共查询到20条相似文献,搜索用时 203 毫秒
1.
Yu. P. Rakovich A. L. Gurskii A. S. Smal’ A. A. Gladyshchuk Kh. Khamadi G. P. Yablonskii M. Khoiken 《Physics of the Solid State》1998,40(5):812-813
The exciton reflectance and photoluminescence spectra of epitaxial ZnSe/GaAs layers with a thickness of 2–4 μm are investigated
in the temperature range 10–120 K. It is shown that one of the causes of the formation of the doublet structure of the A
n=1 photoluminescence band is interference of the exciton radiation at the boundaries of the near-surface dead layer.
Fiz. Tverd. Tela (St. Petersburg) 40, 881–883 (May 1998) 相似文献
2.
The pump-probe experimental method is used to investigate the effect of photoexcited carriers on the dynamics of the exciton
absorption spectra of GaAs / AlxGa1–x
As-multilayer quantum wells. Use of the method of moment analysis for processing the results makes it possible to identify
the simultaneous contribution of changes in oscillator strength and width of the exciton lines in the saturation of exciton
absorption. It was found that the oscillator strength recovers its initial value in the course of the first 100–130 ps, whereas
broadening and energy-shift of the exciton lines is observed for 700–800 ps. These are the first experimental measurements
of the excitation densities at which the oscillator strength of the excitonic state saturates when the latter is perturbed
only by free-electron-hole pairs, and when it is perturbed only by other excitons.
Fiz. Tverd. Tela (St. Petersburg) 40, 1130–1133 (June 1998) 相似文献
3.
I. O. Bashkin M. V. Nefedova V. G. Tissen E. G. Ponyatovskii 《Physics of the Solid State》1998,40(12):1950-1952
The pressure dependence of the superconducting transition temperature in TiD0.74 has been measured up to 30 GPa in a diamond high-pressure chamber. It is found that the deuteride TiD0.74 becomes a superconductor at pressures corresponding to the transition to the high-pressure ζ phase, with a transition temperature that increases from 4.17 to 4.43 K in the interval P=14–30 GPa. The value extrapolated to atmospheric pressure T
c
(0)=4.0 K is significantly lower than the superconducting transition temperature (T
c
=5.0 K) measured earlier in the metastable state obtained by quenching TiD0.74 under pressure. It is assumed that the significant difference of the extrapolated value from the superconducting transition
temperature in the metastable state after quenching under pressure is caused by a phase transition on the path from the stability
region of the ζ phase under pressure to the region of the metastable state at atmospheric pressure.
Fiz. Tverd. Tela (St. Petersburg) 40, 2153–2155 (December 1998) 相似文献
4.
A study has been carried out of the temperature dependences of luminescence spectra on a large number of CdTe/ZnTe structures
differing in average thickness, 〈L
z〉=0.25–4 monolayers (ML), and CdTe layer geometry (continuous, island type). The influence of geometric features in the structure
of ultrathin layers on linewidth, the extent of lateral localization of excitons, their binding energy, and exciton-phonon
coupling is discussed. It is shown that in island structures there is practically no lateral exciton migration. The exciton-phonon
coupling constant in a submonolayer structure has been determined, Γph=53 meV, and it is shown that in structures with larger average thicknesses Γph is considerably smaller. Substantial lateral exciton migration was observed to occur in a quantum well with 〈L
z〉=4 ML, and interaction with acoustic phonons was found to play a noticeable part in transport processes. It has been established
that the depth of the exciton level in a quantum well and structural features of an ultrathin layer significantly affect the
temperature dependences of integrated photoluminescence intensity.
Fiz. Tverd. Tela (St. Petersburg) 41, 717–724 (April 1999) 相似文献
5.
We have investigated the absorption spectrum of thin films of the superionic conductor RbCu4Cl3I2 synthesized on NaCl crystalline substrates. It is shown that the electron and exciton excitations in the energy interval
3–6 eV are associated with optical transitions in the CuHal sublattice, and the edge of the fundamental band is controlled
by optical transitions in the Cu(II)Hal sublattice. It is found that the large band gap of this compound (E
g
=3.86 eV) in comparison with those of CuCl and CuI is a result of the small number of Cu ions in the second coordination sphere.
The temperature dependence of the spectral position and half-width of the low-temperature exciton band reveals features associated
with the phase transitions γ→β (T
c1=170 K) and β→α (T
c2=220 K) and with disordering of the cation sublattice attendant to the transition to the superionic state.
