Ultra-high resolution electron microscopy investigation of growth defects in CVD diamond films: twin interactions and fivefold twin centres

An elucidation of the core structure of fivefold twin centres arising from the interaction between less than five first-order twin boundaries in plasma-assisted chemical vapour deposition (CVD) of diamond films is reported. These particular twinning centres have been identified by ultra-high resolution electron microscopy at 0.12 nm resolution, with the help of image calculations. Plausible three-dimensional atomic-scale models are proposed for two specific structural variants, which have been found closely connected to high-order twin boundaries via original heptagonal or octagonal structural units. To our knowledge, this is the first time that such types of fivefold twin centres and associated structural units, which are quite representative of the growth defects observed in CVD diamond, have been reported. (C) 2000 Elsevier Science S.A. All rights reserved.