Chemical interaction of CdTe and Cd1? x Zn x single crystals with aqueous H2O2 + HBr + Citric acid solutions

The chemical etching of single crystals of CdTe and Cd_1−x Zn _x Te solid solutions in bromine-evolving aqueous H₂O₂ + HBr + citric acid solutions is considered. Simplex design of experiments is used to construct the projections of etching rate isosurfaces and to map the polishing and nonpolishing composition regions. Dissolution in the polishing etchants is diffusion-controlled. As the zinc content of Cd_1−x Zn _x Te is raised, the etching rate increases; the boundaries of the polishing region do not change to any significant extent. The polish composition and the dynamic chemical polishing conditions are optimized for the semiconductors examined. Original Russian Text ? Z.F. Tomashik, I.I. Gnativ, V.N. Tomashik, I.B. Stratiichuk, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 7, pp. 1234–1238.     

Chemical etching of Cd<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Mn<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>Te solid solution single crystals with iodine solutions in methanol

Chemical etching of Cd_{1 ? x} Mn _x Te (0.04 < x < 0.5) solid solution (ss) single crystals in I₂ + CH₃OH etching mixtures was studied. Concentration and kinetic curves of etching rates were plotted. As the manganese concentration of the solid solution increases, the rates of their etching by iodine-methanol etchants increase, too. The etchant compositions and chemical-dynamic polishing protocols for Cd_{1 ? x} Mn _x Te single crystals were optimized.     

Chemical etching of CdxHg1-x Te single crystals in bromine-releasing aqueous H2O2-HBr-solvent solutions

The nature and mechanism of dissolution of single crystals of a Cd_0.21Hg_0.79Te solid solution in H₂O₂-HBr-solvent bromine-releasing aqueous solutions were determined, with water, ethylene glycol, and tartaric, citric, and lactic acids used as solvents. Projections of the surfaces of equal etching rates were constructed and the concentration limits were found for solutions that can be used for chemical-dynamical polishing of the surface of Cd_0.21Hg_0.79Te single crystals.     

Specifics of chemical etching of PbTe and Pb1 − x Sn x Te single crystals with I2-DMF solutions

The physicochemical interactions of Pb_{1 ? x} Sn _x Te solid solution and PbTe single crystals with I₂-DMF solutions were studied under reproducible hydrodynamic conditions for the first time. Their dissolution rates were investigated as dependent on the etchant components ratio and the temperature and stirring of etching blends, and the effect of the composition of solid solutions on the parameters of chemical etching was studied. Etchant compositions and the chemicodynamical polishing regimes for the studied single crystals were optimized.     

硫化锌镉固溶体光催化分解水产氢研究现状

硫化锌镉（Cd_1-xZn_xS,0 < x < 1）固溶体因其优异的活性、可调谐的能带结构在光催化分解水制氢领域备受关注,但其较快的光生电荷复合速率和光腐蚀仍阻碍了其进一步应用。因此,研究者们针对其固有缺陷进行了大量改性工作。我们首先简述了光催化反应热力学与动力学特征,随后详细综述了近年来Cd_1-xZn_xS在光解水制氢领域的研究进展,包括其结构调控、异质结构建、杂原子掺杂等方面,简要分析了Cd_1-xZn_xS光催化分解水所面临的挑战和问题,并对近期研究进行了展望。     

Photocatalytic hydrogen generation using glucose as electron donor over Pt/Cd x Zn1−x S solid solutions

Cd _x Zn_1?x S solid solution photocatalysts were prepared by a hydrothermal process. The photocatalysts were characterized by X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), and transmission electron microscope (TEM) measurements. Using glucose as an electron donor, photocatalytic hydrogen generation over Pt/Cd _x Zn_1?x S was investigated. The results show that glucose not only improves the efficiency of photocatalytic hydrogen generation but prevents photocorrosion of Cd _x Zn_1?x S. Glucose was degraded effectively with the hydrogen generation. The factors which affect photocatalytic hydrogen generation, such as composition and structure of Cd _x Zn_1?x S solid solutions, irradiation time, initial concentration of the glucose, and concentration of NaOH were studied.     

