X-ray investigations on the defect structure of KCl with Cd++ impurities

A systematic defect characterization by X-ray diffraction was carried out on crystalline KCl system with Cd⁺⁺ impurities at various levels, viz. 2, 4, 6, 8, and 10 mole%. Quantitative estimation of the amount and nature of defects was done from the integrated X-ray intensity measurements of the samples. Further analyses of the experimental data indicate enhancement of the Debye-Waller factor with concentration of Cd⁺⁺ impurities. The measured density and the cell constant values at room temperature yield vacancy estimations for the system. The observed change of Bravais lattice of the system for Cd⁺⁺ concentrations from 4 mole% with appreciable enhancement of intensity of Bragg reflections of mixed indices are reported and discussed.     

Effect of quenching rate and annealing on ESR of Cu2+ and γ-induced Cd+ in low alkali borate glasses

A new ESR hyperfine structure (hfs) of Cu²⁺ was detected in moderately (cooling rate ≈ 3 K/s) and rapidly (10³–10⁵K/s) quenched borate glasses with Na₂O content smaller than 5 mol% in addition to the already reported three patterns, spectra I, II and III, for the moderately quenched borate glasses with 5 ? [Na₂O]?13, 20 ? [Na₂O] ?37 and 55 ? [Na₂O] ? 75, respectively. The ESR parameters of this spectrum were much the same as those of II, but a significant difference was observed between thermal stabilities of these spectra. The newly observed spectrum was named spectrum II′. A superposition of spectra II′ and I was seen in low alkali borate glasses ([Na₂O] ? 5 mol%). The relative intensity of II′ to I increased remarkably with increasing quenching rate of the melts and with decreasing alkali content under the same quenching condition. In addition, spectrum II′ was found to relax into I upon thermal annealing of the glasses. Similar changes were observed also in ESR of the γ-induced Cd⁺ with 5s¹ electronic configuration. A tentative model to account for the spectral changes was proposed on the basis of the characteristics of B—O bonding.     

Explanations of the optical absorption and ESR spectrum for tetragonal Ni+ centers in CuAlS2:Ni+ crystals

In this paper, the optical absorption and electron spin resonance (ESR) spectrum of Ni⁺‐doped CuAlS₂ crystals have been studied by using a double spin‐orbit (SO) coupling approximation model, where the effects due to the SO coupling of the central metal 3d¹ ion and those of ligands are included. From this model, the formulas of the ESR g factors g_‖, g_⊥ and hyperfine structure constants A_‖, A_⊥ for 3d¹ ions in the tetragonal MX₄ clusters are constructed. The optical absorption and ESR parameters for Cu⁺ sites of CuAlS₂ have been calculated. The results obtained show that Ni⁺ ions substitute for Cu⁺ ions sites. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of annealing and composition on crystal structure,surface morphology and optical absorption of chemically deposited Cd1‐xSnxS films

Cd_1‐xSn_xS thin films were successfully deposited on suitably cleaned glass substrate by chemical bath deposition method at 74 °C. Hydrated Stannous Chloride (SnCl₂.2H₂O) in aqueous solution was added to the CdS growing solution in different proportions. The experimental results indicate, a successful doping for lower concentration of Sn, saturation for intermediate doping levels, and a degradation of the doping process for higher concentration of Sn. Indirect (X‐ray diffraction) and Direct (Scanning electron microscopy) measurements were performed to characterize the growth and the nature of crystallinity of the different Cd_1‐xSn_xS films. The effect of annealing on the crystal structure and morphology of the deposited films has also been discussed. The X‐ray diffraction spectra show that the thin films are polycrystalline and have both cubic and hexagonal structure. The Interplanar spacing, lattice constant, grain size, strain, and dislocation density were calculated for as‐deposited and annealed films. The grain size was found to decrease from 5 nm to 0.89 nm with doping concentration of Sn. The grain size further decreased due to annealing at 400 °C. SEM studies show layered growth and long needle like structures along with some voids. After annealing the densification and smaller size of the particles was also observed. The optical absorption spectra show shifting of absorption peaks towards lower wavelength side (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Effect of temperature gradient on the lamellar structure formation

The detailed definition of interplay between interface curvature and concentration field is presented. It explains an effect of horizontal component of temperature gradient on the lamellar structure formation during the steady-state eutectic growth. This definition is composed of two competitive terms connected with the heat and matter transfers, respectively. The above competition is interpreted by using the thermodynamics of irreversible processes. Finally, it is shown that the lamellar spacing depends on both the growth rate and temperature gradient for a given regular eutectic solidifying under stationary conditions. The proposed analysis is the fourth part of model developing in “Crystal Research and Technology” which is mentioned in the References.     

