Grain boundaries were studied, in high-quality polycrystalline B-doped chemical vapour deposited films, by means of transmission electron microscopy. The samples were grown mainly in <110> or <211> growth directions, and the B doping was of the order of 1018/cm3. Selected-area diffraction was studied, for each grain in a cluster, in order to deduced the relative misorientations. Examples of Σ3, Σ9 and Σ27 coincident-site lattice grain boundaries were found, and these combined to form symmetrical and asymmetrical tri-junctions, quadri- and penta-junctions. Three different types of symmetrical tri-junction were identified; one of which (obtuse tri-junction) had a previously unreported but very high defect density. Another tri-junction (Σ3, Σ9 and Σ27) often occurred in the dissociation of higher junctions (4- and 5-fold junction). The 2 different growth directions led to different types of junction.

Grain Boundaries in Boron-Doped CVD Diamond Films. A.E.Mora, J.W.Steeds, J.E.Butler: Diamond and Related Materials, 2002, 11[3-6], 697-702