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1.
Temperature and frequency dependence of dielectric permittivity and tangent of the dielectric loss angle are studied in epitaxial gallium arsenide structures. It is shown that nonmonotonic change in with temperature is caused by change in the volume of conductive gallium microinclusions and a difference between the structural perfection of the layer and substrate. The space charge relaxation time on inhomogeneities is evaluated (10–5–10–6 sec) and its contribution to GaAs dielectric properties is evaluated. An oscillation in dielectric permittivity upon heating is observed and explained.Deceased.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 18–21, February, 1989. 相似文献
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N. T. Pokladok I. I. Grygorchak B. A. Lukiyanets D. I. Popovich 《Physics of the Solid State》2007,49(4):715-718
Intercalated crystals of indium and gallium selenide are prepared. It is shown that laser intercalation of nickel into GaSe samples leads to a giant magnetoresistive effect whose magnitude and sign depend on the concentration of the guest component. The giant magnetoresistive effect in the InSe intercalation compounds is considerably weaker and does not exceed 5%. The experimental data obtained are explained in terms of magnetic delocalization (localization) of charge carriers with the participation of states of intercalated magnetically active atoms in the vicinity of the Fermi level. 相似文献
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Y. I. Golovin S. D. Victorov A. I. Tyurin A. N. Kochanov A. V. Schyklinov T. S. Pirozhkova I. A. Shuvarin 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(5):518-521
Size effects of hardness are studied and numeric values of Young’s modulus E, hardness H, and fracture toughness coefficient Kc of individual phases and interphase boundaries of polycrystalline samples of ferruginous quartzite are determined by means of micro- and nanoindentation methods. It is found that the interphase boundary of magnetite and hematite is the one most strengthened, while the boundary of the hematite and quartz is the one least durable. 相似文献
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Structure and electronic properties of GaN nanotubes (GaNNTs) are investigated by using ab initio density functional theory. By full optimization, the optimized structures (bond-lengths and angles between them) of zigzag GaNNTs (n,0) and armchair GaNNTs (n,n) (4<n<11) are calculated. The difference between nitrogen ring diameter and gallium ring diameter (buckling distance) and semiconducting energy gap in term of diameter for zigzag and armchair GaNNTs have also been calculated. We found that buckling distance decreases by increasing nanotube diameter. Furthermore, we have investigated the effects of nitrogen and gallium vacancies on structure and electronic properties of zigzag GaNNT (5,0) using spin dependent density functional theory. By calculating the formation energy, we found that N vacancy in GaNNT (5,0) is more favorable than Ga vacancy. The nitrogen vacancy in zigzag GaNNT induces a 1.0μB magnetization and makes a polarized structure. We have shown that in polarized GaNNT a flat band near the Fermi energy splits to occupied spin up and unoccupied spin down levels. 相似文献
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《Superlattices and Microstructures》1995,17(4):393-396
We have studied the electronic properties of single twin boundaries and twinning superlattices in lead sulfide. The results are compared against those obtained previously for such structures based on diamond/zincblende type materials, and substantial differences are noted. It is found that lead sulfide twinning superlattices can have significantly wider or narrower band gaps than the homogeneous material, depending on whether the twin interface is occupied by anion or cation atoms. 相似文献
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Using first-principles calculations, the structure, stability, and electronic properties of BN sheets with grain boundaries
(GBs) are investigated. Two types of GBs, i.e., zigzag- and armchair-oriented GBs, are considered. Simulation results reveal
that the zigzag-oriented GBs are more stable than the armchair-oriented ones. The GBs induce defect levels located within
the band gap, which must be taken into account when building nanoelectronic devices. 相似文献
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N. L. Dmitruk 《Russian Physics Journal》1980,23(1):24-35
Conclusion This review has analyzed studies of the surface physics of monocrystalline gallium arsenide as of 1978. Special attention has been given to peculiarities in structure, lattice dynamics, and the spectra of surface electron states in atomically pure and real GaAs surfaces as compared to Ge and Si. These peculiarities manifest themselves in the specifics of the electrophysical properties of GaAs surfaces, quasisurface conductivity, capacitance of structures with a potential barrier, nonequilibrium transfer processes, radiant processes, and other phenomena characteristic of polar noncentrally symmetric semiconductors. At present the development of gallium arsenide surface physics is proceeding in two directions: 1) study of the micromechanism of electronic processes on atomically pure surfaces; 2) study of the nature and characteristics of various electron-ion processes on a real surface. Important information on the surface can be obtained by study of phenomena in which surface quasiparticles participate — phonons, plasmons, excitons, and mixed polaritons.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 38–51, January, 1980. 相似文献
