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1.
TlGaSe2 and TlGaS2 single crystals were grown by the modified Bridgman-Stockbarger method. We report the result of an experimental study of the optical absorption of TlGaSe2 and TlGaS2 crystals. The absorption measurements were performed in steps of 10 K. The direct and indirect band gaps for TlGaSe2 and TlGaS2 samples were calculated as a function of temperature. The phonon energies in TlGaSe2 and TlGaS2 crystals were calculated as (39±4) and (9±4) meV at 240 K, respectively. At 10 K, direct and indirect band gaps were found as 2.294 and 2.148 eV for TlGaSe2, 2.547 and 2.521 eV for TlGaS2 crystals, respectively. The abrupt changes were observed in the direct and indirect band gaps in the some temperature ranges. These changes were interpreted as phase transformation temperatures. The steepness parameters and Urbach energy for TlGaSe2 and TlGaS2 samples increased with increasing sample temperature in the range (10–320) K. 相似文献
2.
R. M. Sardarly O. A. Samedov A. I. Nadzhafov I. Sh. Sadykhov 《Physics of the Solid State》2003,45(6):1137-1140
The temperature dependences of the permittivity of TlInS2 crystals doped with 0.1 at. % Cr, Mn, Yb, Sm, Bi, or La are investigated, and the dependence of the phase transition temperature on the ion radius of the dopant impurity is determined. It is revealed that manganese and chromium substitute for indium in the TlInS2 crystal lattice, whereas ytterbium, samarium, bismuth, and lanthanum ions occupy octahedral holes in an In4S10 tetrahedral complex and, thus, produce an internal pressure responsible for the shift in the temperature of phase transitions toward the high-temperature range. 相似文献
3.
The results of the study of photoluminescence and its excitation spectra in TlGaSe2 single crystals are presented. The ability of these layered crystals to be cleaved by plates with mirror faces, being a consequence
of sharp asymmetry of the chemical bond, makes them promising materials for photoelectric converters. 相似文献
4.
A. N. Georgobiania V. P. Tokarev A. M. Evloeva E. V. Perlov 《Bulletin of the Lebedev Physics Institute》2009,36(11):317-320
The results of the study of the Raman spectrum of TlGaSe2 single crystals are presented. The ability of these layered crystals to cleave into plates with mirror faces, being a consequence
of significant asymmetry of the chemical bond, makes them promising materials for photoelectric converters. 相似文献
5.
A. P. Odrinskii M.-H. Yu. Seyidov T. G. Mammadov V. B. Alieva 《Physics of the Solid State》2017,59(3):457-462
The results of the phenomenological study of the abnormal photoresponse kinetics in layered TlGaSe2 ferroelectric semiconductor have been discussed over the temperature range T of ~170–280 K corresponding to the paraelectric phase of crystal. Taking into account the alterations in the photoresponse kinetics temperature, the main mechanisms of anomalies caused by the spatial inhomogeneity of localized and nonlocalized charges in the bulk of the crystal have been assumed. The mechanism of parametric resonance is suggested to be favored by the photogalvanic currents in the crystal. 相似文献
6.
S. N. Mustafaeva 《Physics of the Solid State》2004,46(6):1008-1010
Frequency dependence of the dissipation factor tanδ, the permittivity ɛ, and the ac conductivity σac across the layers in the frequency range f=5×104−3×107 Hz was studied in layered TlGaS2 single crystals. A significant dispersion in tanδ was observed in the frequency range 106−3×107 Hz. In the range of frequencies studied, the permittivity of TlGaS2 samples varied from 26 to 30. In the frequency range 5×104−106 Hz, the ac conductivity obeyed the f
0.8 law, whereas for f>106 Hz σac was proportional to f
2. It was established that the mechanism of the ac charge transport across the layers in TlGaS2 single crystals in the frequency range 5×104−106 Hz is hopping over localized states near the Fermi level. Estimations yielded the following values of the parameters: the
density of states at the Fermi level N
F=2.1×1018 eV−1 cm−3, the average time of charge carrier hopping between localized states τ=2 μs, and the average hopping distance R=103 ?.
__________
Translated from Fizika Tverdogo Tela, Vol. 46, No. 6, 2004, pp. 979–981.
Original Russian Text Copyright ? 2004 by Mustafaeva. 相似文献
7.
