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71.
Hongyan Wang Guohua Jia Yan Wang Zhenyu You Jianfu Li Zhaojie Zhu Fugui Yang Yanping Wei Chaoyang Tu 《Optical Materials》2007,29(12):1635-1639
Novel pure and cobalt-doped magnesium borate crystals (Mg3B2O6) have been grown successfully by the Czochralski technique for the first time. Crystal growth, X-ray powder diffraction (XRD) analysis, absorption spectrum, fluorescence spectrum as well as fluorescence decay curve of Co2+:Mg3B2O6 (MBO) were described. From the absorption peaks for the octahedral Co2+ ions, the crystal-field parameter Dq and the Racah parameter B were estimated to be 943.3 cm−1 and 821.6 cm−1, respectively. The fluorescence lifetime of the transition 4T1(4P) → 4T2 centered at 717 nm was measured to be 9.68 ms. 相似文献
72.
73.
L. A. Almeida N. K. Dhar M. Martinka J. H. Dinan 《Journal of Electronic Materials》2000,29(6):754-759
The technique of spectroscopic ellipsometry (SE) has been utilized to monitor in real-time and precisely control the surface
temperature of Hg1−xCdxTe during molecular beam epitaxy. Due to the temperature dependence of the Hg sticking coefficient under Hg-deficient growth
conditions, the near-surface composition of an epilayer is extremely sensitive to surface temperature. SE data were acquired
in real time and modeled using a previously established library of dielectric functions of Hg1−xCdxTe as a function of composition. Utilizing SE-generated compositional profiles as a guide, substrate heating power was adjusted
in such a way as to minimize composition transients. To demonstrate the effectiveness of the technique, we have used SE to
control the temperature of HgCdTe epilayer surfaces during deposition on three-inch (211)CdZnTe/ZnTe/Si composite substrates
mounted on indium free holders. 相似文献
74.
Lithium antimony lead germanate glasses doped with different concentrations of Cr2O3 (ranging from 0 to 0.5 mol %) were synthesized. The optical absorption and ESR spectral studies have indicated that there is a gradual increase in presence of octahedral chromium ions with increase of Cr2O3 concentration in the glass network. These studies have also revealed that a fraction of chromium ions get oxidized into Cr5+ and Cr6+ states. IR and Raman spectroscopic studies have pointed out that there is an increasing degree of depolymerization of the titled glass network with increase of Cr2O3 content. The dielectric parameters (viz., dielectric constant, loss and electrical modulus coefficients measured over a wide range of frequency and temperature) and also ac conductivity were found to increase with increase of Cr2O3 content. The reasons for such increase were discussed quantitatively in terms of various polarization mechanisms coupled with structural variations of the glass network. 相似文献
75.
Sebastian Oliver Klemm Janine-Christina Schauer Bernd Schuhmacher Achim Walter Hassel 《Electrochimica acta》2011,(11):76
The combination of a capillary based microelectrochemical flow cell system and downstream UV–vis analytics allows obtaining synchronized electrochemical and spectroscopic data in a fully automated mode. This method combination can be generally applied to microelectrochemical studies in which an electrochemical species is released or consumed during the electrochemical reaction. For the example of pure zinc surfaces, the characterization of the integrated spectroscopic system is presented with a Zn2+ detection limit below 0.1 μmol l−1 using Zincon as complexing agent. A parameter screening of the effect of pH in the range of 6.6–9.0 in borate buffer reveals a linear increase in zinc dissolution with proton concentration but a distinct step in the open circuit potential from the active state (around −700 mV SHE, pH 6.6–7.1) to the passive state (around −300 mV SHE, pH 7.4–9.0) indicating the formation of a closed passive layer. This mechanism is strongly influenced by sulfate anions which increase the dissolution rate of the passive film and promote the active state as monitored by the dissolution profile and OCP (open circuit potential) values. Within the scope of this parameter variation, the congruency between OCP transients, potentiodynamic sweeps and time resolved dissolution profiles is discussed. 相似文献
76.