Fiz. Tverd. Tela (St. Petersburg) 40, 1022–1026 (June 1998) 相似文献
6.
A. V. Kudinov Yu. G. Kusraev B. P. Zakharchenya V. N. Yakimovich 《Physics of the Solid State》1998,40(5):823-825
Polarized photoluminescence of Cd1−x
MnxTe crystals in a weak magnetic field has been studied in Faraday and Voigt geometries. A simple method is proposed to determine
the exciton mobility edge and excitonic magnetic-polaron energy. “Forbidden” polarization components of the recombination
radiation have been experimentally detected. It has been established that the moments of magnetic polarons are oriented predominantly
along the {111} axes.
Fiz. Tverd. Tela (St. Petersburg) 40, 894–896 (May 1998) 相似文献
7.
It is established that the necessary conditions for spontaneous relaxation of elastic strain energy in a copper-As60Se40 self-organizing dissipative heterostructure is that the elastic deformation energy and the temperature must reach their threshold
values. It is shown that in the temperature range 270–340 K the spontaneous relaxation of elastic deformation energy is accompanied
by structural-chemical ordering and anomalous diffusion of copper into the glassy chalcogenide semiconductor layer. The maximum
concentration of copper dissolved in the films is 40 at. %. Conductivity inversion from p to n type is observed in doped layers obtained by this method.
Zh. Tekh. Fiz. 69, 128–129 (August 1999) 相似文献
8.
Yu. P. Gnatenko O. A. Shigil’chev E. Rutkovskii G. Contreras-Puente M. Cardenas-Garcia 《Physics of the Solid State》1998,40(4):564-568
Low-temperature photoluminescence, exciton reflection, and multiphonon resonant Raman scattering spectra of Ni-and Co-doped
Zn1−x
MnxTe crystals were investigated. Intense emission occurs in a broad spectral region (1100–17 000 cm−1) in the crystals containing Ni atoms. It is caused by intracenter transitions involving Mn2+ ions and transitions between the conduction band and a level of the doubly charged acceptor. The features of the exciton
photoluminescence and multiphonon resonant Raman scattering involving longitudinal-optical (LO) phonons at various temperatures
are investigated. The insignificant efficiency of the localization of excitons on potential fluctuations in the Zn1−x
MnxTe:Co crystals is established. A temperature-induced increase in the intensity of the 5LO multiphonon resonant Raman scattering
line due to the approach of the conditions for resonance between this line and the ground exciton state is observed in these
crystals.
Fiz. Tverd. Tela (St. Petersburg) 40, 616–621 (April 1998) 相似文献
9.
A transformation of the dimensionality of excitonic states from 2D to 3D with increasing external electric field is observed
in single GaAs/AlxGa1−x
As quantum-well structures with asymmetric barriers. The binding energy of a 2D exciton remains constant over a wide range
of variation of the field, since the decrease in the binding energy is compensated by increasingly larger penetration of the
electronic wave function into the barrier layer, where the exciton binding energy is higher because the effective mass is
larger and the dielectric constant of AlGaAs is lower than that of GaAs. When the maximum of the electron wave function is
displaced into the barrier as the field increases, the exciton binding energy decreases. As the field increases further, a
2D exciton transforms into a quasi-3D exciton, with a heavy hole in the quantum well and an electron in a resonant above-barrier
state.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 3, 207–211 (10 February 1998) 相似文献
10.
Exciton absorption spectra in high-quality β-ZnP2 single crystals have been investigated at T=1.7 K for various directions of the wave vector and various polarization states of the radiation. It has been unambiguously
established that the additional high-energy A series, which in some works has been called a D series and ascribed to ZnP2 crystals, of so-called “rhombic” symmetry,1,8,10,11 is an intrinsic exciton of the β-ZnP2 series. A mixed mode has been detected for the first time, and the energy of the longitudinal exciton has been determined.
The selection rules for the exciton transitions have been analyzed by a group-theoretical approach, and the symmetry of the
nS states of the single exciton has been established on the basis of the experimental data — Γ
2
−
(z).
Fiz. Tverd. Tela (St. Petersburg) 41, 193–202 (February 1999) 相似文献
11.
