Impurity-dislocation Interaction Research Articles

Dislocation–impurity interaction in Czochralski-grown Si heavily doped with B and Ge

Dynamic interaction between dislocations and impurities in Si is investigated by using X-ray topography and the etch-pit technique from the viewpoint of Czochralski growth of Si crystals. Dislocation generation is effectively suppressed by doping of B and co-doping of B and Ge, which is originating in the immobilization of dislocations by preferential segregation of impurities. Dislocation velocity in motion is enhanced by increasing the concentration in B impurities. Change of the lattice parameter due to the impurity doping leads to the generation of misfit dislocations at the seed/crystal interface.

Dislocation–impurity interaction in Si

The dynamic interaction between dislocations and impurities B, P and Ge in Si with concentrations up to 2.5×10 20 cm −3 is investigated by the etch-pit technique, in comparison with that of O impurity in Si. Dislocation generation from a surface scratch is strongly suppressed when the concentration of B and P impurities exceeds 1×10 19 cm −3, originating from the immobilization by preferential impurity segregation. Dislocation velocity in motion enhances on increasing the concentration in B and P impurities. Neutral impurity Ge has weak effect on dislocation generation and velocity enhancement.

Microdefects and electrical uniformity of InP annealed in phosphorus and iron phosphide ambiances

Microdefects originating from impurity-dislocation interactions in undoped InP that had been annealed in phosphorus and iron phosphide ambiances have been studied using optical microscopy. The electrical uniformity of the annealed wafer is improved by removing impurity aggregation around dislocations and by eliminating impurity striations in the annealing process. Compared to as-grown Fe-doped semi-insulating (SI) material, SI wafers obtained by annealing undoped InP in iron phosphide ambiances have better uniformity. This is attributed to the avoidance of Fe aggregation around dislocations and dislocation clusters, Fe precipitation and impurity striations, and is related to the use of a low concentration of Fe in the annealed material. The influence of Fe diffusion on the migration of dislocations in the annealing process has been studied and reviewed.

Features of the low-temperature plasticity of Pb–In single crystals

The temperature dependence of the plasticity parameters of Pb–In single crystals with indium concentrations of 1–20 at. % are investigated under tensile deformation at a constant strain rate in the temperature interval 4.2–295 K. From an analysis of the experimental data, empirical estimates are obtained for the main parameters of the dislocation–impurity interaction and the dynamic drag coefficient of the dislocations. The calculated values of these parameters are consistent with the idea of a gradual transition on cooling, from a thermally activated motion of dislocations through local impurity barriers to a thermal–inertial motion. With increasing indium concentration (to 20 at. %) the low-temperature mechanisms of dislocation motion begin to be affected substantially by regions of short-range order (clusters), the presence of which is detected by the diffuse x-ray scattering method.

Electronic mechanism of impurity?dislocation interactions in intermetallics: NiAl

The nature of impurity-dislocation interactions is one of the key questions governing the strength and plasticity of solid-solution materials. To investigate the influence of impurities on the mechanical properties of intermetallic NiAl, the electronic structure and energy of NiAl with a <100>{010} edge dislocation and transition-metal impurities was calculated using the real-space tight-binding linear muffin-tin orbital method. The localized electronic states, appearing in the core of the dislocation, are found to lead to strong impurity-dislocation interactions via two mechanisms: firstly, chemical locking, due to strong hybridization between impurity electronic states and dislocation localized states; secondly, electrostatic locking, due to long-range charge oscillations caused by the electron localization in the dislocation core. The results obtained explain qualitatively why the solid-solution hardening effect in NiAl correlates with the electronic structure of impurities rather than with size misfit, as expected according to traditional views.

Low-temperature plasticity of Pb–Bi alloys: the role of thermal activation and inertial effects

Detailed studies of temperature dependences of critical shear stress and strain-rate sensitivity of deforming stress of Pb–Bi single crystals with 0.1–6.0 at. % Bi are carried out in the temperature range 0.5–295 K. The deforming stress decrease during a superconducting transition of the sample is studied and the concentration dependence of the effect is measured. The ideas of a gradual transition (upon cooling) from thermally activated motion of dislocations through impurity barriers to the thermoinertial mechanism in the temperature range 10–25 K and further to the quantum-inertial motion at temperatures ≲1 K are developed. A detailed thermoactivation analysis of experimental data is carried out, and empirical estimates of internal stresses, dislocation–impurity interaction parameters, electron and phonon components of dynamic drag coefficient for dislocations are obtained.

