Showing papers by "William A.T. Clark published in 1995"

Grain boundary dislocations in a Σ13 grain boundary in silicon. I. Analysis of the possible grain boundary structures and dislocations

Abstract: The purpose of this paper is to describe the different grain boundary structures and kinds of dislocations which can arise in the {510} Σ13 grain boundary in diamond cubic materials. Firstly, the different possible grain boundary structures are derived within the framework of group theory, and then general expressions for the Burgers vectors of the grain boundary dislocations which separate these structures are obtained. These grain boundary dislocations are of three kinds: (1) perfect grain boundary dislocations (also called DSC dislocations), which do not change the grain boundary structure, (2) imperfect grain boundary dislocations, which relate different, but equivalent, grain boundary structures, and finally (3) partial dislocations, which separate two non-equivalent grain boundary structures. Transmission electron microscopy is then used to show that imperfect dislocations are indeed present in a Σ13 (22·6°/[001]½) grain boundary in Si, and have Burgers vectors consistent with ¼[001]½.

Dislocation boundary interactions in a Σ13 grain boundary in silicon. II. Grain boundary structures and dislocations produced during deformation

Abstract: A Σ13, 22·6°/[001]½, grain boundary in Si with plastically deformed at 850°C under a range of loading orientations and strains. The resulting deformation was characterized in the transmission electron microscope, including the determination of the operating slip systems, and the Burgers vectors of the various grain boundary dislocations produced. For small strains, the observed grain boundary dislocations are consistent with a dissociation reaction in the boundary of the incoming crystal dislocations to produce two ¼⟨111⟩ partial grain boundary dislocations. This provides a good compromise between the overall reduction in elastic strain energy and the increase in step height area in the boundary. As deformation proceeds, the different sets of grain boundary dislocations interact and further dissociate, so that a new network of grain boundary dislocations is produced. Finally, partial dislocations having a ⅛ component along the [001]½ disorientation axis are also observed.