Na+对KDP晶体生长的影响

本文利用传统的降温法和"点籽晶"快速生长法在不同Na+掺杂浓度的溶液中生长KDP晶体,定量研究了Na+对KDP晶体生长的影响.实验发现:Na+的存在降低了溶液的稳定性,致使KDP晶体柱面容易扩展.Na+的存在对KDP晶体的光学性能基本没有影响.     

Cd对纤锌矿ZnO极化特性的影响以及Zn0.75Cd0.25O/ZnO界面能带偏差的第一性原理研究

基于第一性原理GGA+U方法研究了Zn1-xCdxO合金的品格常数以及自发极化随Cd组分x的变化关系,其中极化特性的计算采用Berry-phase方法,同时计算了禁带宽度随Cd组分x的变化关系,并得到了能隙弯曲参数0.69.此外,通过计算宏观平均静电势的方法得到了(5 +3)Cd0.25Cd0.750/ZnO超晶格界面处的价带偏差为0.13 eV,导带偏差与价带偏差的比值为4/13,并且Zn1-xCdxO/ZnO界面两侧能带呈现Ⅰ型排列,这些研究结果将对Zn1-xCdxO/ZnO界面二维电子气的设计与优化起到重要作用.     

Structural and thermal properties of Zn2+-, Cd2+-, and Hg2+ forms of zeolite X

The exchange of Zn²⁺, Cd²⁺ and Hg²⁺ with zeolite NaX has been studied. The influence of the above cations on crystalline structure of zeolite X and its thermal stability has been shown on the grounds of X-ray diffraction, differential thermal analysis and infrared spectroscopic measurements.     

Effect of hydrogen peroxide on hydrofluoric acid etching of high-k materials: ESR investigations

Oxides and silicates of zirconium and hafnium are being actively considered for use as gate dielectrics in MOS devices. Because of their higher dielectric constant (k ∼ 16-22), they permit the use of thicker layers without sacrificing the capacitance value. Wet chemical etching is the method of choice for patterning these oxides. The etching process has to be selective to zirconium/hafnium oxides over silicon dioxide, which may be present in other areas. In this paper, work done on HF etching of ZrO₂ and HfO₂ in presence of hydrogen peroxide is presented and discussed. It was found that addition of hydrogen peroxide to HF solutions lower the etch rate of ZrO₂ and HfO₂ films. Electron spin resonance (ESR) spectroscopy was used to probe the reasons for the decrease in etch rates in this solution.     

Epitaxy of Cd on muscovite

Cd is deposited on air cleaved and annealed muscovite. The Cd films were seeded by Ag. Then Cd grows epitaxially with its (0001)-planes parallel to the (001)-plane of muscovite.     

Ba2+对 YVO4:Dy3+荧光粉发光性能的影响

用化学共沉淀法制备了 Y0.99-xBaxVO4:1; Dy3+荧光粉,研究了 Ba2+浓度(0≤x≤0.25)及电荷补偿剂 K+对荧光粉发光强度的影响.结果表明:在315 nm 紫外光激发下,随Ba2+浓度的增加,Y0.99-xBaxVO4:1;Dy3+荧光粉发光强度呈现先增加后降低的趋势,在x=0.1 处达最大值,与未添加 Ba2+的荧光粉相比发光强度提高约50;,但色坐标变化不明显,色温在5200 K 左右,为光色柔和的暖白光.电荷补偿剂 K+的添加使 Y0.99-xBaxVO4:1;Dy3+荧光粉在 Y0.99-x BaxKxVO4:1;Dy3+荧光粉发光强度的基础上明显提高,色坐标及色温变化不明显.     

