Photosensitive Centers in CdTe〈Ge〉, CdTe〈Sn〉, and CdTe〈Pb〉

The spectral and temperature dependences of photoconductivity in CdTePb crystals under band-gap and combined excitation were studied at photon energies in the range 0.53–1.7 eV and temperatures from 80 to 300 K. The high photosensitivity of the crystals and the observed IR and temperature quenching of photoconductivity indicate that, just as in CdTeGe and CdTeSn, the recombination processes in CdTePb are dominated by deep centers with drastically different capture cross sections for electrons and holes. Some parameters of the centers are determined. The results suggest that the likely defect species responsible for the high photosensitivity of CdTePb is an acceptor complex consisting of a Cd vacancy and a metal (Ge, Sn, Pb) ion on the Cd site: (V ^2– _CdM⁺)^–/0.     

Magnetic Properties of High-Resistivity CdTe〈In〉 and CdTe〈Cl〉 Crystals

The magnetic susceptibility of high-resistivity CdTeIn and CdTeCl crystals was measured between 4.2 and 300 K. The susceptibility was found to vary anomalously with temperature. Below 50 K, all the samples were paramagnetic. The observed anomalies are interpreted in terms of donor–acceptor pairs formed by native defects and dopant or uncontrolled impurity atoms. The effect of doping on the 300-K is related to the Van Vleck paramagnetic contribution resulting from the local electric fields of X_i–V _Cdand In_i–V _Cddefect complexes. In CdTeCl, this contribution is insignificant.     

Dopant microassociation mechanisms in Si〈Mn〉 and Si〈Ni〉

This paper examines the mechanisms underlying the formation of Mn and Ni impurity microassociates in Si. Thermodynamic analysis of Si??Mn?? and Si??Ni?? suggests that the formation of various types of microassociates is mainly due to internal Coulomb forces. Theoretical models for the formation of microassociates adequately describe impurity microassociates revealed in silicon by IR microscopy, X-ray diffraction, and electron probe microanalysis.     

Formation energies of native point defects in II–VI crystals

The formation energies of point defects in II–VI crystals have been evaluated from Hall measurement results and calculated by a thermodynamic method and the extended Hückel method. The energies obtained by different techniques are in satisfactory agreement with each other and with data in the literature.     

Influence of yttrium on microstructure and point defects in α-Al2O3 in relation to oxidation

Although the influence of yttrium on transport properties of alumina has been the object of many studies, the mechanisms by which this element acts have not yet been elucidated. The method of modification by yttrium of the microstructure of polycrystalline alumina and the nature of the point defects created by this doping element were studied. The results obtained are discussed in relation to alumina transport properties and especially in relation with the effect of yttrium on the oxidation mechanism of alumina former alloys, taking into account the doping amount.     

The plastic behaviour of 〈100〉 and 〈111〉 textured polycrystalline metals during simultaneous torsion and extension

On the basis of computer-calculated yield functions, the work hardening of 100 textured Cu-0.64 at % Co-0.48 at % Si and 111 textured polycrystalline copper wires were studied by simultaneous torsion and extension and by pure extension. Representing the work hardening by resolved shear stress-resolved shear strain curves, the rate of hardening is significantly lower for torsion than for pure extension. This behaviour is explained by the operation of different slip systems activated in the two modes of deformation. In the 100 textured Cu-Co-Si wires, heterogeneous plastic deformation was observed beyond about 80% shear strain.     

Thermodynamic modeling and preparation of hafnium carbide coatings in the hafnium–carbon–fluorine system

Thermodynamic modeling of the Hf–C–F system has been carried out in wide temperature and pressure ranges. Analysis of the calculated molecular composition of the vapor phase in equilibrium with Hf + HfC and the vapor phase in equilibrium with C + HfC has shown that the chemical vapor transport of hafnium under isothermal conditions is mediated by lower hafnium fluorides. The content of the lower hafnium fluorides increases with increasing temperature and decreasing total pressure in the system. Reactive hafnium carbide deposition on a carbon material, with CF₄ as a transport agent, has been studied experimentally. The coating obtained in this way is sufficiently dense and consists of hafnium carbide nanocrystals ranging in size from 100 to 200 nm.     