Electrochemical formation and composition analysis of Zn x Cd1-x Se solid solutions

The direct growth of ZnSe–CdSe solid solution onto metallic cathodes by electrodeposition from acidic aqueous sulphate solutions is described. The plating process is studied by simple voltammetry, while the structure and composition of the electrolytic deposits are investigated by X-ray diffraction. The experimental d-spacing values of the as-grown mixed lattice are compared to data from reference Zn _x Cd_1-x Se pellets of standard composition, produced by a sintering method. The findings are supplemented with energy-dispersive X-ray (EDX) elemental analysis. Thereupon, the variation of the mole fraction x in Zn _x Cd_1-x Se, and the solid phase constitution of the electrodeposits are determined and correlated to the electrochemical conditions of growth. The resulting films contain admixtures of CdSe compound and metallic Cd.     

Impurity and phase compositions of the surface of CdxHg1?xTe solid solutions

The results of our studies of the real surface impurity and phase compositions of Cd _x Hg_{1 − x} Te solid solutions and changes in the compositions induced by thermal evacuation and ion bombardment are presented. The impurity and phase compositions of the surface of CdHgTe solid solutions exposed to air included the gases and vapors (CO, O₂, H₂O) and hydrocarbons adsorbed from the atmosphere. Thermal vacuum treatment of the samples at 615 K led to surface purification from organic impurities, oxygen, water, and mercury microinclusions. The Cd _x Hg_{1 − x} Te sample surface was completely cleaned and its stoichiometric composition achieved by ion etching to a depth of 100 ?.     

Spin glasses in CdCr2S4-ZnCr2S4 solid solutions

Magnetic properties of the continuous series of the solid solutions formed by the ferromagnet CdCr₂S₄ and antiferromagnet ZnCr₂S₄ compounds have been studied. The concentration and temperature boundaries of the magnetically active phases coexisting in the Cd_{1 ? x} Zn _x Cr₂S₄ system have been determined. It has been established that the ferromagnetic samples based on CdCr₂S₄ lie in the interval of concentrations 0 < x < 0.20, and the antiferromagnetic samples based on ZnCr₂S₄ are located in the interval of 0.9 < x < 1.0. The widest concentration interval (0.2 < x < 0.9) corresponds to spin glasses. The results obtained are discussed based on the percolation model.     

First-principles calculations of Cd-doped ZnO thin films deposited by pulse laser deposition

Zn_1−xCd_xO thin films are deposited on quartz substrate by pulse laser deposition. Their band structure and optical properties are experimentally and theoretically investigated. By varying Cd concentration, the band gap of Zn_1−xCd_xO films can be adjusted in a wide range from 3.219 eV for ZnO to 2.197 eV for Zn_0.5Cd_0.5O, which produces different emissions from ultraviolet to Kelly light in their photoluminescence spectra. Simultaneity, the electronic structure and band gap of Zn_1−xCd_xO are investigated by the density functional theory (DFT) with a combined generalized gradient approximation (GGA) plus Hubbard U approach, which precisely predicts the band-gaps of ZnO and Zn_1−xCd_xO alloys. Both the experimental results and theoretical simulation reveal that with increasing Cd concentration in Zn_1−xCd_xO alloys, their absorption coefficients in visible light range are evidently enhanced. The adjustable photoluminescence emission and enhanced visible light absorption endow Zn_1−xCd_xO alloys potential applications in optoelectronic and photocatalytic fields.     

The diffusion kinetics in isothermal epitaxy of Cd<Subscript>x</Subscript>Hg<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>Te solid solutions from an unlimited liquid phase volume

The kinetics of liquid phase epitaxy of Cd_xHg_{1 ? x} Te solid solutions was analyzed in terms of the concept of diffusion-controlled crystallization. The boundary conditions for the boundary-value diffusion mass transfer problem were obtained on the assumption of phase equilibrium at the interface, when component concentrations are coupled by phase equilibrium equations written in terms of the polyassociative solutions model. The thermodynamic model developed for the growth process allowed us to describe the conditions of solid solution growth and predict conditions for the preparation of Cd-Hg-Te layers of the required composition.     