A. N. Vtyurin S. V. Goryainov N. G. Zamkova V. I. Zinenko A. S. Krylov S. N. Krylova A. D. Shefer 《Physics of the Solid State》2004,46(7):1301-1310
Raman scattering spectra of RbMnCl3 are measured at room temperature under high hydrostatic pressure. The results are interpreted based on first principles lattice dynamics calculations. The experimental data obtained correlate with the calculations in the low frequency domain but disagree slightly in the region of high-frequency vibrations. The transition from the hexagonal to the cubic perovskite phase observed earlier (near 0.7 GPa) was confirmed, and new transitions to lower symmetry distorted phases were discovered (at 1.1 and 5 GPa). 相似文献
8.
The electronic structure of cerium systems, the hybridization of 4 f and outer-shell electrons, and the influence of the position of the localized 4 f level with respect to the Fermi level E
F in the conduction band have been investigated. The CeCu6, CePd3, CeSi2, and CeF3 systems have been studied using X-ray photoelectron spectroscopy. The densities of states have been calculated by the tight-binding
linearized muffin-tin orbital method within the atomic sphere approximation, which takes into account the covalent character
of bonds and the nonspherical distribution of the electron density. The results obtained from the calculations of the total
density of states are in good agreement with the valence band X-ray photoelectron data for the systems under investigation.
It has been shown that the differences in the properties of the cerium systems are determined by the specific features of
their electronic structure. A strong interatomic interaction is characteristic of heavy-fermion systems. 相似文献
9.
R. M. Sardarly O. A. Samedov I. Sh. Sadykhov V. A. Aliev 《Physics of the Solid State》2003,45(6):1118-1121
The relaxor properties of Fe-doped TlInS2 crystals are investigated. It is shown that Fe-doped TlInS2 compounds exhibit all features inherent in relaxor ferroelectric materials. The temperature range of existence of the microdomain (relaxor) state and the temperature of the transition from this state to a macro-domain state are determined. 相似文献
10.
M. -H. Yu. Seyidov R. A. Suleymanov S. S. Babaev T. G. Mamedov G. M. Sharifov 《Physics of the Solid State》2008,50(1):108-117
The effect of external fields (dc electric field, light illumination) on the memory effect of the incommensurate phase in the ferroelectric-semiconductor TlGaSe2 is studied using the measured dielectric constant. The results obtained are discussed. It is shown for the first time that the effect of external fields on the anomaly related to the memory effect in TlGaSe2 can be reduced to the following universal empirical rule: when a sample is held for many hours at a constant temperature T 0 in the temperature range of the incommensurate phase in a dc electric field, the deflection amplitude in the low-temperature part of the anomaly in the temperature dependence of the relative change in the dielectric constant Δ?/? increases (the deflection in the high-temperature part of the Δ?/? anomaly disappears) as compared to this segment in the dependence obtained during isothermal annealing of this sample at the same temperature without an electric field. The crystal remembers its thermal history at a temperature that is several kelvins higher than T 0. Light illumination increases the deflection amplitude in the high-temperature part of the Δ?/?(T) anomaly and shifts the temperature at which the crystal remembers its thermal history toward lower temperatures with respect to T 0. 相似文献
11.
The effect of gamma radiation on the permittivity ? and the electrical conductivity σ of TlGaS2 crystals is investigated at frequencies of 0.1, 1, and 10 kHz and 1 MHz in the temperature range 200–370 K. It is shown that an increase in the temperature leads to an increase in the permittivity ? and the electrical conductivity σ. The electrical conductivity σ of TlGaS2 samples irradiated with a dose of 10 MR and then measured at all frequencies and the permittivity ? of samples irradiated with a dose of 1 MR and then measured at frequencies of 10 kHz and 1 MHz increase, whereas further accumulation of the dose results in a decrease in the values of ? and σ. The parameters studied are characterized by a considerable dispersion: as the frequency increases, the permittivity ? decreases and the electrical conductivity σ increases. 相似文献
12.
A. S. Yurkov 《Physics of the Solid State》2007,49(8):1536-1542
The effect of the improper ferroelastic transition on the IR spectra of the Hg2Cl2 crystal is considered. It is shown that, due to lattice anharmonicity, the distortions caused by the phase transition give rise to mixing of the normal modes of the higher symmetry phase of the crystal, which results in the appearance of extra poles in the frequency dependence of the lattice permittivity. Experimentally, such extra poles manifest themselves in the appearance of extra lines in the IR absorption spectra. Symmetry analysis shows that this effect in Hg2Cl2 is strongly anisotropic in the plane normal to the tetragonal axis of the crystal. 相似文献
13.
