The use of heteroepitaxy in the fabrication of bicrystals for the study of grain boundary structure

Abstract

Experiments on grain boundary structure can be grouped into two categories - those that provide limited structural information on a large number of boundaries and those that give detailed structural information on a limited sampling of boundaries. The first category is typified by the elegant Rotating-Sphere-On-Plate experiments. In this technique single crystal spheres are placed in a random array on a single crystal plate and annealed to promote their relaxation into low-energy orientations. The resulting orientation distribution is recorded in an X-ray pole figure and, assuming all boundary planes are parallel to the plate surface, statistically significant data on misorientation and type of boundary (twist/tilt, symmetrical/asymmetrical) can be obtained rapidly. However, this macroscopic method does not give any direct information on the grain boundary structure. At the other extreme, detailed investigations of the structure of individual grain boundaries have been carried out using transmission electron microscopy. High-resolution observations have revealed the atomic structure of special grain boundaries in semiconductors, and ceramics, but the difficulty of sample preparation has severely limited the number of experimental analyses of such boundaries. Until quite recently an additional problem hindering the study of the close-packed structure of metals has been the resolution limit of availablemore » microscopes. Thus only a few examples of the detailed grain boundary structure in metals have been reported.« less