Solubility of cadmium in lead tellurides

The solubility of cadmium in PbTe was determined using microhardness and hydrostatic density measurements and by electron microscopy and electron probe microanalysis. All these methods indicate that the existence region of Pb_{1 − x} Cd _x Te solid solutions (ss) extends to x = 0.08 at 670°C. As the cadmium concentration of the solid solution increases, microhardness shifts up, whereas density shifts down.     

Multifractal parameterization of space forms on surfaces of Zn x Cd1 − x Te-Si(111) heterocompositions and its relationship to the conditions of layer synthesis

Multifractal (MF) analysis of space forms on the surfaces of thin layers of Zn _x Cd_{1 ? x} Te solid solution precipitated onto a Si(111) substrate via the hot wall approach is performed. AFM images of film surfaces are used for MF analysis. The parameters of MF spectra are determined for the film surfaces of the above system. It is shown that the MF functions of system correspond to their canonical forms, and the resulting computational procedure can be applied to describe and analyze the state of spatial fractal structures that form on a layer’s surface. The quantitative relationships between the parameters of the MF spectrum of a film’s surface and its conditions of precipitation are revealed.     

Phase equilibria in the ZnGeAs2-CdGeAs2 system

The phase diagram of the ZnGeAs₂-CdGeAs₂ system was constructed using a set of physicochemical analysis methods (X-ray powder diffraction, differential thermal, and microstructural analyses). It was shown that there is a continuous series of solid solutions Zn _x Cd_{1 ? x} GeAs₂ in the system at temperatures above 600°C. At temperatures below 600°C, there is a significant phase separation region. The solubility at room temperature on the side of ZnGeAs₂ does not exceed 12 mol % CdGeAs₂, and that on the side of CdGeAs₂ is no more than 16 mol % ZnGeAs₂. The change in the crystal lattice parameters of the solid solutions within these concentration ranges obeys Vegard’s law, which is indicative of the mutual replacement of Zn and Cd in the cation sublattice of the compounds ZnGeAs₂ and CdGeAs₂.     

Synthesis and optical absorption property of the Zn2TixSn1−xO4 (0?x?1) solid solutions

Zn₂Ti_xSn_1−xO₄ (0?x?1) solid solutions with an inverse spinel structure (Fd3m) were synthesized by solid-state reactions at 1300°C of the stoichiometric mixtures of ZnO, TiO₂ and SnO₂. X-ray diffraction, thermogravimetric and differential thermal analyses, scanning electron microscopy, transmission electron microscopy and BET specific surface area measurements were used to gain insights into the solid-state reactions and phase transformation of the system. Optical absorption property of the Zn₂Ti_xSn_1−xO₄ (0?x?1) solid solutions was studied with the ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis DRS). The Zn₂Ti_xSn_1−xO₄ (0?x?1) solid solutions showed optical absorptions of the semiconductors in the near ultraviolet region; the adsorption band shifts with the composition of the solid solution.     

Lithium-cationic conductivity in the Li4 − 2x Cd x GeO4 system

The lithium-conducting solid electrolytes in the Li_{4 ? 2x} Cd _x GeO₄ (0 ≤ x ≤ 0.6) system are synthesized. Their crystal structure and temperature and concentration dependences of conductivity are studied. The specimens with the highest conductivity have a γ-Li₃PO₄-derivative structure. The solid solutions with x = 0.15–0.25 are stable at the room temperature, whereas the specimens with x ≥ 0.3 decompose yielding Li₂CdGeO₄ below 310 ± 10°C. Li_3.6Cd_0.2GeO₄ solid solution exhibits the highest conductivity (5.25 × 10^?2 S cm^?1 at 300°C). The factors, which affect the conductivity of synthesized solid electrolytes, are considered.     