S. O. Romanovskii A. V. Sel’kin I. G. Stamov N. A. Feoktistov 《Physics of the Solid State》1998,40(5):814-815
A study is made of the effect of electric fields on the exciton states of β-ZnP2 crystals (T=77 K) in structures with Schottky barriers formed by depositing semitransparent electrically-conducting InSnO2 films on the crystal surface. The observed changes in the exciton optical reflection spectra when an electrical potential
is applied to a barrier are explained by the shift and broadening of the exciton level caused by the Stark effect. The experimental
data are compared with calculations based on a theory of exciton optical reflection from planar spatially nonuniform structures.
Fiz. Tverd. Tela (St. Petersburg) 40, 884–886 (May 1998) 相似文献
12.
The evolution of indirect exciton luminescence in AlAs/GaAs coupled quantum wells after excitation by pulsed laser radiation
has been studied in strong magnetic fields (B⩽12 T) at low temperatures (T⩾1.3 K), both in the normal regime and under conditions of anomalously fast exciton transport, which is an indication of the
onset of exciton superfluidity. The energy relaxation rate of indirect excitons measured in the range of relaxation times
between several and several hundreds of nanoseconds is found to be controlled by the properties of the exciton transport,
specifically, this parameter increases with the coefficient of excitonic diffusion. This behavior is qualitatively explained
in terms of migration of excitons between local minima of the random potential in the plane of the quantum well.
Zh. éksp. Teor. Fiz. 114, 1115–1120 (September 1998) 相似文献
13.
Differential absorption spectra of RbAg4I5 have been measured in the exciton absorption region of AgI within the temperature range 27–250 °C. In the same temperature
range, the temperature behavior of the heat capacity of RbAg4I5, Rb2AgI3, and KAg4I5 have been obtained by differential scanning calorimetry. An analysis of the results suggests that, in AgI microcrystals less
than r
cr in size, the upper boundary for stability of the low-temperature β modification is higher by several tens of degrees.
Fiz. Tverd. Tela (St. Petersburg) 40, 852–854 (May 1998) 相似文献
14.
We show that the spectral position of the maxima in the exciton generation rate G in a photovoltaic cell, taking into account the spectral energy distribution in the AM1.5G solar spectrum, is determined
by the absorption bands of its donor and acceptor materials. It varies slightly as the thicknesses of the layers in the cell
change. Interference of light affects only the magnitude of these maxima. For a cell based on a CuPc (copper phthalocyanine)–C60 (fullerene) heterojunction, the G maxima are located at 640 nm, 720 nm (absorption in CuPc) and close to 495 nm (absorption in C60). The photovoltaic cell can be optimized using the ratio of the magnitudes of these maxima and their variations as layer
thicknesses are varied and the exciton diffusion length is taken into account. 相似文献
15.
V. A. Morozova V. S. Vavilov O. G. Koshelev M. V. Chukichev S. F. Marenkin 《Physics of the Solid State》1998,40(5):808-809
A structure corresponding to the n=1, 2, and 3 free-exciton states is observed in the optical transmission spectra of zinc diarsenide at 5 K. The band gap for
E⊥C at temperatures of 5–300 K and the exciton binding energy (17.5 eV) are determined.
Fiz. Tverd. Tela (St. Petersburg) 40, 877–878 (May 1998) 相似文献
16.
A. E. Pochtennyi A. V. Misevich D. I. Sagaidak G. G. Fedoruk 《Physics of the Solid State》1998,40(4):712-714
The conduction mechanism in copper phthalocyanine (CuPc)-polymer composite thin films and their sensitivity to nitrogen dioxide are investigated. It is established that a hopping
conduction mechanism in the regime of single electron hops prevails in these materials at 290–350 K, and the magnitude and
rate of the adsorption-resistance sensitivity to NO2 is higher than in pure CuPc.
Fiz. Tverd. Tela (St. Petersburg) 40, 773–775 (April 1998) 相似文献
17.
R. A. Bisengaliev É. D. Batyrev B. V. Novikov A. V. Sel’kin 《Physics of the Solid State》1998,40(5):806-807
The exciton photoreflection spectra of CdS crystals are studied. It is found that the form of the exciton photoreflection
spectrum is determined by a Stark shift of the exciton energy in the electric field of surface states. The dependences of
the exciton photoreflection spectrum on temperature on the intensity and wavelength of the modulating radiation, and on the
processes by which the photoreflection signal relaxes is determined. An energy scheme is proposed for the surface states which
explains the observed effects of photoinduced changes in the surface field. A correlation is established between the exciton
photoreflection spectrum and the form of the fine structure in the photoconductivity.
