GaN films are grown by plasma-assisted molecular beam epitaxy on 6H-SiC(0001) substrates. Suitable substrate preparation and growth conditions are found which greatly improve the structural quality of the films. Threading dislocation densities of about 1 10 cm for edge dislocations and 1 10 cm for screw dislocations are achieved in GaN films of 1 m thickness grown under optimal conditions. Reve...

ÐThe e€ect of hydrogen on the interaction between dislocations and other elastic centers (impurity atoms and dislocations) in 310 S stainless steel and high-purity aluminum has been directly observed during deformation experiments in situ in an environmental cell transmission electron microscope. In 310 S stainless steel, the presence of hydrogen was observed to reduce the elastic interactions ...

We have studied three-dimensional (3D) configurations of dislocations in the β phase of a Ti-35mass%Nb alloy by means of single-axis tilt tomography using bright-field scanning transmission electron microscopy (BF-STEM). To visualize dislocations, the hh0 systematic reflections were excited throughout tilt-series acquisition with the maximum tilt angle of 70°. Dislocations in the β grains were ...

-Equilibrium distributions of collections of discrete dislocations are analyzed, with the dislocations modelled as line defects in a linear elastic medium. The dislocated equilibrium configuration is determined by finding a minimum potential energy configuration, with respect to variations in the dislocation positions, for a fixed number and type of dislocations. Numerical results are presented...

A dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials. The theory was originally developed by Vito Volterra in 1905, but the term 'dislocation' was not coined until later by the Professor Sir Frederick Charles Frank of the Physics Department at the University of Bristol. In 19...

Deformation mechanisms of a fully lamellar TiAl (γ lamellae: 100 ~ 300Ênm thick, α2 lamellae: 10 ~ 50 nm thick) crept at 760¡C have been investigated. It was found that, as a result of a fine structure, the motion and multiplication of dislocations within both γ and α2 lamellae are limited at low creep stresses (< 400 MPa). Thus, the glide and climb of lattice dislocations have insignificant co...