymptotic low-temperature κ ∼ T
4 and intermediate temperature κ ∼ T
2 laws. These findings are in accord with theoretical studies of wave packet spreading, where a regime of strong chaos is found
to be intermediate, followed by an asymptotic regime of weak chaos (Laptyeva et al, Europhys. Lett.
91, 30001 (2010)). 相似文献
8.
S. V. Rozov V. B. Brudanin A. V. Lubashevskiy S. S. Semikh D. V. Filosofov E. A. Yakushev on behalf of EDELWEISS Collaboration 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(4):464-466
The results from measurements of thermal neutron flux in the EDELWEISS II experiment aimed at the direct detection of WIMPs
(weakly interacting massive particles) by means of cryogenic germanium bolometers are described. Detailed knowledge of the
neutron background is of crucial importance for the experiment, since neutrons with the MeV energy range of scattering seem
to be hard to distinguish from the expected WIMP signal within the bolometers. Monitoring of the thermal neutron flux is performed
using a mobile detection system with a low background proportional 3He counter. The neutron flux measurements were performed both outside and inside the device’s shielding, in the direct proximity
of a cryostat with built-in germanium detectors. The sensitivity of the created thermal neutron detection system is on the
level of 10−9 neutron (cm2 s)−1. 相似文献
9.
V. M. Matyushin 《Technical Physics》1999,44(7):804-806
An investigation is made of the diffusion of gold in germanium under the influence of the energy released by the recombination
of hydrogen atoms to form molecules. Crystals of n-type germanium with gold films (d=1×10−7 m) are exposed to atomic hydrogen for various times (up to 104 s) at temperatures close to room temperature. The diffusion of gold in the germanium is analyzed by laser mass spectrometry,
and also by measuring the surface resistance, the minority carrier lifetime, and the infrared transmission spectra. Mechanisms
are proposed for the stimulation of heterodiffusion and accompanying processes.
Zh. Tekh. Fiz. 69, 73–76 (July 1999) 相似文献
10.
The thermal conductivity of diamond-paraffin wax composites prepared by infiltration of a hydrocarbon binder with the thermal
conductivity λ
m
= 0.2 W m−1 K−1 into a dense bed of diamond particles (λ
f
∼ 1500 W m−1 K−1) with sizes of 400 and 180 μm has been investigated. The calculations using universally accepted models considering isolated
inclusions in a matrix have demonstrated that the best agreement with the measured values of the thermal conductivity of the
composite λ = 10–12 W m−1 K−1 is achieved with the use of the differential effective medium model, the Maxwell mean field scheme gives a very underestimated
calculated value of λ, and the effective medium theory leads to a very overestimated value. An agreement between the calculation
and the experiment can be provided by constructing thermal conductivity functions. The calculation of the thermal conductivity
at the percolation threshold has shown that the experimental thermal conductivity of the composites is higher than this critical
value. It has been established that, for the composites with closely packed diamond particles (the volume fraction is ∼0.63
for a monodisperse binder), the use of the isolated particle model (Hasselman-Johnson and differential effective medium models)
for calculating the thermal conductivity is not quite correct, because the model does not take into account the percolation
component of the thermal conductivity. In particular, this holds true for the calculation of the heat conductance of diamond-matrix
interfaces in diamond-metal composites with a high thermal conductivity. 相似文献
11.
A. A. Selezenev A. Yu. Aleinikov P. V. Ermakov N. S. Ganchuk S. N. Ganchuk R. E. Jones 《Physics of the Solid State》2012,54(3):462-467
The thermal conductivity coefficient of the germanium crystal lattice has been calculated by molecular dynamics simulation.
Calculations have been performed for both the perfect crystal lattice and the crystal lattice with defects such as monovacancies.
For the perfect germanium single crystal, the dependence of the thermal conductivity coefficient on the lattice temperature
has been obtained in the temperature range of 150–1000 K. The thermal conductivity coefficient of the germanium lattice has
been calculated as a function of the monovacancy concentration. 相似文献
12.