Effect of buffer layers on the dislocation structure of heteroepitaxial systems

Transmission electron microscopy (TEM) as well as X-ray topography (XRT) and X-ray diffractometry have been used for investigation of the structure of the LPE heteroepitaxial system In_0.05Ga_0.95As-In_yGa_1−yAs_1−xP_x-GaAs(111) A. A critical value of the lattice misfit has been shown to exist at the metallurgical boundary ((Δa/a)* ≈ 10⁻³) which results in the change of the film nucleation and growth mechanism as well as the change of misfit dislocations (MDs) generation mechanism. With (Δa/a)₀ > (Δa/a)* the nucleation and growth mechanism is mixed: island growth at the first stages of growth and layer-by-layer growth at large thicknesses. MDs are created in an “island film” developing a non-ordered dislocation network. The density of threading dislocations (N_d) is ∼ 10⁸ cm⁻². With (Δa/a)₀ < (Δa/a)* there is layer-by-layer mechanism of film's nucleation and growth from the very first stages of crystallization. MDs are injected into continuous layer along the inclined slip planes {111}, thus forming a regular three-dimensional grid of MDs. N_d is less than 10⁶ cm⁻² in the case. A model of dislocation structure formation in heterolayers has been proposed. Within the frame of this model the two critical values of phosphorus concentration in the quaternary melt have been quantitatively determined. These are corresponding to the change of MD generation mechanism. The expected values of N_d for (Δa/a)₀ > (Δa/a)* and (Δa/a)₀ < (Δa/a)* have been theoretically determined.     

Cd掺杂对Zn1-xCdxS:Cu能带结构和光电子瞬态过程的影响

本文采用高温固相反应法制备了Zn1-xCdxS:Cu黄色电致发光材料.研究了Cd含量对电致发光亮度、发光光谱、光生电子瞬态过程和热释光的影响.通过调整Cd含量,可以制备出黄色电致发光材料.研究发现Cd掺杂会使材料的电子陷阱密度减小,且使光生电子瞬态过程缩短.     

Effect of temperature on the structure of liquid In20Sn80

X-ray diffraction, density and dynamic viscosity measurements on liquid In₂₀Sn₈₀ have been carried out between 300 and 800 °C. An effect of temperature on the atomic structure of molten In₂₀Sn₈₀ is discussed in terms of the model of inhomogeneous structure. It is shown that the structure of liquid In₂₀Sn₈₀ can be presented by atomic clusters with stable composition and atomic packing and a portion of free atoms with higher mobility. The number and the size of clusters decrease and the volume fraction of free atoms increases under heating.     

Effect of synthesis conditions on the fractal structure of yttrium-stabilized zirconium dioxide

The effect of synthesis conditions (sequential precipitation, coprecipitation, and sol–gel method) on the fractal structure of yttrium-stabilized zirconium dioxide has been investigated. It has been shown that the difference between methods manifests itself clearly in xerogel nanostructures, viz. by the number of fractal aggregation levels (three levels in hydroxide precipitates and two in sol–gel) and the absence of mass-fractal aggregation in sol–gel. It is been determined that the mass-fractal aggregation of precursors contributes to good filtration of hydroxide precipitates and allows preparation of oxides with soft, readily destructible aggregates, and that surface-fractal aggregation makes for good pressability of oxides.     

Effect of Nd3+ on the growth and quality of KDP crystals

KDP crystals were rapidly grown from solutions doped with different Nd³⁺ concentrations. During the growth process, “foggy” inclusions were selectively captured in the pyramidal sector of KDP crystal and hourglass shaped crystals were obtained. It is found that the nonuniform distribution of Nd³⁺ ions causes remarkable differences in optical quality between prismatic and pyramidal sectors. With increasing Nd³⁺ concentration, the optical quality is greatly decreased for pyramidal sectors, while the change is not so obvious for prismatic sectors. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Fe3+对KDP晶体光学质量的影响

金属离子Fe3+对KDP晶体的生长和光学性质有明显影响.本文在前期研究的基础上[1]系统考察了该杂质离子对KDP晶体光学质量的影响.实验结果表明,三价金属离子Fe3+会降低KDP晶体的透光率,同时对晶体均匀性和光损伤阈值也有明显影响.光损伤阈值降低的主要原因在于杂质诱发缺陷导致的电子崩电离、多光子电离(尤其是双光子电离)等过程的发生.