Fiz. Tverd. Tela (St. Petersburg) 40, 875–876 (May 1998) 相似文献
18.
I. A. Kudryavtseva E. A. Vasil’chenko A. Ch. Lushchik Ch. B. Lushchik 《Physics of the Solid State》1999,41(3):388-395
The spectrum of luminescent F centers generated in high-purity KCl crystals by 7–10.2-eV photons has been measured at 230 K. The pulsed annealing of these
centers (250–550 K), as well as the dependence of the efficiency of stable F-center generation on irradiation temperature (80–500 K) has been studied. The efficiencies of F
− and Cl
3
−
-center generation are maximum under direct optical creation of self-trapped excitons in the region of the Urbach intrinsicabsorption
tail. Besides the exciton decay with formation of F centers and mobile H centers, a high-temperature exciton decay channel which involves creation of cation defects stabilizing the H centers has been revealed.
Fiz. Tverd. Tela (St. Petersburg) 41, 433–441 (March 1999) 相似文献
19.
A vibronic charge-transfer exciton, which is a pair of Jahn-Teller electron and hole polarons, is considered as a possible
cause of the appearance of the Müller phase in the virtual ferroelectric SrTiO3 and the “green” luminescence in the virtual ferroelectric KTaO3. The two “green” luminescence bands can be associated with emission from two states of a typical intrinsic defect, viz.,
a vibronic charge-transfer exciton trapped by an oxygen vacancy and an isolated vibronic charge-transfer exciton. In both
cases the “green” luminescence corresponds to the recombination of the electron and the hole in the vibronic charge-transfer
exciton, which is accompanied by the emission of light. The properties of the Müller phase can be attributed to mixing of
the normal state and states of the vibronic charge-transfer exciton phase when they interact with polarization in the soft
SrTiO3 matrix under the conditions of a pseudo-Jahn-Teller (pseudo-JT) effect on a soft TO mode of the displacement type. In this
case the vibronic charge-transfer exciton phase forming the low-lying excited states has “order-disorder” degrees of freedom
and exists at temperatures significantly below the point of the order-disorder ferroelectric transition in SrTiO3 at T=T
Q≈37 K. The corresponding lowering of the symmetry of the vibronic charge-transfer exciton phase to polar symmetry leads to
the possibility of a long-period incommensurate phase in such excited states, which arises as a result of the appearance of
a Lifshitz invariant. The valence-band state making the largest contribution of the pseudo-JT effect corresponds to a wave
vector equal to the critical wave vector of the incommensurate vibronic charge-transfer exciton phase. When the temperature
is lowered, the pseudo-JT distortion increases down to ∼T
Q and subsequently saturates in accordance with the saturation of the dielectric constant. The basic assumption in the model
is that the temperature T=T
Q corresponds to the narrow temperature range for the transition from an intermediate to a strong pseudo-JT effect under the
conditions for the realization of polarization tunneling states. The appearance of a significant admixture of states of the
modulated ferroelectric vibronic charge-transfer exciton phase to the ground state under the conditions for the realization
of polarization tunneling states at low temperatures provides an explanation for the principal properties of the Müller phase.
Fiz. Tverd. Tela (St. Petersburg) 40, 907–909 (May 1998) 相似文献
20.
V. V. Shpeizman V. I. Nikolaev B. I. Smirnov A. B. Lebedev V. V. Vetrov S. A. Pul’nev V. I. Kopylov 《Physics of the Solid State》1998,40(9):1489-1491
The influence of ZrO2 particles on the low-temperature deformation of nanocrystalline copper produced by strong plastic deformation is investigated
using equichannel angular pressing. A comparison is made between the deformation characteristics in tension and compression
in the temperature range 4.2–400 K, measured for copper and the composite Cu:0.3 vol. % ZrO2. It is shown that within 4.2–200 K the yield point σ
sm of the composite is higher than that for copper, attaining 680 MPa at 4.2 K, then the yield points are close in value up
to room temperature, and diverge again as the temperature is raised. Possible causes of the dissimilar influence of an impurity
on the strength and plasticity characteristics of nanocrystalline copper in various temperature intervals are discussed.
Fiz. Tverd. Tela (St. Petersburg) 40, 1639–1641 (September 1998) 相似文献