E. Barrera-Calva J.C. Martínez-Flores L. Huerta A. Avila M. Ortega-Lpez 《Solar Energy Materials & Solar Cells》2006,90(15):2523-2531
Due to their unique optical properties, solar selective coatings enhance the thermal efficiency of solar photothermal converters. Hence it seems to be interesting to study the optical properties of promising materials as solar selective coatings. In an earlier work, it was demonstrated that sol–gel deposited cobalt oxide thin films possess suitable optical properties as selective coatings. In this work, cobalt oxide thin films were prepared by same technique and their optical properties were analyzed as a function of the dipping time of the substrate in the sol, using the spectroscopy ellipsometry, atomic force microscopy and X-ray photoelectron spectroscopy techniques. The optical constants (n and k) for these films, in the 200–800 nm range, are reported as a function of the dipping time. The fitting of ellipsometric data, Is and Ic, for the glass substrate and the cobalt oxide thin film, as modeled with the Lorentz and Tauc–Lorentz dispersion relations, indicated that the film microstructure resembles a multilayer stack with voids. From these results, the Co3O4 and void percentages in the film were estimated. Both, thin film thickness and void/Co3O4 percentage ratio, were determined to be strongly dependent on the immersion time. Furthermore, the total thickness of a multilayered film was found to be the sum of thickness of each individual layer. 相似文献
77.
Anisotropy of thin opal films was studied by ellipsometric technique in a visible spectral range. At normal light incidence, the ellipsometric data were directly related to anisotropy parameters measured by polarization modulation technique. In the (111)-oriented thin films, the optical anisotropy was mainly caused by internal strain-induced birefringence with anisotropy axes oriented along [110] and [-112] directions. The deviation from 180°-symmetry, which has been observed for ellipsometric parameters in the in-plane sample rotation experiments at normal incidence, was enhanced at oblique incidence and assigned to particular properties of opal. Experimental data were discussed in the model of stacked anisotropic layers. 相似文献
78.
We present an optical, non-destructive, non-contact method of determining the silicon homojunction epilayer free-charge carrier concentration profile and thickness by means of combined terahertz (0.2-1 THz) and mid-infrared (10-50 THz) spectroscopic ellipsometry investigation. A dual homojunction iso- and aniso-type silicon sample is investigated. Application of analytical models for iso-type and aniso-type homojunctions results in an excellent match between calculated and experimental data. Best-match model calculated parameters are found to be consistent with electrical spreading resistance epilayer thickness and resistivity values. 相似文献
79.
Accurate spectroellipsometric (SE) measurements in the rotating analyzer (RAE) or rotating polarizer (RPE) configurations require accurate values of the polarizer/analyzer(/retarder) azimuths. While the readings are usually fairly accurate, true values are influenced by possible offsets between the plane of incidence, physical axes of the elements, and the instrument scales. The offsets are often determined by specialized calibration procedures. We describe SE measurements designed to obtain the calibration parameters together with the target ellipsometric spectra. We use multiple settings of the polarizer (analyzer) azimuths in RAE (RPE), respectively, to optimize precision and accuracy of SE measurements, and to economize measurement time. The optimization concerns the choice of measurement parameters as well as the subsequent data analysis. We present in detail examples of visible-ultraviolet measurements. 相似文献
80.
T. Böntgen S. SchöcheR. Schmidt-Grund C. SturmM. Brandt H. HochmuthM. Lorenz M. Grundmann 《Thin solid films》2011,519(9):2933-2935
We report electro-optical measurements of BaTiO3/ZnO heterostructures grown by pulsed laser deposition. The optical properties of the heterostructures were examined with and without an applied bias. A change in the heterostructure optical properties is found and attributed to a linear electro-optical effect causing a change in the band gap. Moreover the formation of an electric polarization in the BaTiO3 layer causes a remanent change in the dielectric function if the bias is removed. The change could be estimated to be around 5 meV. 相似文献