Analysis of Large Impurity Atmospheres at Dislocations and Associated Point Defect Reactions in Differently n-Doped GaAs Crystals

The large impurity atmospheres at dislocations typical of n-type (Si- or Te-doped) GaAs crystals have been analysed by localized measurements of the free electron concentration, diffusion length and DSL etching velocity. The atmospheres always contain dopant atoms as well as point defects (complexes) whose formation and type depend on the type of dopant impurity and melt stoichiometry. The donor- or acceptor-like characteristics of such point defects (complexes) are responsible for the observed remarkable difference in the electrical and recombinative properties of the atmospheres between the differently doped crystals. The point defect reactions at the base of the formation of the slip traces are discussed. The possible mechanisms of the impurity-dislocation interaction leading to the formation of the atmospheres are also considered.

LBIC investigation of impurity-dislocation interaction in FZ silicon wafers

In the present work, dislocation arrays are investigated in float zone (FZ) grown silicon wafers by the light beam induced current (LBIC) mapping technique at different wavelengths and by deep level transient spectroscopy (DLTS). The LBIC technique appears to be able to recognize and to detect these arrays and to evaluate their recombination strength. In FZ dislocated wafers, a phosphorus diffusion attenuates strongly the LBIC contrast of dislocations, depending on the duration and temperature of the treatment. Electrical activity at room temperature of the defects, still physically present, seems to disappear. Simultaneously, the peak intensity of DLTS spectra related to dislocations is reduced and this evolution depends on the phosphorus diffusion temperature and duration.

The effect of electronic localized states at dislocations on the ‘chemical’ impurity-dislocation interaction

Abstract The electronic contribution to the interaction energy between impurities and edge dislocations, which is related to the existence of localized electronic states at the dislocation, is calculated within the framework of a simple model. It is shown that the interaction energy varies within the limits of 10−2−-10−1 of the bandwidth and depends essentially on the lattice structure, the Burgers vector b, the type of impurity (‘donor’ or ‘acceptor’) and on the conduction-band filling. These effects are expected to be important in intermetallics with the B2 structure, where plastic deformation is governed by dislocations with b = a{100) (NiAl, CoAl, etc.).

Effects of strain-rate and ageing at 573 and 973 K on the mechanical (compressive) behaviour of 〈110〉 oriented (‘soft’) NiAl single crystals with and without microalloying additions of Ti, Zr, and Hf. II

The effects of impurity gettering on the mechanical behaviour of NiAl have received extensive attention recently. The present work was directed at static and dynamic strain ageing phenomena and strain-rate sensitivity minima, which are supposed to be related to the dislocation-impurity interactions, for 〈110〉 oriented NiAl single crystals with microalloying additions of Ti, Hf, and Zr as getters (0.1 at.%). The influence of ageing at 573 and at 973 K on compressive properties and microhardness was also investigated. The gettering effects were found to be less pronounced for NiAl + Ti and more pronounced for NiAl + Hf and NiAl + Zr, and the gettering effects lead to marked changes in the strength and ductility behaviour after ageing at 973 K as well as static strain-ageing at 573 K, and to strain-rate sensitivity. The observed effects are believed to be due to the formation of precipitates containing Ti, Hf, or Zr, their coarsening during ageing, and interactions of dislocations with either precipitates and/or solute atoms and interstitials.

Effects of ageing at 673 K on the compressive behaviour of 〈110〉 oriented (‘soft’) NiAl single crystals and polycrystals with and without Ti additions

Since the remarkable increase in room temperature (RT) ductility of 〈110〉 oriented NiAl single crystals by microalloying with Fe, Ga or Mo the effects of microalloying and of impurity gettering on the mechanical behaviour of NiAl are still under discussion. Thus the compressive behaviour of 〈110〉 oriented (‘soft’) NiAl single crystals and polycrystals with and without Ti (up to 0.1 at%), which has long been used as a getter in steel metallurgy, has been studied in detail. In particular, the effects of ageing at 673 K on RT mechanical properties, and static strain-ageing at 673 K, have been investigated. It was found that dislocation-impurity interactions play an important role in the mechanical behaviour of NiAl, and Ti additions may indeed serve as a getter for solute atoms. However, this effect does not lead to improved RT ductility of NiAl. The motion of 〈100〉 dislocations at RT was found to be restricted in single crystals with Ti compared with crystals without Ti. Ageing at 673 K decreases the RT ductility drastically and this is due to the formation of Ti-containing precipitates rather than pinning of mobile dislocations by interstitials. Likewise, the Ti-containing precipitates on dislocations lead to strain-ageing effects at 673 K.

