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 plasm a-assisted chemical vapour deposition (CVD) of diamond films is reported. T hese particular twinning centres have been identified by ultra-high resolut ion electron microscopy at 0.12 nm resolution, with the help of image calcu lations. Plausible three-dimensional atomic-scale models are proposed for t wo 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 fivefol d twin centres and associated structural units, which are quite representat ive of the growth defects observed in CVD diamond, have been reported. (C) 2000 Elsevier Science S.A. All rights reserved.