Papers by Keyword: Annealing Behaviour

Abstract: Wide band gap semiconductors, mainly GaN, have experienced much attention due to their application in photonic devices and high-power or high-temperature electronic devices. Especially the synthesis of InxGa1-xN alloys has been studied extensively because of their use in LEDs and laser diodes. Here, In is added during the growth process and devices are already very successful on a commercial scale. Indium in nitride ternary and quaternary alloys plays a special role; however, the mechanisms leading to more efficient light emission in In-containing nitrides are still under debate. Therefore, the behaviour of In in GaN and AlN, the nitride semiconductor with the largest bandgap is an important field of study. In is also an important impurity in another wide band gap semiconductor – the II-VI compound ZnO where it acts as an n-type dopant. In this context the perturbed angular correlation technique using implantation of the probe ¹¹¹In is a unique tool to study the immediate lattice environment of In in the wurtzite lattice of these wide band gap semiconductors. For the production of GaN and ZnO based electronic circuits one would normally apply the ion implantation technique, which is the most widely used method for selective area doping of semiconductors like Si and GaAs. However, this technique suffers from the fact that it invariably produces severe lattice damage in the implanted region, which in nitride semiconductors has been found to be very difficult to recover by annealing. The perturbed angular correlation technique is employed to monitor the damage recovery around implanted atoms and the properties of hitherto known impurity – defect complexes will be described and compared to proposed structure models.

Abstract: There are many works on annealing process of SPDed bulk metals but there are limited works on annealing process of SPDed sheets. Therefore, in this study the annealing response after constrained groove pressing (CGP) of low carbon steel sheets has been investigated. These sheets are subjected to severe plastic deformation at room temperature by CGP method up to three passes. Nano-structured low carbon steel sheets produced by severe plastic deformation are annealed at temperature range of 100 to 600 °C for 20 min. The microstructural changes after deformation and annealing are studied by optical microscopy. The effects of CGP strain and annealing temperature on microstructure, strength and hardness evolutions of the nano-scale grained low carbon steel are examined. The results show that annealing phenomena can effectively improve the elongation of process sheets with preserving the hardness and mechanical strength. Also, a thermal stability of microstructure can be observed with annealing at a temperature range of 375–425 °C and 400 °C is achieved as an optimum annealing temperature. Microstructure after post-annealing at temperatures of higher than 600 °C shows abnormal grain growth.

Abstract: µ-Raman measurements were carried out on hydrogen implanted, plasma hydrogenated and subsequently annealed Cz Silicon samples, respectively. In comparison to as-implanted or asplasma treated samples, in consideration of the thermal evolution, the effects of the implanted and subsequently plasma treated samples were analyzed. An enhanced trapping of molecular hydrogen in multivacancies has been observed after hydrogen implantation and subsequent plasma hydrogenation. In comparison to as-implanted samples, the intensity of the local vibrational modes (LVM) of vacancy-hydrogen complexes and silicon-hydrogen bonds are increasing.

Abstract: Several Fe – O samples containing different fractions of dispersed oxides were processed by mechanical milling followed by consolidating rolling. The samples were annealed at 1000oC and then compressed to strains of 0.35, 1.2, and 1.9 at an ambient temperature. Dispersed oxides with size of about 20 nm were homogeneously distributed throughout the ferrite matrix and their volume fractions varied from about 0.3% to 2.0%. To study the annealing softening mechanisms, the coldworked specimens were annealed for an hour at 700oC and 800oC. The fine dispersion of oxide particles was very effective to suppress any softening processes. Primary recrystallization fully developed in the samples with volume fraction of dispersed oxides of about 0.3%. Increase in the fraction of dispersed oxides resulted in decrease of the fraction recrystallized. In the samples containing 2.0 vol.% of dispersed oxides, only recovery was the annealing softening process irrespective of the preceding cold strain. The critical volume fraction of dispersed particles for development of the primary recrystallization is considered to range from 0.5 to 2.0%.