Abstract The subsurface layers with quasi-metal hole conductivity have been observed in n- and p-Ge immersed into liquid He under the 60Co-gamma-irradiation. three conditions are to be fulfilled simultaneously for the production of the layers: low temperature, direct contact between helium and germanium and gammairradiation. 相似文献
13.
A. P. Zhernov 《Physics of the Solid State》1998,40(10):1658-1660
The linear thermal expansion coefficient of crystal lattices of germanium with different isotopic compositions is analyzed.
Fiz. Tverd. Tela (St. Petersburg) 40, 1829–1831 (October 1998) 相似文献
14.
A. N. Vystavkin D. V. Shuvaev L. S. Kuz’min M. A. Tarasov E. Aderstedt M. Willander T. Claeson 《Journal of Experimental and Theoretical Physics》1999,88(3):598-602
This paper describes the design and experimental testing of a high-sensitivity hot-electron bolometer based a film of normal
metal, exploiting the Andreev reflection from superconductor boundaries, and cooled with the help of a superconductor-insulator-normal
metal junction. At the measured thermal conductivity, G≈6×10−12 W/K, and a time constant of τ=0.2 μs, and a temperature of 300 mK, the estimated noise-equivalent power NEP=5×10−18 W/Hz1/2, assuming that temperature fluctuations are the major source of noise. At a temperature of 100 mK, the thermal conductivity
drops to G≈7×10−14 W/K, which yields NEP=2×10−19 W/Hz1/2 at a time constant of τ=5 μs. The microbolometer has been designed to serve as a detector of millimeter and FIR waves in space-based radio telescopes.
Zh. éksp. Teor. Fiz. 115, 1085–1092 (March 1999) 相似文献
15.
B. Zeini A. Freimuth B. Büchner M. Galffy R. Gross A.P. Kampf M. Kläser G. Müller-Vogt L. Winkler 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,20(2):189-208
Measurements of the thermal conductivity (kxx) and the thermal Hall effect (kxy) in high magnetic fields in Y- and Bi-based high-T
c
superconductors are presented. We describe the experimental technique and test measurements on a simple metal (niobium).
In the high-T
c
superconductors kxx and kxy increase below T
c
and show a maximum in their temperature dependence. kxx has contributions from phonons and quasiparticle (QP) excitations, whereas kxy is purely electronic. The strong increase of kxy below T
c
gives direct evidence for a strong enhancement of the QP contribution to the heat current and thus for a strong increase
of the QP mean free path. Using kxy and the magnetic field dependence of kxx we separate the electronic thermal conductivity ( k
xx
el
) of the CuO
2
-planes from the phononic thermal conductivity ( k
xx
ph
). In YBa2Cu3O
7 - δ
k
xx
el
shows a pronounced maximum in the superconducting state. This maximum is much weaker in Bi2Sr2CaCu2O
8 + δ
, due to stronger impurity scattering. The maximum of k
xx
el
is strongly suppressed by a magnetic field, which we attribute to the scattering of QPs on vortices. An additional magnetic
field independent contribution to the maximum of kxx occurs in YBa2Cu3O
7 - δ
, reminiscent of the contribution of the CuO-chains, as determined from the anisotropy in untwined single crystals. Our data analysis reveals that below T
c
as in the normal state a transport (τ) and a Hall (
) relaxation time must be distinguished: The inelastic (i.e. temperature dependent) contribution to τ is strongly enhanced in the superconducting state, whereas
displays the same temperature dependence as above T
c
. We determine also the electronic thermal conductivity in the normal state from kxy and the electrical Hall angle. It shows an unusual linear increase with temperature.
Received 23 August 2000 相似文献
16.