Etching behavior of CdTe,CdTe〈Ge〉, CdTe〈Sn〉, and CdTe〈Pb〉 single crystals in aqueous (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript>-HBr-citric acid solutions

We have studied the dissolution behavior of undoped and Group IV (Ge, Sn, and Pb) doped cadmium telluride single crystals in aqueous (NH₄)₂Cr₂O₇-HBr-citric acid solutions, constructed dissolution rate-etchant composition diagrams, and located the composition regions of polishing, selective, and non-polishing solutions. The doping effect on the chemical etching process has been examined, and the rate-limiting steps in the chemical dissolution of the materials studied have been identified. We have assessed the surface condition of the etched crystals by microstructural analysis and surface profilometry and optimized the etchant composition for the dynamic chemical polishing of these semiconductors.     

Thermodynamic modeling of oxygen dissolution in uranium mononitride at 900–1400 K

Thermodynamic modeling of oxygen dissolution in uranium mononitride in relation to temperature showed that the solubility limit of oxygen in uranium mononitride monotonically increases from 0.0008 to 0.0092 at. % as the temperature is increased from 900 to 1400 K. The presence of a carbon impurity increases the oxygen solubility in uranium mononitride by a factor of 4–5. The oxygen solubility increases by 20–30% as the stoichiometric coefficient in uranium mononitride containing a carbon impurity is decreased by 0.005.     

Differing behaviors of point defects in Fe–36Ni alloy during annealing after low-temperature deformation and irradiation

Fe–36Ni alloy is studied in states in which it is quenched, irradiated with electrons at 70 K, and deformed at 77 K. It is shown that similar structure-phase transformations occur in the investigated alloy during annealing at the temperature range of 70–570 K both after preliminary low-temperature electron irradiation and after preliminary low-temperature deformation. Migration of interstitial atoms (70–140 K) and vacancies (180–570 K), which induce phase transformations and are the results of atomic separation and ordering of zones with increased nickel content, is observed. Mechanisms of structure-phase changes under deformation and annealing are discussed.     

Synthesis and properties of homogeneously doped Nb2O5〈Dy〉 and a LiNbO3〈Dy〉growth charge

We have studied conditions for the synthesis of niobium pentoxide and a lithium niobate growth charge doped with dysprosium, which was added to niobium hydroxide obtained through extraction processing of rare-metal-containing raw materials. The phase composition of Nb₂O₅〈Dy〉 precursors was determined by X-ray diffraction and IR spectroscopy. Using inductively coupled plasma mass spectrometry in combination with a laser ablation sampling system, we examined the Dy dopant profile in Nb₂O₅ powder samples and the LiNbO₃ growth charge. The Nb₂O₅ precursors and the growth charge synthesized using them were shown to be chemically uniform in composition. The present results are of importance for the growth of defect-free lithium niobate single crystals of optical quality, highly uniform in composition, with a predetermined doping level.     

Luminescence spectra and kinetics of LiF〈U〉-O crystals

The promising phosphor LiF〈U〉-O has been studied by nanosecond-resolution pulsed spectrometry. The uranium and oxygen luminescence buildup and decay characteristics have been measured at 300 K. The uranium luminescence buildup under nanosecond electron excitation has been shown to involve two steps. The effect of pulsed electron irradiation on the activator luminescence efficiency has been assessed.     

Co-yield surfaces for {111}〈110〉 slip and {111}〈112〉 twinning in fcc metals

The co-yield surfaces in fcc single crystals for slip on 11111110 and twinning on {111}112 systems have been analyzed and derived systematically for the first time. The results demonstrated that only if the ratio of the critical resolved shear stress (CRSS) for twinning to that for slip is within the range of , slip and twinning can occur together. There are only two types of co-yield surfaces when is within this range. The corresponding analytical expressions of all possible types of yield vertices are also derived and tabulated. One type consists of 259 co-yield stress states when , which can be classified into 21 groups in stress space according to the crystal symmetry. The other type contains 259 co-yield stress states also when , which can be subdivided into 19 groups. Of the two types of the co-yield stress states, 139 ones are common and 120 ones are different.     

Kinetics of silicides on Si〈100〉 and evaporated silicon substrates

We investigated the growth rates of Ni₂Si, NiSi, Pt₂Si, PtSi and CrSi₂ formed on a Si〈100〉 (Si^c) or an evaporated silicon (Si^e, which is amorphous) substrate during thermal annealing. The same phases of silicides were found on Si^c and Si^e. The growth rates of the silicides formed on Si^c were similar to those formed on Si^e. The formation temperature of CrSi₂ was about 50°C lower on Si^e than on Si^c, and the CrSi₂ film was laterally more uniform on Si^e than on Si^c. We summarize here the results of this and other investigations (e.g. Pd₂Si, Co₂Si, CoSi, CoSi₂, NiSi₂, TiSi₂, and ErSi₂) on the differences in the kinetics of silicides formed on the two substrate types.     

