Дефектная структура слоев GaAs, имплантированных ионами азота

Structural defects formed in epitaxial GaAs layers as a result of 250-keV N^+ ion implantation to doses within 5 × 10^14–5 × 10^16 cm^–2 have been studied by the X-ray diffraction (XRD) and transmission electron microscopy techniques. No amorphization of the ion-implanted layer took place in the entire dose range studied. The implantation to doses of 5 × 10^14 and 5 × 10^15 cm^–2 led to the appearance of an additional peak on XRD curves, which was related to the formation of a stressed GaAs layer with positive deformation arising due to the formation of point-defect clusters. The implantation to a dose of 5 × 10^16 cm^–2 led to the formation of a dense structure of extended defects in the implanted layer, which was accompanied by the relaxation of macrostresses to the initial state.

Coordination Spheres Effect On RecompositionAtoms In AB Alloys

This study focused on the variation of the long-range order parameters with temperature for nine coordination spheres. The computer simulation results showed several mechanismsof atoms disordering. These mechanisms are represented in: (Substitution point defect, Clusters and Segregations, Micro domain, Antiphase order and Antiphase boundaries. As the number of coordination spheres increase, the interatomic interaction increase with a decrease in the ordered phase stability. In the initial stages of the computer simulation two phases in the alloy is found, an ordered phase of long-range order and ordered phase of antiphase domain. In final stages an ordered phase of short –range order is found.

Point Defect Clusters Induced by High-Speed Deformation and its Effect on Age-Hardening in 6061 Aluminum Alloys

Effects of high-speed deformation on age hardening and microstructural evolution behavior of 6061 aluminum alloys were studied. By affecting the high-speed impact compression (about 5 GPa) to the 6061 aluminum alloy plate in the state of quenching after the solution heat treatment, the maximum hardness became twice as high as the original hardness. Even after the impact compression, age-hardening was clearly identified both at 175 °C and 100 °C. TEM observation revealed that point defect clusters were distributed densely inside grains after the impact compression, possibly due to the effect of high-speed deformation. The point defect clusters observed were assumed to be stacking fault tetrahedra on the basis of high resolution TEM analysis. The point defect clusters and precipitates were both visible even after the peak-aged condition at 175 °C. The 6061 aluminum alloy specimen after the solution heat treatment, followed by the impact compression (8.0 GPa) and the peak-aged condition showed the highest hardness value (154 Hv) among the testing conditions selected in the present study.

Application of Density Functional Theory to Point Defect Anelasticity of Carbon-Containing Austenitic Alloys

We have used density functional theory (DFT) to determine binding energies (BE’s) of carbon-vacancy (C-v) point-defect complexes of probable importance to C-based anelastic relaxation processes in fcc iron alloys. Calculations are presented for three types of stable point defect clusters: C-v pairs, di-C-v triplets, and tri-C-v quadruplets. We demonstrate semi-quantitative consistency of the calculated BE’s with internal friction results on Fe-36%Ni-C alloys. The BE’s, which are in the range-0.37 eV to-0.64 eV, were determined for a hypothetical non-magnetic (NM) fcc Fe. The effect of the magnetic state of fcc Fe on some of these quantities was investigated by DFT and is shown to be significant; the BE’s appear to be reduced in antiferromagnetic (AFM) fcc Fe.

Point Defect Clusters and Dislocations in FIB Irradiated Nanocrystalline Aluminum Films: An Electron Tomography and Aberration-Corrected High-Resolution ADF-STEM Study

Focused ion beam (FIB) induced damage in nanocrystalline Al thin films has been characterized using advanced transmission electron microscopy techniques. Electron tomography was used to analyze the three-dimensional distribution of point defect clusters induced by FIB milling, as well as their interaction with preexisting dislocations generated by internal stresses in the Al films. The atomic structure of interstitial Frank loops induced by irradiation, as well as the core structure of Frank dislocations, has been resolved with aberration-corrected high-resolution annular dark-field scanning TEM. The combination of both techniques constitutes a powerful tool for the study of the intrinsic structural properties of point defect clusters as well as the interaction of these defects with preexisting or deformation dislocations in irradiated bulk or nanostructured materials.

Investigation of Germanium Implanted with Hydrogen for Layer Transfer Applications

The technology for thin Ge layer transfer by hydrogen ion-cut process is characterised in this work. Experiments were carried out to determine suitable hydrogen ion implantation doses in germanium for the low temperature ion cut process by examining the formation of blisters on implanted samples. Raman and Spreading Resistance Profiling (SRP) have been used to analyse defects in germanium caused by hydrogen implants. Bevelling has been used to facilitate probing beyond the laser penetration depth. Results of Raman mapping along the projection area reveal that after post implant annealing at 400 °C, some crystal damage remains, while at 600 °C, the crystal damage has been repaired. SRP shows that some amount of hydrogen acceptor states (~1Î1016 acceptors/cm2) remain after 600 °C. These are thought to be vacancy-related point defect clusters.