Barrier parameters and statistics controlling the plasticity of Ti‒O solid solutions in the temperature range 20–550 K

Abstract Detailed thermal activation analysis has been carried out on experimental data for the plasticity of polycrystalline titanium containing 0·06–1·6 at.% O in the temperature range 4·2–600 K. The analysis of the dislocation-impurity interaction parameters took into consideration the variations in the shear modulus and internal stress with temperature and the fact that the impurity distribution along dislocations can have various statistics. Values of the energy and maximum force of the dislocation-impurity interaction, the “depth” of the obstacle (the interaction region), the pre-exponential factor in the Arrhenius equation, as well as the average dislocation segment length and the internal stress, have been determined. It has been shown that in the range below 550 K the kinetics of plastic strain in Ti-O alloys are controlled by thermally activated motion of dislocations through barriers formed by oxygen atoms. The specific features of the change in the plasticity parameters of α-Ti usually observe...

EBIC-Investigation of the Dislocation-Impurity Interaction in Silicon

EBIC-Investigation of the Dislocation-Impurity Interaction in Silicon

Study on dislocation–impurity interaction by the Blaha effect

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Dislocation—Impurity Interaction and its Effect on Semiconductor Properties

The results confirming a significant role of dislocation—impurity interaction in changing local properties of plastically deformed semiconductor crystals have been presented.

INTERNAL FRICTION OF DEFORMED NaCL

Internal friction of deformed oriented NaCl single crystal has been measured as a function of flow stress, strain amplitude, frequency, temperature and divalent doping. In pure NaCl after deformation a maximum of internal friction P1 is observed at low temperatures. With increasing Sr2+- doping a second but much weaker peak P2 appears at higher temperatures. The dependencies of the {100} system compares well with that obtained from yield stress measurements. P2 is due to impurity-dislocation interaction.

Electrical Properties and Defect Structure of Plastically Deformed Silicon Crystals Doped with Gold

The effect of a specially chosen impurity (gold) on the electrical properties and structure of dislocations in silicon is investigated. Impurity gettering by dislocations considerably influences the structure and electrical properties of dislocations as well as the electrical properties of the silicon matrix. The complex of methods employed allow to draw conclusions about the possible mechanisms of dislocation-impurity interactions. [Russian Text Ignored].

Effects Induced by Dislocation-Impurity Interaction in GaAs

Effects Induced by Dislocation-Impurity Interaction in GaAs

Point-like impurity-dislocation interactions in smectic A liquid crystals

Abstract The displacement field created in the neighbourhood of a point-like impurity, its self-energy and point-like impurity-dislocation interaction are calculated for a smectic A liquid crystal in the approximation of small deformations. The binding energy of a point defect to an edge dislocation is also estimated. The use of the Peach-Kochler formula as a basis for the calculation of the dislocation interaction with other defects is discussed.

The nature of the change in the conditions for surmounting pinning centers by dislocation in lead at the superconducting transition

The effect of the presence of Sb on the amplitude dependence of ultrasonic attenuation α in the concentration range 1.7×10 −3 to 4.25×10 −1 at % has been studied systematically on Pb single crystals at 1.4 and 4.2 K (superconducting and normal states) and 77 K. The dependence curve shifts toward greater amplitudesU with increasing concentrationC and to smallerU whenT goes from 1.4 to 4.2 K. The shift toward greaterU at the transition to the normal state is observed for all concentrations. The amplitude-independent attenuation α i varies with concentration nonmonotonically: IncreasingC causes α i first to diminish (the minimum atC=0.034 at %) and then to grow. AtC≥0.034at %, α i does not change at the n-s transition. The studies suggest that the damping factor for dislocations in impure crystals practically does not change at the superconducting transition. Here the damping is essentially due to the dynamic dislocation-impurity interaction. The change in the conditions for a dislocation surmounting the pinning centers at the superconducting transition is determined by the quasistatic mechanism of lowering barriers.