Models of activated recrystallization on isolated grain boundaries in polycrystals

New phenomenological models of recrystallization of a polycrystalline material in two regimes are proposed taking into account the finite width of grain boundaries. The solutions are obtained in an analytical form for the initial-boundary value problems formulated. They describe the distributions of the concentration of impurities diffusing from the surface coating, both in the grain boundary and in the grain itself in the recrystallized region. The speed of the recrystallization front movement is indicated, which agrees with the types of the corresponding kinetic dependences observed in experiments.

Disorientation Relations during the Early Stages of Recrystallization in Medium and Low SFE fcc Metals

The objective of this paper is to identify the predominant crystallographic relations between deformed state and recrystallized grains during the early stages of recrystallization of fcc metals with medium and low stacking fault energy. The experimental investigations, based on SEM/EBSD measurements, have focused on the transformations which occur in plane strain compressed single crystals with stable orientations. After annealing the disorientation across the recrystallization front 'defines' the final rotation by angles in the ranges of 25-35oand 45-55oaround axes mostly grouped near the <122>, <012>, <112> and <111> directions located around the normals of all four {111} slip planes.

A Comprehensive Atomistic Kinetic Monte Carlo Model for Amorphization/Recrystallization and its Effects on Dopants

ABSTRACTThis work shows a comprehensive atomistic model to describe amorphization and recrystallization, and its different effects on dopants in silicon. We begin by describing the physical basis of the model used, based on the transformation of ion-implanted dopants and generated point defects into amorphous pockets of different sizes. The growth and dissolution of amorphous pockets is simulated by the capture and recombination of point defects with different activation energies. In some cases, this growth leads to the formation of amorphous layers. These layers, composed of a set of amorphous elements, have an activation energy to be recrystallized. The recrystallization velocity is modeled not only depending on temperature, but also on dopant concentration. During the recrystallization, dopants move with the recrystallization front to simulate the dopant redistribution during solid phase epitaxial regrowth (SPER). At the edge of the amorphous-crystalline interface, the remaining damage forms end-of-range (EOR) defects.Once the model is explained, we discuss the calibration methodology used to reproduce several amorphous/crystalline (A/C) experiments, including the dependencies of the A/C transition temperature on dose rate and ion mass, and the A/C depth on ion implant energy.This calibrated model allows us to explore the redistribution of several dopants, including B, As, F, and In, during SPER. Experimental results for all these dopants are compared with relevant simulations.

An Update on the Geology of the Lupin Gold Mine, Nunavut, Canada

The Lupin mine, located in the central Slave province just east of the western boundary of Nunavut Territory, is a world-class example of a Neoarchean-aged banded iron formation (BIF)-hosted lode-gold deposit. At the minesite the gold-mineralized Lupin BIF, separating stratigraphically underlying psammitic wacke and overlying argillaceous turbidite sequences, delineates the Lupin dome, a hammerhead-shaped F2/F3 interference fold structure occurring at the greenschist to amphibolite facies metamorphic transition within the thermal aureole of the Contwoyto batholith. Detailed paragenetic relationships indicate that peak thermal metamorphism coincided with the switch from regional D2 compression to rapid D3 unroofing of the Neoarchean orogenic infrastructure. Gold initially precipitated with pyrrhotite, replacing amphibolitic BIF at the apex of the Lupin deformation zone, separating the east and west lobes of the Contwoyto batholith. Over the course of associated prograde/retrograde metasomatic overprints, gold was further remobilized during garnet and loellingite/arsenopyrite growth in chlorite-altered selvages of late-forming ladder quartz veins. A metamorphic model of ore genesis, with gold being scavenged and transported by metamorphic fluid that was shed and structurally trapped at the amphibolite recrystallization front, is favored over the previously proposed syngenetic and exogenic models of gold concentration that have tended to polarize genetic interpretations to date.

Spontaneous Crystalline Multilayer Formation in Ni Implanted Al at 100 K

The microstructure evolution of aluminum implanted with nickel at 5 MeV and at 100 K to a local concentration of 25 at. % is described. Transmission Electron Microscopy (TEM) observa- tions and Rutherford Backscattering Spectrometry (RBS) experiments are conducted to deter-mine the Ni profile and the microstructure of the implanted samples. For lower Ni concentration, it has been previously observed that Al0.75Ni0.25 amorphous precipitates are formed together with a high dislocation density. When the Ni concentration reaches 25 at. %, a new crystalline multi-layered microstructure is observed: the TEM observations reveal the presence of well-defined crystalline layers separated by sharp interfaces. To our knowledge, it is the first time that such a structure is observed without further annealing of the implanted sample. A series of mechanisms describing the formation of the crystalline multilayer are briefly discussed. It is argued that its formation is the result of a recrystallization front produced by the exothermal amorphous to crystal transformation.

High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties

High-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350°C and 550°C to a fluence of 1015 cm−2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation.In the samples implanted at 350°C Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600° showed that the solid phase epitaxial regrowth of the damaged layers strongly depends on both the Ge concentration in the alloys and the temperature of annealing. Along with the recrystallization of the damaged matrix, annealing was observed to induce simultaneous removal of nearly all the implanted Er as the recrystallization front progresses towards the surface.In contrast, high temperature implantation at 550°C led to spontaneous recovery of the alloy crystallinity and incorporation of considerable fraction of implanted Er atoms on regular tetrahedral interstitial sites in the host lattice.