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A novel PVA/CuI nanocomposite polymer electrolyte layer synthesized via the reduction of CuCl2 by NaI in an aqueous PVA solution. The as-prepared films were characterized by X-ray diffraction, scanning electron microscope, as well as impedance spectroscopy. The obtained results indicated the formation of hexagonal CuI nano particles of ≈55 nm sizes embedded in the PVA matrix. In addition, the study of dielectric parameters and conductivity of PVA/CuI nanocomposite in wide range of temperature and frequency are given and discussed. The frequency dependence of ac-conductivity suggests power law with an exponent 0.026 < s < 0.73 which predicts hopping of charge carriers. The bulk conductivity showed activation with temperature, significant values of activation energy are deduced and discussed. An average value of the energy gap width, 2.05 eV obtained using optical absorption in UV–visible spectra for PVA/CuI nanocomposite polymer electrolyte. 相似文献
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E. V. Balashova B. B. Krichevtsov F. B. Svinarev V. V. Lemanov 《Physics of the Solid State》2013,55(5):995-1001
Polycrystalline textured films of deuterated glycine phosphite consisting of single-crystal blocks with lateral dimensions ~(50–100) μm and a thickness d ~ (1–5) μm have been grown by evaporation on NdGaO3(100) and α-Al2O3 substrates with preliminarily deposited interdigitated electrodes, as well as on Al substrates. The c* (Z) crystallographic axis in the blocks is normal to the film plane, and the a (X) axis and the polar axis b (Y) are oriented in the film plane. The temperature dependences of the capacitance of the structures measured with the interdigitated electrode system reveal a strong dielectric anomaly at the film transition to the ferroelectric state. The phase transition temperature T c depends on the degree of deuteration D of the glycine phosphite. The maximum value T c = 275 K obtained in the structures studied corresponds to a degree of deuteration of the glycine phosphite D ~ 50%. The frequency behavior of the dielectric hysteresis loops in glycine phosphite films differs radically from that of the previously studied films of deuterated betaine phosphite, which evidences that polarization switching in these structures proceeds by different mechanisms. It has been that application of a dc bias to the electrodes changes the shape of the dielectric hysteresis loops and shifts them along the electric field axis. The shift of the loops depends on the sign, magnitude, and time of application of the bias. Possible mechanisms underlying the induced unipolarity are discussed. 相似文献
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Radheshyam Rai 《Solid State Communications》2004,129(5):305-309
Polycrystalline samples of Pb0.9(La1−zBiz)0.1(Zr0.55Ti0.45)0.975O3 [referred as PLBZT] (z=0.0, 0.3, 0.5 and 0.7) have been synthesized by a high-temperature solid-state reaction technique. X-ray diffraction analysis suggests the formation of single-phase compounds with monoclinic structure. The dielectric studies of the compounds as a function of temperature (room temperature, RT to 350 °C) at frequency (1, 10 and 100 kHz) show that the compounds undergo a phase transition of diffuse type. Diffusivity (γ) study of phase transition of these compounds provided its value between 1 and 2, indicating the variation of degree of disordering in the system. Measurement of dc resistivity (ρ) as a function of temperature (RT to 350 °C) at a constant biasing field suggests the compounds have negative temperature coefficient of resistance. 相似文献
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L. Kozielski M. Adamczyk A. Lisinska-Czekaj T. Orkisz M. Piechowiak D. Czekaj 《Phase Transitions》2013,86(6-7):427-433
In the present work the (Pb0.84Ba0.16)(Zr0.54Ti0.46)O3 (PBZT) solid solution has been synthesized. The process of preparation was investigated by simultaneous thermal analysis (STA) and X-ray diffraction method. The hot pressing method was utilized for densification of ceramic samples. Dielectric properties of donor- and acceptor-doped PZT-type ceramics were measured within the temperature range including the phase transition region. Frequency-dependent relaxation behaviour in PBZT ceramics was found. The structural phase transition at T?=?(517?±?3)?K was determined by X-ray diffraction method. Arrhenius plot of total conductivity derived from ac impedance spectroscopy measurements was used for characterisation of phase transition. Changes in activation energy were found characteristic of phase transition in PBZT ceramics. 相似文献
14.
