Abstract
Thick samples of boron-doped chemically vapour-deposited diamond have been studied in plan view, by taper section and in cross-section by transmission electron microscopy. Dislocations, nanotwins and grain boundaries have been investigated by diffraction contrast techniques and reasons have been found for their introduction during the growth process. The observations have been correlated with others at lower magnification by scanning electron microscopy and as a result the nature and importance of grain clusters have become apparent. In addition it has been found that (110) growth favours the introduction of geometrically determined stresses and related defects while in (112) growth these effects are greatly reduced. However, (110) growth produces equiaxed grain clusters but (112) growth generates elongated grain clusters.