An H plasma has a remarkable effect on dislocation mobility in silicon, reducing its activation energy to 1.2 eV. Applying density functional theory to the interactions of H and H2 with the core of the 90 degrees partial dislocation in Si, we have identified a path for motion involving kink formation and migration at hydrogenated core bonds which conforms exactly to the experimentally measured ...

Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Bas...

Size effects at initial yield (prior to stage II) of idealized micron-sized specimens are modeled within a continuum model of plasticity. Two different aspects are considered: specification of a density of dislocation sources that represent the emission of dislocation dipoles, and the presence of an initial, spatially inhomogeneous excess dislocation content. Discreteness of the source distribu...

Metals with a high density of nanometre-scale twins have demonstrated simultaneous high strength and good ductility, attributed to the interaction between lattice dislocations and twin boundaries. Maximum strength was observed at a critical twin lamella spacing (∼15 nm) by mechanical testing; hence, an explanation of how twin lamella spacing influences dislocation behaviours is desired. Here, w...

Crystals with spatial variations in their axes naturally evolve into cells or grains separated by sharp walls. At high temperatures, polycrystalline grains form from the melt and coarsen with time: the dislocations can both climb and glide. At low temperatures under shear the dislocations (which allow only glide) form into cell structures. We present here a mesoscale theory of dislocation motio...

This thesis consists of two parts. The first part explores a 2-d edge dislocation model to demonstrate characteristics of Field Dislocation Mechanics (FDM) in modeling single and collective behavior of individual dislocations. The second work explores the possibility of modelling adiabatic shear bands propagation within the timespace averaged framework of Mesoscopic Field Dislocation Mechanics ...

We investigate the T (3)-gauge theory of static dislocations in continuous solids. We use the most general linear constitutive relations bilinear in the elastic distortion tensor and dislocation density tensor for the force and pseudomoment stresses of an isotropic solid. The constitutive relations contain six material parameters. In this theory both the force and pseudomoment stresses are asym...

Separation by implanted oxygen (SIMOX) material has proven to provide an extended temperature range (up to 500°C) of operation for partially depleted silicon-on-insulator (SOI) test structures and product circuits in both transportation and communication applications. Such high temperature use is possible due to the built-in dielectric isolation which eliminates the isolation junction and its a...

We have eliminated interface defects from the mismatched Ino.()S GaO 95 As/ (001) GaAs interface by controlling the size of the growth area. 2-Jim-high pillars with different lateral shapes and dimensions were defined within the GaAs substrate before the molecular beam epitaxial growth of 3500 A of Ino.05 Gao,!" As, greater than four times the critical thickness. On the pillars, the linear dens...