A study of opto-electronic properties of gallium chalcogenides (GaS, GaSe and GaTe) is presented here. An investigation into the various effective charge parameters ( and their correlation with ionicity have been done. The energy dependence of optical effective charge parameter (neff) have been discussed with respect to the band structure of respective chalcogenides. The low frequency optical dielectric constants (?00) have been derived using reflectivity data and the obtained values of ?00 have been found in agreement with the values obtained using Moss relation as also with the reported experimental data. The difference in the arrangement of fundamental structures of GaS and GaSe on one hand and GaTe on the other hand does not seem to effectively change the opto-eleetronic properties and the fundamental structure (which is common in all the three chalcogenides) is mainly responsible for determining these properties. The effect of surface conditions on the values of neff and ?∞ have been evaluated for GaTe. Using derived values of neff and ?∞ the value of Penn gap have been determined. The Penn gap thus obtained is shown to be in agreement with the reflectivity data. In the passing we also show that essentially the Varshni formula explains fairly well the temperature dependence of the energy gap for gallium chalcogenides and the constants involved are evaluated. 相似文献
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The problem of calculating the long-time-limit effective diffusivity in stable two-phase polycrystalline material is addressed for the first time. We make use of a phenomenological model where the high-diffusivity interphase boundaries are treated as connected ‘coatings’ of the individual grains. The derivation of expressions for the effective diffusivity with segregation is along the lines of the analysis by Maxwell in . Monte Carlo computer simulation using lattice-based random walks on a very fine-grained mesh is employed to test the validity of the expressions. It is shown that, for the specific cases analysed, the derived expressions for the effective diffusivity are in very good agreement with results from the simulations. Since the pattern of behaviour is not entirely clear at present, it is difficult to guide the choice for the best expression in a given case. The equivalent of the Hart equation for this problem is also derived. This equation is shown to be invariably in poor agreement with simulation results. 相似文献
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《Solid State Ionics》2006,177(35-36):3175-3178
GaPO4 crystals were grown from solutions of aqueous phosphoric acid. A critical factor influencing the high-temperature behaviour of the material is its content of −OH groups, which was determined by FT-IR spectroscopy. From an Arrhenius plot of the electrical conductivity of platinum electroded crystals, a single activation energy of 1.68 ± 0.07 eV to temperatures of about 950 °C was derived irrespective of the source of the crystals. A conduction model based on proton migration via a hydrogen bridge bond between an OH group and an adjacent oxygen ion is proposed. 相似文献
20.
In this paper, dielectric properties of various thick PVP films cured at temperatures between 125° C and 200 °C are investigated. The thicknesses of PVP films are adjusted by varying their concentration in PGMEA solvent from 10 wt% to 2.5 wt%. Through FT-IR, C–V, SEM, and AFM analyses, the optimum curing process temperatures (150 °C for 10 wt% and 7.5 wt% samples, and 175 °C for 5 wt% samples) where PET substrates can be thermally endured are proposed in terms of their low hysteresis voltage in the C–V curve (1–2 V in 10 wt% samples, below 1 V in 7.5 wt% samples, and 0.5 V in 5 wt% samples). 相似文献