Filler-matrix thermal boundary resistance of diamond-copper composite with high thermal conductivity 总被引:1,自引:0,他引:1
A composite material with a high thermal conductivity is obtained by capillary infiltration of copper into a bed of diamond
particles of 400 μm size, the particles having been pre-coated with tungsten. The measured thermal conductivity of the composite
decreases from 910 to 480 W m−1 K−1 when the coating thickness is increased from 110 to 470 nm. Calculations of the filler/matrix thermal boundary resistance
R and the thermal conductivity of the coating layer λ
i
using differential effective medium, Lichtenecker’s and Hashin’s models give similar numerical values of R and λ
i
≈ 1.5 W m−1 K−1. The minimal thickness of the coating h ∼ 100 nm necessary for ensuring production of a composite while maximizing its thermal conductivity, is of the same order
as the free path of the heat carriers in diamond (phonons) and in copper (electrons). The heat conductance of the diamond/tungsten
carbide coating/copper interface when h is of this thickness is estimated as (0.8–1) × 108 W m−2 K−1 and is at the upper level of values characteristic for perfect dielectric/metal boundaries. 相似文献
17.
A. P. Zhernov 《Journal of Experimental and Theoretical Physics》1998,87(2):357-364
Features of the thermal expansion coefficient α(T) of crystal lattices with different isotopic compositions have been analyzed. The case of germanium lattices has been studied
in detail.
Zh. éksp. Teor. Fiz. 114, 654–668 (August 1998) 相似文献
18.
V. A. Konstantinov V. P. Revyakin V. V. Sagan O. I. Pursky V. M. Sysoev 《Journal of Experimental and Theoretical Physics》2011,112(2):220-225
Thermal conductivity Λ
P
of solid cyclohexane is measured at a pressure P = 0.1 MPa in the temperature range from 80 K to the melting point, which covers the ranges of low-temperature orientationally
ordered phase II and high-temperature orientationally disordered phase I. Thermal conductivity Λ
V
is measured at a constant volume in orientationally disordered phase I. The thermal conductivity measured at atmospheric
pressure decreases with increasing temperature as Λ
P
∝ T
−1.15 in phase II, whereas Λ
P
∝ T
−0.3 in phase I. As temperature increases, isochoric thermal conductivity Λ
V
in phase I increases gradually. The experimental data are described in terms of a modified Debye model of thermal conductivity
with allowance for heat transfer by both phonons and “diffuse” modes. 相似文献
19.
V. I. Ozhogin N. A. Babushkina L. M. Belova A. P. Zhernov E. E. Haller K. M. Itoh 《Journal of Experimental and Theoretical Physics》1999,88(1):135-137
The first experimental and theoretical investigation of the difference in the temperature behavior of the linear expansion
coefficients of single crystals grown from isotopically highly enriched and natural germanium is reported. A comparison of
the data for 70Ge and natGe crystals reveals the significant influence of isotopic composition over a wide range of temperatures 30–230 K.
Zh. éksp. Teor. Fiz. 115, 243–248 (January 1999) 相似文献
20.
The effect of electric fields on the electrical conductivity of PbTe films with block sizes smaller than the Debye screening
length is studied. As the temperature is varied, a readjustment of the potential well is observed due to thermal spread of
barriers with height ϕkT and the expansion of higher barriers. Spatial ensembles, which consist of several blocks that increase rapidly with temperature,
are established for each T. This process leads to an increase in the height of the potential barriers as the linear size of these ensembles increases.
This determines the potential well in these films and their nonlinear properties, which originate in the nonlinear percolation
conductivity of a microscopic crystalline system with intergranular barriers. A comparison with the experimental data of Shklovskii
shows that the scale length of the spatial inhomogeneity a=3.7×10−6 cm at T=4.2 K corresponds to the average block size. The value of a increases with temperature, reaching 5×10−4 cm at T=240 K. This mechanism for electrical conductivity is compared with the hopping conductivity with a variable hopping length.
The negative differential resistance in the structures examined here is found to be electrothermal in nature.
Zh. éksp. Teor. Fiz. 116, 276–298 (July 1999) 相似文献