A novel electrochemical deposition route for the preparation of Zn1−xCdxO nanorods with controllable optical properties

Here we explored a novel and facile electrochemical route for the preparation of Zn_1?xCd_xO (x is atomic percentage of Cd) nanorods with controllable optical properties. The Zn_1?xCd_xO nanorods can be routinely obtained when the electrochemical deposition was carried out in solution of Zn(NO₃)₂ + Cd(NO₃)₂ + citric acid at ?1.0 V (vs SCE). EDS results demonstrated that Cd, Zn, and O elements existed in the deposits, and ternary Zn_1?xCd_xO compounds were obtained. XRD results showed that Zn_1?xCd_xO nanorods were pure ZnO wurtzite structures. HRTEM and SAED analyses confirmed that Zn_1?xCd_xO nanorods were single-crystalline. The optical properties of Zn_1?xCd_xO nanorods were investigated in this paper.     

Phase diagrams in the quaternary systems M1−xCuxCr2X4 with M = Cd,Mn, and X = S,Se

The phase diagrams of the spinel systems Cd_1?xCu_xCr₂S₄, Cd_1?xCu_xCr₂Se₄, and Mn_1?xCu_xCr₂S₄ have been studied on the basis of X-ray powder photographs of quenched samples and high-temperature X-ray diffraction patterns. At room temperature the mutual solid solubilities of the metallic copper and the semiconducting cadmium and manganese spinels are only small (x < 0.05 and >0.95). The interchangeability, however, increases largely with increasing temperature. Complete series of mixed crystals, as in the Zn_1?xCu_xCr₂X₄ (X = S, Se) systems, however, are not formed. The solid solutions with x > 0.07 and <0.95, x > 0.095 and <0.90, and x > 0.36 and <0.87, respectively, formed at higher temperatures cannot be quenched to room temperature without decomposition. The unit cell dimensions of the spinel solid solutions studied obviously do not obey Vegard's rule.     

Fluctuation in occupancy of Cu2+ ions in Zn- and Cd-substituted Cu-ferrites

Mössbauer effect technique has been used for the comparative study of Cu_1?x Zn _x Fe₂O₄ and Cu_1?x Cd _x Fe₂O₄ ( _x = 0.0?1.0) ferrites. Both Zn²⁺ and Cd²⁺ cations are divalent, non-magnetic ions with different ionic radii. With the substitution of these non-magnetic cations the average internal magnetic field decreases and paramagnetic behavior is dominated at x = 0.7 in both series. It is observed that the occupancy of Cu²⁺ ions for tetrahedral site is not constant for all compositions but fluctuate between 8–15%. It is also found that Cu²⁺ ions have more preference for tetrahedral site in Cu-Zn system as compared to the Cu-Cd system. Zn²⁺ and Cd²⁺ both ions occupy tetrahedral site completely and form normal spinels for x = 1.0.     

Phase relationships of the lithium halide spinels Li2MCl4-Li2MBr4 with M = Mn,Fe, Cd

The sections Li₂MCl_4?4xBr_4x of the quaternary systems LiCl-LiBr-MCl₂-MBr₂ with M = Mn, Cd, and Fe were studied by high-temperature X-ray diffraction patterns and DTA and DSC measurements. In the quasibinary lithium manganese halide system complete series of solid solutions exist between the inverse spinels Li₂MnCl₄ and Li₂MnBr₄. Li₂MnBr₄ and solid solutions with x > 0.54 undergo phase transitions to tetragonal spinels at lower temperatures. In the nonquasibinary system with M = Cd, only at temperatures near 400°C a complete series of mixed crystals is formed. At lower temperatures the system is mainly two-phase with rock salt-type Li_1?yCd_0.5yCl_1?xBr_x and cadmium chloride-type Cd_1?yLi_2yCl_2?2xBr_2x solid solutions in equilibrium. The lithium iron halide system is similar to that of cadmium, but spinel-type Li₂FeBr₄ does not exist at any temperature. The manganese and cadmium halide spinels and spinel solid solutions undergo phase transitions to NaCl defect structures at elevated temperatures.