Stuey of Thermodynamic Properties of Nonstoichiometric Phase 〈Zr1—zCezO2—x〉 with Compound Energy Model

Using compound energy model (CEM), the thermodynamic properties of and were evaluated. The evaluation was based on the optimization of ZrO2-CeO2 and ZrO2-CeO1.5 systems, as well as the miscibility gap in CeO1.5-CeO2 system. Except the cubic fluorite structure phase assessed with compound energy model, all the other solution phases were assessed with subsitutional solution model. The model parameters were evaluated through fitting the selected experimental data by means of thermodynamic optimization. A set of parameters with thermodynamics self-consistency was obtained and satisfactorily described the complex relation between y in and the partial pressure of oxygen at different temperatures, also the interdependence among miscellaneous factors such as temperature, oxygen partial pressure, the reduction amount of CeO2 as well as the nonstoichiometry in cubic phase . The calculated results seem to be reasonable when put into the explanation of pressureless sintering of CeO2-stabilized ZrO2 powder compacts at a controlled oxygen partial pressure.     

Micromechanical properties of GaP〈Dy〉 epilayers

The physicomechanical properties of GaP epilayers grown by liquid phase epitaxy from indium-based high-temperature solutions have been studied using microindentation. The results demonstrate that the growth of GaP epilayers from indium-based high-temperature solutions leads to a reduction in their microhardness, microbrittleness, and fracture toughness. The addition of a rare-earth dopant to a high-temperature solution has an ambiguous effect on the strength of the epilayers. Low rare-earth concentrations may both reduce and increase the microhardness of the epilayers, depending on epitaxy conditions. The random microhardness distribution of samples containing rare-earth inclusions has two peaks: one due to the rareearth inclusions, and the other due to the region with a relatively low lanthanide concentration.     

The activation of 〈c + a〉 non-basal slip in Magnesium alloys

The activation of 〈c + a〉 non-basal slip system can help to improving the mechanical properties of Magnesium alloys. The activation conditions of 〈c + a〉 non-basal slip system in Mg alloys are reviewed, such as the addition of lithium elements, increasing temperatures, and regions of stress concentration, and so on. Moreover, the article summarizes our results from the work on Mg alloys using equal channel angle pressing with back pressure, and points out that 〈c + a〉 non-basal slip systems also become active much easier under hydrostatic pressure, which will help to open new window to explore the basic physics of the activation of non-basal slip.     

Temperature-gradient growth kinetics and macrodefects of GaInAs〈Bi〉/InAs heterostructures

Temperature-gradient growth of GaInAs〈Bi〉 layers on InAs substrates has been studied, and distribution coefficients in the Ga-In-As-Bi system have been determined. Data are presented on the influence of temperature, temperature gradient, and melt composition on the quality of the epilayers.     

Growth of large LiNbO3〈Mg〉 crystals

We have analyzed conditions for the growth of large (≥80 mm in diameter) LiNbO₃〈Mg〉 crystals in a wide range of dopant concentrations in the melt (2.9–5.8 mol % MgO). We have established conditions for the growth of large LiNbO₃〈Mg〉 crystals uniform in doping level from melts containing magnesium concentrations above a certain threshold (C _melt 5.0–5.8 mol % MgO) and optimized the high-temperature electrodiffusion annealing process, which allowed us to obtain single-domain, microstructurally homogeneous, large LiNbO₃〈Mg〉 crystals containing 4.9–5.15 mol % magnesium.     

Electric-field effect on the electrical conductivity of InSe and InSe〈Dy〉 crystals

We have studied the effect of external dc electric field on the dark conductivity $\left( {\sigma _{d_0 } } \right)$ of undoped and dysprosium-doped InSe single crystals having different initial dark conductivities ( $\sigma _{d_0 } = 2.5 \times 10^{ - 8}$ to 10^?2 S/cm at 77 K) and doping levels (～10^?5 to 10^?1 at % Dy, respectively). At T ≤ 200–220 K and E ≥ 80–150 V/cm, the σ_d of the high-resistivity ( $\sigma _{d_0 } < 10^{ - 4}$ S/cm) undoped and slightly doped (<10^?2 at % Dy) crystals increases with increasing external electric field. The observed σ_d(E) behavior is shown to be unrelated to electric-field-induced heating of charge carriers or other effects of a high electric field when carrier scattering by various point defects and phonons prevails. It is primary due to partial disorder in the crystals, the presence of drift barriers in their empty energy bands, and the influence of injection and doping levels on the dimensions of the barriers.