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51.
The iron silicides samples were prepared by annealing of iron films evaporated onto silicon wafers and capped with amorphous silicon thin overlayers. Semiconducting FeSi2 phase is formed by annealing at the temperatures from 550°C to 850°C. The optical properties of the FeSi2 layers have been deduced from reflectance and transmittance measurements carried out in the temperature range of (77–380) K. The spectral dependence of the absorption coefficient favours direct allowed transitions with forbidden energy gap of 0.87eV at the room temperature. The application of a simple three-parameter semiempirical formula to the temperature dependence of the direct energy gaps leads to the following best fit parameters: the band gap at zero temperature E
g (0) = (0.895 ± 0.004)eV, the dimensionless coupling parameter S = 2.0 ± 0.3, and the average phonon energy <hw> = (46 ± 8)meV. By examining all the reported triplets of parameters for -FeSi2 fabricated by different techniques and thermal processes, an obvious discrepancy can be found for the lattice coupling parameter and average phonon energy, although the bandgaps at 0 K are very similar. Unlike the theoretical prediction and the earlier reported result, our results do not show any evidence of a particularly strong electron-phonon interaction, which would give the lower carrier mobilities. -FeSi2 seems to be an intriguing material where states with energies near the band edges permit ambiguous interpretation of the character of transitions. From optical model for the thin film-substrate system we found the index of refraction to be (5–5.9) in the photon energy interval from 0.65 to 1.15eV. There is also indication of an additional higher-energy absorption edge at l.05eV. 相似文献
52.
R. Yahiaoui H. Němec P. Kužel F. Kadlec C. Kadlec P. Mounaix 《Applied Physics A: Materials Science & Processing》2011,103(3):689-692
This work presents theoretical and experimental investigations of a tunable metamaterial which exhibits negative permeability
in the THz frequency range. The tunability is obtained by temperature changes, and the sample consists of an array of high-permittivity
SrTiO3 (STO) rods micromachined by a femtosecond laser. Structures exhibiting a negative permeability on multiple frequency bands
are also investigated and a proper choice of the dimensions of the pattern allows us to achieve a substantial broadening of
the frequency band with negative μ. 相似文献
53.
Elzain M. Al Rawas A. Yousif A. Gismelseed A. Rais A. Al-Omari I. Bouziane K. Widatallah H. 《Hyperfine Interactions》2004,158(1-4):205-209
Time differential perturbed γ-γ angular correlation technique was used to measure the magnetic hyperfine field (MHF) at Tb
sites in the intermetallic compound Tb3In5 using the 140La → 140Ce nuclear probe. The measurements were carried out in the temperature range of 8 to 295 K. Two different temperature dependent
magnetic frequencies were observed below 30 K, which were assigned as 140Ce substituting the two inequivalent Tb sites in the orthorhombic structure of Tb3In5. The temperature dependence of MHF also shows a possible deviation from an expected Brillouin-like behavior for temperatures
below 18 K. A Néel transition at 27 K was observed from magnetization measurements in the samples. The magnetization as a
function of the applied magnetic field was measured at two temperatures, 5 and 40 K, and the results show antiferromagnetic
and a typical paramagnetic behavior, respectively. In both cases it was not observed saturation under high magnetic field. 相似文献
54.
G. M. Abramova A. M. Vorotynov G. A. Petrakovskii N. I. Kiselev D. A. Velikanov A. F. Bovina R. F. Al’mukhametov R. A. Yakshibaev É. V. Gabitov 《Physics of the Solid State》2004,46(12):2225-2228
Electrical, resonant, and magnetic properties of intercalated copper chromium disulfide CuCrS2 are studied. It is established that CuCrS2 is an antiferromagnetic semiconductor with Néel temperature TN=40.7 K and an effective magnetic moment of 4.3µB. Anomalies in the electrical, magnetic, and resonant properties of CuCrS2 are found at Tc=110 K, which suggest an electron transition accompanied by alteration of the valences of the 3d-metal ions. 相似文献
55.
X‐ray absorption near‐edge structure (XANES) spectroscopy was used to examine the oxidation state of Zn, Fe and Cu in 22 normal and 23 tumour regions spread over 30 formalin‐fixed, paraffin‐embedded tissue samples of human primary invasive breast cancer. A micro‐mapping analysis of the metal distribution in the tissue was performed prior to the XANES analysis to identify and localise the metals in the tumour and normal tissue regions. The aim of this study was to identify the oxidation state of Zn, Fe and Cu in normal and tumour tissues of the breast, in order to correlate the oxidation state of these elements with the carcinogenesis process. The position of the Zn K‐edge in normal and tumour tissues suggests that Zn exists in a bounded form. The shape of the Cu K‐edge XANES spectra and the first derivative spectra of normal and tumour tissues shows that a significant portion of the total copper is present as Cu (I). Nevertheless, the position of the edges in the normal and tumour tissue spectra does not exclude the presence of Cu (II). The shape and position of both normal and tumour regions of the tissue suggest that they contain mixtures of Fe (II) and Fe (III) ions with a significant fraction being Fe (III). However, normal tissue regions were found to have a higher fraction of Fe (II) compared to the tumour tissues. In order to estimate the best target for therapy, more information is required about the relative abundance of Zn, Fe and Cu binding proteins, their oxidation state and their localisation at the subcellular level. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
56.
V. I. Al’shits V. N. Lyubimov A. Radowicz 《Journal of Experimental and Theoretical Physics》2005,101(1):107-119
The conditions of existence of the zero components of electric field E and electric induction D accompanying a volume acoustic wave propagating in a piezoelectric medium have been studied. General equations describing the positions of the zero-field lines E(m) = 0 and the zero-induction points m0, such that D(m0) = 0 on the unit sphere (m2 = 1) of the wave propagation directions, are obtained. General theorems determining the conditions ensuring the existence of such lines and points, even in triclinic crystals, are formulated. The relationship between such directions and various elements of the crystal symmetry is analyzed. The vector fields D(m), which are always orthogonal to the wave normals m, in the vicinity of the zero-induction points m0 exhibit certain orientational singularities characterized by the Poincaré indices n = 0, ±1, ±2. The general analytical expressions are obtained for the n values in crystals with arbitrary anisotropy and specified for a number of crystals belonging to various symmetry classes. The conditions of stability of the orientational singularities with respect to small perturbations of the material moduli and a change in the crystal symmetry are considered. 相似文献
57.
M. Ježabek J. Karczmarczuk M. Rożańska 《Zeitschrift fur Physik C Particles and Fields》1985,29(1):55-60
In the framework of the dual parton model we calculate the spectra of secondary antibaryons in \(\bar p\) -nucleus non-annihilation inelastic interactions. We find that the number of antibaryons in the backward hemisphere in the \(\bar p\) -nucleon centre-of-mass frame can grow with the atomic number of the nucleus. 相似文献
58.
Temperature dependence of electronic and ionic components of electric conductivity and dielectric permittivity of amorphic compounds Ag0.25Sb0.25S0.5, (AgSbS2)0.95· (SbSI)0.05 and (AgSbS2)0.9·(SbSI)0.1 in the temperature range of 290–380 K have been investigated. The experimental data show that glasses investigated are solid electrolytes. Ionic conductivity as well as dielectric permittivity of the glasses Ag-Sb-S may be changed by introduction of SbSI. 相似文献
59.
, - 17,6 , . , (8±4)·10–23, (7±4)·10–23 (4±2)·10–23
2. , - . 相似文献
60.