V. B. Kapustyanyk R. M. Pasternak A. Z. Kalush M. R. Panasyuk V. S. Tsibul’skii V. P. Rudyk R. Ya. Serkiz 《Journal of Applied Spectroscopy》2007,74(2):283-288
We have analyzed the surface morphology of single crystal samples of lead diiodide and studied the absorption edge and the
temperature variation of their photoluminescence spectra. We have established that the zirconium impurity is uniformly incorporated
into the crystal lattice of the samples and promotes appreciable quenching of photoluminescence due to formation of electron
traps.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 252–257, March–April, 2007. 相似文献
14.
R. M. Shymkiv S. A. Sveleba I. V. Karpa I. N. Katerynchuk I. M. Kunyo E. I. Phitsych 《Journal of Applied Spectroscopy》2012,78(6):823-828
Optical absorption spectra in thin [N(CH3)4]2CuCl4 crystals in the thickness range 10 μm ≤ d < 100 μm have been studied. Strengthening of the crystal field has been found with
a decrease in the [N(CH3)4]2CuCl4 crystal size. The reasons for absorption band shifts in the visible region depending on the [N(CH3)4]2CuCl4 crystal thickness and the manifestation of a size effect in crystals with an incommensurate superstructure are discussed. 相似文献
15.
The effect of pressure on the structural and electronic properties of lithium, sodium, potassium, and ammonium perchlorates have been studied in terms of the density functional theory with allowance for the Van der Waals dispersion interaction. The pressure dependences of the geometric parameters, the band gaps, the densities of states, the charge distributions, and the atomic charges are calculated. The compressibilities of the perchlorates are found to be anisotropic, which is due to the differences of the lattice parameters and the nature of interatomic bonds. Ammonium cation is rotated under pressure around axis b at an angle of ~9°. The band gaps of the perchlorates are ~4.5–4.7 eV and increase with pressure. 相似文献
16.
A. V. Malakhovskii S. L. Gnatchenko I. S. Kachur V. G. Piryatinskaya A. L. Sukhachev V. L. Temerov 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(5):721-723
Optical absorption spectra of the trigonal crystal of TbFe3(BO3)4 in the vicinity of the 7F6 → 5D4 transition in a Tb3+ ion were studied as a function of temperature (2–70 K) and magnetic field strength (0–60 kOe) at 2 K. The splitting of the
excited states of Tb3+ due to both the magnetic ordering of iron and an external magnetic field was determined. Abrupt splitting of the absorption
lines of Tb3+ at temperature TN of the magnetic ordering of the subsystem of iron was revealed, suggesting that the nature of such splitting is not entirely
magnetic. 相似文献
17.
18.
Pseudopotential calculations of the electronic structure of the compounds are performed to an approximation of the density functional theory within the basis of localized orbitals. The band structure and total and projected state density are calculated, and a complete interpretation of the x-ray spectra is given.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 68–72, January 2005. 相似文献
19.
V. V. Brazhkin Y. Katayama A. G. Lyapin S. V. Popova Y. Inamura H. Saitoh W. Utsumi 《JETP Letters》2005,82(11):713-718
The results of investigating the phase diagrams of ZnCl2 and AlCl3 halides, as well as the structure of the shortrange order of the corresponding melts under pressures up to 6.5 GPa, by the method of energy-dispersive x-ray diffraction are reported. When a ZnCl2 crystal is compressed, a phase transition occurs from the γ phase (HgI2 structure type) to the δ phase (distorted CdI2 structure, WTe2 type). The structural studies of the liquid state of ZnCl2 and AlCl3 indicate that the intermediate-range order decreases rapidly in the tetrahedral network of both melts as the pressure increases to 1.8 and 2.3 GPa for ZnCl2 and AlCl3, respectively. With further compression, the transitions in both melts occur with a change in the structure of the short-range order and with an increase in the coordination number. In this case, the transition in AlCl3 occurs at ≈4 GPa and is a sharp first order transition, whereas the transition in ZnCl2 occurs more smoothly in a pressure range of 2–4 GPa with a maximum intensity near 3 GPa. Thus, the AlCl3 and ZnCl2 compounds exemplify the existence of two phenomena—gradual decay of intermediate-range structural correlations and a sharper liquid-liquid coordination transition. 相似文献
20.
The melting temperatures of H2, D2; N2 and CH4 are analysed. The computed results are in very good agreement with the experimental data in each solid. Further, the analysis
indicates the presence of the melting maximum in these solids. 相似文献